91
Source enumeration and robust voice activity detection in wireless acoustic sensor networks
(Tanuj Hasija, Martin Gölz, Michael Muma, Peter J Schreier and Abdelhak M Zoubir)
Proc. Asilomar Conf. on Signals, Systems, Computers, 2019. [BibTeX]
@inproceedings{hasijasource,
author = {Hasija, Tanuj and G{\"o}lz, Martin and Muma, Michael and Schreier, Peter J and Zoubir, Abdelhak M},
booktitle = {Proc. Asilomar Conf. on Signals, Systems, Computers},
title = {Source enumeration and robust voice activity detection in wireless acoustic sensor networks},
year = {2019},
}
[Abstract]
92
Two-channel passive detection exploiting cyclostationarity(
Stefanie Horstmann,
David Ram'irez and Peter J. Schreier)
Proc. 27th European Signal Proc. Conf. (EUSIPCO),
A Coru~na, Spain,
2019.DOI:10.23919/EUSIPCO.2019.8902989. [BibTeX]
@inproceedings{Horstmann2019,
address = {A Coru\~{n}a, Spain},
author = {Horstmann, Stefanie and Ram{\'{i}}rez, David and Schreier, Peter J.},
booktitle = {Proc. 27th European Signal Proc. Conf. (EUSIPCO)},
title = {Two-channel passive detection exploiting cyclostationarity},
year = {2019},
doi = {10.23919/EUSIPCO.2019.8902989},
}
[Abstract] 93
Estimating the number of correlated components based on random projections
(Christian Lameiro, Tanuj Hasija, Tim Marrinan and Peter J Schreier)
ICASSP 2019-2019 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pp. 5152–5156, 2019. [BibTeX]
@inproceedings{lameiro2019estimating,
author = {Lameiro, Christian and Hasija, Tanuj and Marrinan, Tim and Schreier, Peter J},
booktitle = {ICASSP 2019-2019 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)},
title = {Estimating the number of correlated components based on random projections},
year = {2019},
pages = {5152–5156},
}
[Abstract]
94
Benefits of improper signaling for overlay cognitive radio
(Christian Lameiro, Ignacio Santamaria and Peter J Schreier)
Proc. Globecom, 2019. [BibTeX]
@inproceedings{lameirobenefits,
author = {Lameiro, Christian and Santamar{\i}a, Ignacio and Schreier, Peter J},
booktitle = {Proc. Globecom},
title = {Benefits of improper signaling for overlay cognitive radio},
year = {2019},
}
[Abstract]
95
Improper gaussian signaling for the two-user broadcast channel treating interference as noise
(Christian Lameiro, Ignacio Santamaria and Peter J Schreier)
ICASSP 2019-2019 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pp. 4829–4833, 2019. [BibTeX]
@inproceedings{lameiro2019improper,
author = {Lameiro, Christian and Santamaria, Ignacio and Schreier, Peter J},
booktitle = {ICASSP 2019-2019 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)},
title = {Improper gaussian signaling for the two-user broadcast channel treating interference as noise},
year = {2019},
pages = {4829–4833},
}
[Abstract]
96
Two-channel passive detection of cyclostationary signals in noise with spatio-temporal structure
(Stefanie Horstmann, David Ramírez, Peter J. Schreier and Aaron Pries)
Proc. Asilomar Conf. Signals Syst. Computers, Pacific Grove, CA, USA, November 2019. [BibTeX]
@inproceedings{Horstmann20192,
address = {Pacific Grove, CA, USA},
author = {Horstmann, Stefanie and Ram{\'i}rez, David and Schreier, Peter J. and Pries, Aaron},
booktitle = {{P}roc.\ {A}silomar {C}onf.\ {S}ignals\ {S}yst. {C}omputers},
month = {{N}ovember},
title = {Two-channel passive detection of cyclostationary signals in noise with spatio-temporal structure},
year = {2019},
}
[Abstract]
97
Energy-Efficient Improper Signaling for K-User interference channels(
Mohammad Soleymani,
Christian Lameiro,
Ignacio Santamaria and Peter J. Schreier)
Proc. IEEE European Signal Processing Conference (EUSIPCO),
pp. 1409–1413,
A Coruna, Spain,
September 2019.DOI:10.23919/EUSIPCO.2019.8903023. [BibTeX]
@inproceedings{Sole1909:Energy,
address = {A Coruna, Spain},
author = {Soleymani, Mohammad and Lameiro, Christian and Santamaria, Ignacio and Schreier, Peter J.},
booktitle = {Proc. IEEE European Signal Processing Conference (EUSIPCO)},
month = {September},
title = {{Energy-Efficient} Improper Signaling for {$K$-User} interference channels},
year = {2019},
pages = {1409–1413},
doi = {10.23919/EUSIPCO.2019.8903023},
}
[Abstract] 98
Rate analysis of SC-FDE and OFDM Systems with Low Resolution ADCs(
Mohammad Soleymani and Behrouz Maham)
Proc. IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC),
pp. 351–355,
Istanbul, Turkey,
September 2019.DOI:10.1109/PIMRC.2019.8904363. [BibTeX]
@inproceedings{Sole1909:Rate,
address = {Istanbul, Turkey},
author = {Soleymani, Mohammad and Maham, Behrouz},
booktitle = {Proc. IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)},
month = {September},
title = {Rate analysis of {SC-FDE} and {OFDM} Systems with Low Resolution {ADCs}},
year = {2019},
pages = {351–355},
doi = {10.1109/PIMRC.2019.8904363},
}
[Abstract] 99
Energy-efficient design for underlay cognitive radio using improper signaling(
Mohammad Soleymani,
Christian Lameiro,
Peter J Schreier and Ignacio Santamaria)
IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP),
pp. 4769–4773,
Brighton, England,
May 2019.DOI:10.1109/ICASSP.2019.8683029. [BibTeX]
@inproceedings{soleymani2019energy,
address = {Brighton, England},
author = {Soleymani, Mohammad and Lameiro, Christian and Schreier, Peter J and Santamaria, Ignacio},
booktitle = {IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)},
month = {May},
title = {Energy-efficient design for underlay cognitive radio using improper signaling},
year = {2019},
pages = {4769–4773},
doi = {10.1109/ICASSP.2019.8683029},
}
[Abstract] 100
Model-order selection in statistical shape models(
A. Eguizabal,
P. J. Schreier and D. Ramírez)
2018 IEEE 28th International Workshop on Machine Learning for Signal Processing (MLSP),
pp. 1–6,
Sep. 2018.DOI:10.1109/MLSP.2018.8516941. [BibTeX]
@inproceedings{Eguizabal18,
author = {A. Eguizabal and P. J. Schreier and D. Ramírez},
booktitle = {2018 IEEE 28th International Workshop on Machine Learning for Signal Processing (MLSP)},
month = {Sep.},
title = {Model-order selection in statistical shape models},
year = {2018},
pages = {1–6},
doi = {10.1109/MLSP.2018.8516941},
}
[Abstract] 101
Deep learning for object detection in fine-art paintings
(S. Smirnov and A. Eguizabal)
2018 IEEE International Conference on Metrology for Archaeology and Cultural Heritage, Sep. 2018. [BibTeX]
@inproceedings{MetroArchaeo18,
author = {S. Smirnov and A. Eguizabal},
booktitle = {2018 IEEE International Conference on Metrology for Archaeology and Cultural Heritage},
month = {Sep.},
title = {Deep learning for object detection in fine-art paintings},
year = {2018},
}
[Abstract]
102
Complete model selection in multiset canonical correlation analysis
(T. Marrinan, T. Hasija, C. Lameiro and P. J. Schreier)
Proc. European Signal Process. Conf. (EUSIPCO), pp. 1082–1086, September 2018. [BibTeX]
@inproceedings{MarrinanEusipco18,
author = {T. Marrinan and T. Hasija and C. Lameiro and P. J. Schreier},
booktitle = {Proc. European Signal Process. Conf. (EUSIPCO)},
month = {September},
title = {Complete model selection in multiset canonical correlation analysis},
year = {2018},
pages = {1082–1086},
}
[Abstract]
103
Regularized lattice reduction-aided ordered successive interference cancellation for MIMO detection
(J. Tong, Q. Guo, J. Xi, Y. Yu and P. J. Schreier)
Proc. IEEE Workshop on Statistical Signal Processing, Freiburg, Germany, June 2018. [BibTeX]
@inproceedings{Tong:2018aa,
address = {Freiburg, Germany},
author = {J. Tong and Q. Guo and J. Xi and Y. Yu and P. J. Schreier},
booktitle = {Proc. IEEE Workshop on Statistical Signal Processing},
month = {{J}une},
title = {Regularized lattice reduction-aided ordered successive interference cancellation for {MIMO} detection},
year = {2018},
}
[Abstract]
104
Improper signaling for OFDM underlay cognitive radio systems(
Mohammad Soleymani,
Christian Lameiro,
Peter J. Schreier and Ignacio Santamaría)
Proc. IEEE Statistical Signal Processing Workshop (SSP),
pp. 722–726,
Freiburg, Germany,
June 2018.DOI:10.1109/SSP.2018.8450843. [BibTeX]
@inproceedings{SoleymaniSSP18,
address = {Freiburg, Germany},
author = {Mohammad Soleymani and Lameiro, Christian and Schreier, Peter J. and Santamar{\'i}a, Ignacio},
booktitle = {Proc. IEEE Statistical Signal Processing Workshop (SSP)},
month = {June},
title = {Improper signaling for {OFDM} underlay cognitive radio systems},
year = {2018},
pages = {722–726},
doi = {10.1109/SSP.2018.8450843},
}
[Abstract] 105
Performance analysis of maximally improper signaling for multiple-antenna systems
(Christian Lameiro, Ignacio Santamaria and Peter J. Schreier)
Proc. IEEE Wireless Comm. Networking Conf. (WCNC), Barcelona, Spain, April 2018. [BibTeX]
@inproceedings{Lameiro:2018aa,
address = {Barcelona, Spain},
author = {Lameiro, Christian and Santamaria, Ignacio and Schreier, Peter J.},
booktitle = {Proc. IEEE Wireless Comm. Networking Conf. (WCNC)},
month = {April},
title = {Performance analysis of maximally improper signaling for multiple-antenna systems},
year = {2018},
}
[Abstract]
106
A weighting strategy for active shape models
(Alma Eguizabal and Peter J. Schreier)
IEEE International Conference on Image Processing 2017, 2017. [BibTeX]
@inproceedings{eguizabal2017weighting,
author = {Eguizabal, Alma and Schreier, Peter J.},
booktitle = {IEEE International Conference on Image Processing 2017},
title = {A weighting strategy for active shape models},
year = {2017},
}
[Abstract]
107
Constrained subspace estimation via convex optimization.
(Igancia Santamaria, Javier Via, Michael Kirby, Tim Marrinan, Chris Peterson and Louis Scharf)
25th European Signal Processing Conference (EUSIPCO), pp. 1200–1204, 2017. [BibTeX]
@inproceedings{santamariaConstrained2017,
author = {Santamaria, Igancia and Via, Javier and Kirby, Michael and Marrinan, Tim and Peterson, Chris and Scharf, Louis},
booktitle = {25th European Signal Processing Conference (EUSIPCO)},
title = {Constrained subspace estimation via convex optimization.},
year = {2017},
pages = {1200–1204},
}
[Abstract]
108
Detection of almost-cyclostationarity: an approach based on a multiple hypothesis test(
Stefanie Horstmann,
David Ramírez and Peter J. Schreier)
Proc. Asilomar Conf. Signals Syst. Computers,
pp. 1635–1639,
Pacific Grove, CA, USA,
October 2017.DOI:10.1109/ACSSC.2017.8335636. [BibTeX]
@inproceedings{Horstmann2017,
address = {Pacific Grove, CA, USA},
author = {Horstmann, Stefanie and Ram{\'i}rez, David and Schreier, Peter J.},
booktitle = {{P}roc.\ {A}silomar {C}onf.\ {S}ignals\ {S}yst. {C}omputers},
month = {{O}ctober},
title = {Detection of almost-cyclostationarity: an approach based on a multiple hypothesis test},
year = {2017},
pages = {1635–1639},
doi = {10.1109/ACSSC.2017.8335636},
}
[Abstract] 109
A sparse CCA algorithm with application to model-order selection for small sample support(
C. Lameiro and P. J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 4721–4725,
New Orleans, USA,
March 2017.DOI:10.1109/ICASSP.2017.7953052. [BibTeX]
@inproceedings{Lameiro:2017df,
address = {New Orleans, USA},
author = {C. Lameiro and P. J. Schreier},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {March},
title = {A sparse {CCA} algorithm with application to model-order selection for small sample support},
year = {2017},
pages = {4721–4725},
doi = {10.1109/ICASSP.2017.7953052},
}
[Abstract] 110
Adaptive visual sort and summary of micrographic images of nanoparticles for forensic analysis(
Elizabeth Jurrus,
Nathan Hodas,
Nathan Baker,
Tim Marrinan and Mark D Hoover)
Technologies for Homeland Security (HST), 2016 IEEE Symposium on,
pp. 1–6,
2016.DOI:10.1109/THS.2016.7568959. [BibTeX]
@inproceedings{jurrusHST,
author = {Jurrus, Elizabeth and Hodas, Nathan and Baker, Nathan and Marrinan, Tim and Hoover, Mark D},
booktitle = {Technologies for Homeland Security (HST), 2016 IEEE Symposium on},
title = {Adaptive visual sort and summary of micrographic images of nanoparticles for forensic analysis},
year = {2016},
pages = {1–6},
doi = {10.1109/THS.2016.7568959},
}
[Abstract] 111
Flag-based detection of weak gas signatures in long-wave infrared hyperspectral image sequences.(
Tim Marrinan,
J. Ross Beveridge,
Bruce Draper,
Michael Kirby and Chris Peterson)
SPIE Defense, Security, and Sensing,
2016.DOI:10.1117/12.2224117. [BibTeX]
@inproceedings{marrinanSPIE,
author = {Marrinan, Tim and Beveridge, J. Ross and Draper, Bruce and Kirby, Michael and Peterson, Chris},
booktitle = {SPIE Defense, Security, and Sensing},
title = {Flag-based detection of weak gas signatures in long-wave infrared hyperspectral image sequences.},
year = {2016},
doi = {10.1117/12.2224117},
}
[Abstract] 112
Accurate asymptotic analysis for johns test in multichannel signal detection
(Y-.H. Xiao, L. Huang, J. Xie and and H. C. So)
In Proc. IEEE Int. Conf. Acoust., Speech, Signal Process. (ICASSP), pp. 4358–4362, Shanghai, China, Mar. 2016. [BibTeX]
@inproceedings{Xiao2016ICASSP,
address = {Shanghai, China},
author = {Y-.H. Xiao and L. Huang and J. Xie and and H. C. So},
booktitle = {In Proc. IEEE Int. Conf. Acoust., Speech, Signal Process. (ICASSP)},
month = {Mar.},
title = {Accurate asymptotic analysis for johns test in multichannel signal detection},
year = {2016},
pages = {4358–4362},
}
[Abstract]
113
Bootstrap-based detection of the number of signals correlated across multiple data sets
(Tanuj Hasija, Yang Song, Peter J. Schreier and David Ramírez)
Proc. Asilomar Conf. Signals Syst. Computers, Pacific Grove, CA, USA, November 2016. [BibTeX]
@inproceedings{Hasija:2016ab,
address = {Pacific Grove, CA, USA},
author = {Hasija, Tanuj and Song, Yang and Schreier, Peter J. and Ram{\'i}rez, David},
booktitle = {{P}roc.\ {A}silomar {C}onf.\ {S}ignals\ {S}yst. {C}omputers},
month = {{N}ovember},
title = {Bootstrap-based detection of the number of signals correlated across multiple data sets},
year = {2016},
}
[Abstract]
114
Cross-validation techniques for determining the number of correlated components between two data sets when the number of samples is very small
(Christian Lameiro and Peter J. Schreier)
Proc. Asilomar Conf. Signals Syst. Computers, Pacific Grove, CA, USA, November 2016. [BibTeX]
@inproceedings{Lameiro:2016aa,
address = {Pacific Grove, CA, USA},
author = {Lameiro, Christian and Schreier, Peter J.},
booktitle = {{P}roc.\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {November},
title = {Cross-validation techniques for determining the number of correlated components between two data sets when the number of samples is very small},
year = {2016},
}
[Abstract]
115
Determining the number of signals correlated across multiple data sets for small sample support
(Yang Song, Tanuj Hasija, Peter J. Schreier and David Ramírez)
Proc. Eur. Signal Process. Conf., Budapest, Hungary, September 2016. [BibTeX]
@inproceedings{Song:2016ab,
address = {Budapest, Hungary},
author = {Song, Yang and Hasija, Tanuj and Schreier, Peter J. and Ram{\'i}rez, David},
booktitle = {{P}roc.\ {E}ur.\ {S}ignal {P}rocess.\ {C}onf.},
month = {{S}eptember},
title = {Determining the number of signals correlated across multiple data sets for small sample support},
year = {2016},
}
[Abstract]
116
Detecting the dimension of the subspace correlated across multiple data sets in the sample poor regime
(Tanuj Hasija, Yang Song, Peter J. Schreier and David Ramírez)
Proc. IEEE Work. Stat. Signal Process., Palma de Mallorca, Spain, June 2016. [BibTeX]
@inproceedings{Hasija:2016aa,
address = {Palma de Mallorca, Spain},
author = {Hasija, Tanuj and Song, Yang and Schreier, Peter J. and Ram{\'i}rez, David},
booktitle = {{P}roc.\ {IEEE} {W}ork.\ {S}tat.\ {S}ignal {P}rocess.},
month = {{J}une},
title = {Detecting the dimension of the subspace correlated across multiple data sets in the sample poor regime},
year = {2016},
}
[Abstract]
117
Analysis of the downlink saturation throughput of an asymmetric ieee 802.11 n-based wlan(
Mohammad Soleymani,
Behrouz Maham and Farid Ashtiani)
Proc. IEEE International Conference on Communications (ICC),
pp. 1–6,
Kuala Lumpur, Malaysia,
May 2016.DOI:10.1109/ICC.2016.7511453. [BibTeX]
@inproceedings{soleymani2016analysis,
address = {Kuala Lumpur, Malaysia},
author = {Soleymani, Mohammad and Maham, Behrouz and Ashtiani, Farid},
booktitle = {Proc. IEEE International Conference on Communications (ICC)},
month = {May},
title = {Analysis of the downlink saturation throughput of an asymmetric ieee 802.11 n-based wlan},
year = {2016},
pages = {1–6},
doi = {10.1109/ICC.2016.7511453},
}
[Abstract] 118
Measurement-driven quality assessment of nonlinear systems by exponential replacement
(Manuel Stein, Josef A. Nossek and Kurt Barbé)
Proc. IEEE Int. Instrum. & Meas. Tech. Conf., Taipei, Taiwan, May 2016. [BibTeX]
@inproceedings{Stein:I2MTC:2016,
address = {Taipei, Taiwan},
author = {Stein, Manuel and Nossek, Josef A. and Barb{\'e}, Kurt},
booktitle = {{P}roc.\ {IEEE} {I}nt. Instrum. \& Meas. Tech.\ {C}onf.},
month = {{M}ay},
title = {Measurement-driven quality assessment of nonlinear systems by exponential replacement},
year = {2016},
}
[Abstract]
119
Detection of cyclostationarity in the presence of temporal or spatial structure with applications to cognitive radio(
Aaron Pries,
David Ramírez and Peter J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 4249–4253,
Shanghai, China,
March 2016.DOI:10.1109/ICASSP.2016.7472478. [BibTeX]
@inproceedings{pries2016,
abstract = {One approach to spectrum sensing for cognitive radio is the detection of cyclostationarity. We extend an existing multi-antenna detector for cyclostationarity proposed by Ram{\'i}rez et al. [1], which makes no assumptions about the noise beyond being (temporally) wide-sense stationary. In special cases, the noise could be uncorrelated among antennas, or it could be temporally white. The performance of a general detector can be improved by making use of a priori structural information. We do not, however, require knowledge of the exact values of the temporal or spatial noise covariances. We develop an asymptotic generalized likelihood ratio test and evaluate the performance by simulations.},
address = {Shanghai, China},
author = {Aaron Pries and David Ram{\'i}rez and Peter J. Schreier},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Detection of cyclostationarity in the presence of temporal or spatial structure with applications to cognitive radio},
year = {2016},
pages = {4249–4253},
doi = {10.1109/ICASSP.2016.7472478},
}
[Abstract]
One approach to spectrum sensing for cognitive radio is the detection of cyclostationarity. We extend an existing multi-antenna detector for cyclostationarity proposed by Ramírez et al. [1], which makes no assumptions about the noise beyond being (temporally) wide-sense stationary. In special cases, the noise could be uncorrelated among antennas, or it could be temporally white. The performance of a general detector can be improved by making use of a priori structural information. We do not, however, require knowledge of the exact values of the temporal or spatial noise covariances. We develop an asymptotic generalized likelihood ratio test and evaluate the performance by simulations. 120
Maximally improper interference in underlay cognitive radio networks
(Christian Lameiro, I. Santamaría, W. Utschick and Peter J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Shanghai, China, March 2016. [BibTeX]
@inproceedings{Lameiro:2016aa,
address = {Shanghai, China},
author = {Lameiro, Christian and Santamar{\'i}a, I. and Utschick, W. and Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Maximally improper interference in underlay cognitive radio networks},
year = {2016},
}
[Abstract]
121
DOA parameter estimation with 1-bit quantization - Bounds, methods and the exponential replacement
(Manuel Stein, Kurt Barbé and Josef A. Nossek)
Proc. ITG Int. Work. Smart Ant., Munich, Germany, March 2016. [BibTeX]
@inproceedings{Stein:WSA:2016,
address = {Munich, Germany},
author = {Stein, Manuel and Barb{\'e}, Kurt and Nossek, Josef A.},
booktitle = {{P}roc.\ {ITG} {I}nt.\ {W}ork.\ Smart Ant.},
month = {{M}arch},
title = {{DOA} parameter estimation with 1-bit quantization - {B}ounds, methods and the exponential replacement},
year = {2016},
}
[Abstract]
122
Choosing the diagonal loading factor for linear signal estimation using cross validation
(Jun Tong, Qinghua Guo, Jiangtao Xi, Y. Yu and Peter J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Shanghai, China, March 2016. [BibTeX]
@inproceedings{Tong:2016ab,
address = {Shanghai, China},
author = {Tong, Jun and Guo, Qinghua and Xi, Jiangtao and Yu, Y. and Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Choosing the diagonal loading factor for linear signal estimation using cross validation},
year = {2016},
}
[Abstract]
123
Performance analysis for pilot-based 1-bit channel estimation with unknown quantization threshold
(Manuel Stein, Shahar Bar, Josef A. Nossek and Joseph Tabrikian)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Shanghai, China, February 2016. [BibTeX]
@inproceedings{Stein:ICASSP:2016:01,
address = {Shanghai, China},
author = {Stein, Manuel and Bar, Shahar and Nossek, Josef A. and Tabrikian, Joseph},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{F}ebruary},
title = {Performance analysis for pilot-based $1$-bit channel estimation with unknown quantization threshold},
year = {2016},
}
[Abstract]
124
Asymptotic performance analysis for 1-bit Bayesian smoothing
(Lin Zhang, Manuel Stein and Josef A. Nossek)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Shanghai, China, February 2016. [BibTeX]
@inproceedings{Zhang:ICASSP:2016,
address = {Shanghai, China},
author = {Zhang, Lin and Stein, Manuel and Nossek, Josef A.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{F}ebruary},
title = {Asymptotic performance analysis for $1$-bit {B}ayesian smoothing},
year = {2016},
}
[Abstract]
125
A simple DoF-achievable scheme for the Gaussian interference channel with delayed CSIT
(M. Rezaee, P. J. Schreier, M. Guillaud and B. Clerckx)
Proc. IEEE Global Communications Convference: Communication Theory, San Diego, CA, December 2015. [BibTeX]
@inproceedings{RezaeeSchreierGuillaud:2015:A-simple-DoF-achievable-scheme-for-the-Gaussian,
address = {San Diego, CA},
author = {M. Rezaee and P. J. Schreier and M. Guillaud and B. Clerckx},
booktitle = {Proc. IEEE Global Communications Convference: Communication Theory},
month = {{D}ecember},
title = {A simple {DoF}-achievable scheme for the {Gaussian} interference channel with delayed {CSIT}},
year = {2015},
}
[Abstract]
126
Flag manifolds for the characterization of geometric structure in large data sets(
Tim Marrinan,
J. Ross Beveridge,
Bruce Draper,
Michael Kirby and Chris Peterson)
Numerical Mathematics and Advanced Applications-ENUMATH 2013,
pp. 457–465,
Springer,
2015.DOI:10.1007/978-3-319-10705-9_45. [BibTeX]
@inproceedings{marrinanENUMATH,
author = {Marrinan, Tim and Beveridge, J. Ross and Draper, Bruce and Kirby, Michael and Peterson, Chris},
booktitle = {Numerical Mathematics and Advanced Applications-ENUMATH 2013},
title = {Flag manifolds for the characterization of geometric structure in large data sets},
year = {2015},
pages = {457–465},
doi = {10.1007/978-3-319-10705-9_45},
publisher = {Springer},
}
[Abstract] 127
Signal parameter estimation performance under a sampling rate constraint
(Andreas Lenz, Manuel Stein and Josef A. Nossek)
Asilomar Conf. Signals Syst. Computers, Pacific Grove, USA, November 2015. [BibTeX]
@inproceedings{Lenz:ASILO:2015,
address = {Pacific Grove, USA},
author = {Lenz, Andreas and Stein, Manuel and Nossek, Josef A.},
booktitle = {{A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Signal parameter estimation performance under a sampling rate constraint},
year = {2015},
}
[Abstract]
128
An experimental evaluation of broadband spatial IA for uncoordinated MIMO-OFDM systems(
Jacobo Fanjul,
Christian Lameiro,
Ignacio Santamaría,
Jose A. García-Naya and Luis Castedo)
Proc. IEEE Int. Conf. Digital Signal Process.,
Singapore,
July 2015. [BibTeX]
@inproceedings{FanjulLameiroSantamaria:2015:An-Experimental-Evaluation-of-Broadband-Spatial,
abstract = {In this paper we present an experimental study on the performance of spatial Interference Alignment (IA) in broadband indoor wireless local area network scenarios that use Orthogonal Frequency Division Multiplexing (OFDM) according to the IEEE 802.11a physical-layer specifications. Experiments have been carried out using a wireless network testbed made up of six nodes equipped with Multiple-Input Multiple-Output (MIMO) radio interfaces. This setup allows the implementation of a 3-user MIMO interference channel. We have implemented different IA decoding schemes that operate either before or after the Fast Fourier Transform block. IA has been experimentally evaluated comparing both approaches to analyze its performance in synchronous and asynchronous transmissions. Our results indicate that spatial IA performs satisfactorily in practical broadband indoor scenarios in which wireless channels often exhibit relatively large coherence times.},
address = {Singapore},
author = {Fanjul, Jacobo and Lameiro, Christian and Santamar{\'i}a, Ignacio and Garc{\'i}a-Naya, Jose A. and Castedo, Luis},
booktitle = {Proc. IEEE Int. Conf. Digital Signal Process.},
month = {July},
title = {An experimental evaluation of broadband spatial {IA} for uncoordinated {MIMO-OFDM} systems},
year = {2015},
}
[Abstract]
In this paper we present an experimental study on the performance of spatial Interference Alignment (IA) in broadband indoor wireless local area network scenarios that use Orthogonal Frequency Division Multiplexing (OFDM) according to the IEEE 802.11a physical-layer specifications. Experiments have been carried out using a wireless network testbed made up of six nodes equipped with Multiple-Input Multiple-Output (MIMO) radio interfaces. This setup allows the implementation of a 3-user MIMO interference channel. We have implemented different IA decoding schemes that operate either before or after the Fast Fourier Transform block. IA has been experimentally evaluated comparing both approaches to analyze its performance in synchronous and asynchronous transmissions. Our results indicate that spatial IA performs satisfactorily in practical broadband indoor scenarios in which wireless channels often exhibit relatively large coherence times. 129
Analysis of maximally improper signalling schemes for underlay cognitive radio(
Christian Lameiro,
Ignacio Santamaría and Peter J. Schreier)
Proc. IEEE Int. Conf. Comm.,
London, UK,
June 2015. [BibTeX]
@inproceedings{LameiroSantamariaSchreier:2015:Analysis-of-maximally-improper-signalling,
abstract = {In this paper, the impact of improper Gaussian signaling is studied for an underlay cognitive radio (CR) scenario comprised of a primary user (PU), which has a rate constraint, and a secondary user (SU), both single-antenna. We first derive expressions for the achievable rate of the SU when it transmits proper and maximally improper Gaussian signals (assuming that the SU is solely limited by the CR constraint). These expressions depend on the channel gains to and from the SU through a single variable. Thereby, we observe that improper signaling is beneficial whenever the SU rate is below a threshold, which depends on the signal-to-noise ratio (SNR) and rate requirement of the PU. Furthermore, we provide bounds on the achievable gain that also depend only on the PU parameters. Then, the achievable rate is studied from a statistical viewpoint by deriving its cumulative distribution function considering a constant received SNR at the PU. In addition, we specialize this expression for the Z interference channel, for which the expected achievable rate is also derived. Numerical examples illustrate our claims and show that the SU may significantly benefit from using improper signaling.},
address = {London, UK},
author = {Lameiro, Christian and Santamar{\'i}a, Ignacio and Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {C}omm.},
month = {{J}une},
title = {Analysis of maximally improper signalling schemes for underlay cognitive radio},
year = {2015},
}
[Abstract]
In this paper, the impact of improper Gaussian signaling is studied for an underlay cognitive radio (CR) scenario comprised of a primary user (PU), which has a rate constraint, and a secondary user (SU), both single-antenna. We first derive expressions for the achievable rate of the SU when it transmits proper and maximally improper Gaussian signals (assuming that the SU is solely limited by the CR constraint). These expressions depend on the channel gains to and from the SU through a single variable. Thereby, we observe that improper signaling is beneficial whenever the SU rate is below a threshold, which depends on the signal-to-noise ratio (SNR) and rate requirement of the PU. Furthermore, we provide bounds on the achievable gain that also depend only on the PU parameters. Then, the achievable rate is studied from a statistical viewpoint by deriving its cumulative distribution function considering a constant received SNR at the PU. In addition, we specialize this expression for the Z interference channel, for which the expected achievable rate is also derived. Numerical examples illustrate our claims and show that the SU may significantly benefit from using improper signaling. 130
An asymptotic LMPI test for cyclostationarity detection with application to cognitive radio (invited paper)(
D. Ramírez,
P. J. Schreier,
J. Vía,
I. Santamaría and L. L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Brisbane, Australia,
April 2015. [BibTeX]
@inproceedings{RamirezSchreierVia:2015:An-asymptotic-LMPI-test-for-cyclostationarity,
abstract = {We propose a new detector of primary users in cognitive radio networks. The main novelty of the proposed detector in comparison to most known detectors is that it is based on sound statistical principles for detecting cyclostationary signals. In particular, the proposed detector is (asymptotically) the locally most powerful invariant test, i.e. the best invariant detector for low signal-to-noise ratios. The derivation is based on two main ideas: the relationship between a scalar-valued cyclostationary signal and a vector-valued wide-sense stationary signal, and Wijsman's theorem. Moreover, using the spectral representation for the cyclostationary time series, the detector has an insightful interpretation, and implementation, as the broadband coherence between frequencies that are separated by multiples of the cycle frequency. Finally, simulations confirm that the proposed detector performs better than previous approaches.},
address = {Brisbane, Australia},
author = {D. Ram{\'i}rez and P. J. Schreier and J. V{\'i}a and I. Santamar{\'i}a and L. L. Scharf},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {An asymptotic {LMPI} test for cyclostationarity detection with application to cognitive radio (invited paper)},
year = {2015},
}
[Abstract]
We propose a new detector of primary users in cognitive radio networks. The main novelty of the proposed detector in comparison to most known detectors is that it is based on sound statistical principles for detecting cyclostationary signals. In particular, the proposed detector is (asymptotically) the locally most powerful invariant test, i.e. the best invariant detector for low signal-to-noise ratios. The derivation is based on two main ideas: the relationship between a scalar-valued cyclostationary signal and a vector-valued wide-sense stationary signal, and Wijsman's theorem. Moreover, using the spectral representation for the cyclostationary time series, the detector has an insightful interpretation, and implementation, as the broadband coherence between frequencies that are separated by multiples of the cycle frequency. Finally, simulations confirm that the proposed detector performs better than previous approaches. 131
Model-order selection for analyzing correlation between two data sets using CCA with PCA preprocessing
(N. Roseveare and P. J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Brisbane, Australia, April 2015. [BibTeX]
@inproceedings{RoseveareSchreier:2015:Model-order-selection-for-analyzing-correlation,
address = {Brisbane, Australia},
author = {N. Roseveare and P. J. Schreier},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {Model-order selection for analyzing correlation between two data sets using {CCA} with {PCA} preprocessing},
year = {2015},
}
[Abstract]
132
Determining the number of correlated signals between two data sets using PCA-CCA when sample support is extremely small(
Y. Song,
P. J. Schreier and N. Roseveare)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Brisbane, Australia,
April 2015. [BibTeX]
@inproceedings{SongSchreierRoseveare:2015:Determining-the-number-of-correlated-signals,
address = {Brisbane, Australia},
author = {Y. Song and P. J. Schreier and N. Roseveare},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {Determining the number of correlated signals between two data sets using {PCA-CCA} when sample support is extremely small},
year = {2015},
}
[Abstract] 133
Ranging with high accuracy and without ambiguities
(Sebastian Theiler, Manuel Stein and Josef A. Nossek)
Proc. IEEE Work. Pos. Nav. & Com., Dresden, Germany, March 2015. [BibTeX]
@inproceedings{Theiler:WPNC:2015,
address = {Dresden, Germany},
author = {Theiler, Sebastian and Stein, Manuel and Nossek, Josef A.},
booktitle = {{P}roc.\ {IEEE} {W}ork. {P}os.\ {N}av. \& {C}om.},
month = {{M}arch},
title = {Ranging with high accuracy and without ambiguities},
year = {2015},
}
[Abstract]
134
Input-to-state stability for discrete-time monotone systems
(Björn S. Rüffer and Rudolf Sailer)
Proc. 21st Int. Symp. Mathematical Theory of Networks and Systems (MTNS), 2014. [BibTeX]
@inproceedings{ruffersailer2014-input-to-state-stability-for-discrete-time-monotone-systems,
abstract = {It is well known that input-to-state stability admits an astonishing number of equivalent characterizations. Here it is shown that for monotone systems on $\Rnp$ there are some additional characterizations that are useful for network stability analysis. These characterizations include system theoretic properties, algebraic properties, as well as the problem of finding simultaneous bounds on solutions to a collection of inequalities.},
author = {Bj{\"o}rn S. R{\"u}ffer and Rudolf Sailer},
booktitle = {Proc. 21st Int. Symp. Mathematical Theory of Networks and Systems (MTNS)},
title = {Input-to-state stability for discrete-time monotone systems},
year = {2014},
}
[Abstract]
It is well known that input-to-state stability admits an astonishing number of equivalent characterizations. Here it is shown that for monotone systems on Rnp there are some additional characterizations that are useful for network stability analysis. These characterizations include system theoretic properties, algebraic properties, as well as the problem of finding simultaneous bounds on solutions to a collection of inequalities.
135
Finding the subspace mean or median to fit your need(
Tim Marrinan,
Bruce Draper,
J. Ross Beveridge,
Michael Kirby and Chris Peterson)
CVPR,
pp. 1082–1089,
2014.DOI:10.1109/CVPR.2014.142. [BibTeX]
@inproceedings{marrinanCVPR,
author = {Marrinan, Tim and Draper, Bruce and Beveridge, J. Ross and Kirby, Michael and Peterson, Chris},
booktitle = {CVPR},
title = {Finding the subspace mean or median to fit your need},
year = {2014},
pages = {1082–1089},
doi = {10.1109/CVPR.2014.142},
}
[Abstract] 136
A regularized maximum likelihood estimator for the period of a cyclostationary process(
D. Ramírez,
P. J. Schreier,
J. Vía,
I. Santamaría and L. L. Scharf)
Proc. Asilomar Conf. Signals Syst. Computers,
Pacific Grove, USA,
November 2014. [BibTeX]
@inproceedings{RamirezSchreierVia:2014:A-Regularized-Maximum-Likelihood-Estimator,
abstract = {We derive an estimator of the cycle period of a univariate cyclostationary process based on an information- theoretic criterion. Transforming the univariate cyclostationary process into a vector-valued wide-sense stationary process allows us to obtain the structure of the covariance matrix, which is block-Toeplitz, and its block size depends on the unknown cycle period. Therefore, we sweep the block size and obtain the ML estimate of the covariance matrix, required for the information- theoretic criterion. Since there are no closed-form ML estimates of block-Toeplitz matrices, we asymptotically approximate them as block-circulant. Finally, some numerical examples show the good performance of the proposed estimator.},
address = {Pacific Grove, USA},
author = {D. Ram{\'i}rez and P. J. Schreier and J. V{\'i}a and I. Santamar{\'i}a and L. L. Scharf},
booktitle = {{P}roc.\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {A regularized maximum likelihood estimator for the period of a cyclostationary process},
year = {2014},
}
[Abstract]
We derive an estimator of the cycle period of a univariate cyclostationary process based on an information- theoretic criterion. Transforming the univariate cyclostationary process into a vector-valued wide-sense stationary process allows us to obtain the structure of the covariance matrix, which is block-Toeplitz, and its block size depends on the unknown cycle period. Therefore, we sweep the block size and obtain the ML estimate of the covariance matrix, required for the information- theoretic criterion. Since there are no closed-form ML estimates of block-Toeplitz matrices, we asymptotically approximate them as block-circulant. Finally, some numerical examples show the good performance of the proposed estimator. 137
Interference-temperature limit for cognitive radio networks with MIMO primary users(
Christian Lameiro,
Wolfgang Utschick and Ignacio Santamaría)
Proc. Asilomar Conf. Signals Syst. Computers,
Pacific Grove, CA, USA,
November 2014.DOI:10.1109/ACSSC.2014.7094625. [BibTeX]
@inproceedings{LameiroUtschickSantamaria:2014:Interference-Temperature-Limit-for-Cognitive-Radio,
abstract = {This paper derives the interference-temperature (IT) limit for a multi-antenna primary user (PU) with a rate constraint. While in the case of a single-antenna PU there is a one-to-one mapping between IT and achievable rate, this correspondence does not hold anymore when a multiple-input multiple-output (MIMO) system is considered. In such cases, the spatial distribution of the interference must be taken into account, since it strongly affects the PU performance. To this end, we derive a closed-form expression for the maximum IT that can be tolerated by identifying the worst-case interference covariance matrix, which results in a multilevel waterfilling problem.},
address = {Pacific Grove, CA, USA},
author = {Lameiro, Christian and Utschick, Wolfgang and Santamar{\'i}a, Ignacio},
booktitle = {{P}roc.\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Interference-temperature limit for cognitive radio networks with {MIMO} primary users},
year = {2014},
doi = {10.1109/ACSSC.2014.7094625},
}
[Abstract]
This paper derives the interference-temperature (IT) limit for a multi-antenna primary user (PU) with a rate constraint. While in the case of a single-antenna PU there is a one-to-one mapping between IT and achievable rate, this correspondence does not hold anymore when a multiple-input multiple-output (MIMO) system is considered. In such cases, the spatial distribution of the interference must be taken into account, since it strongly affects the PU performance. To this end, we derive a closed-form expression for the maximum IT that can be tolerated by identifying the worst-case interference covariance matrix, which results in a multilevel waterfilling problem. 138
Optimizing spatial filters for the extraction of envelope-coupled neural oscillations(
S. Dähne,
V. V. Nikulin,
D. Ramírez,
P. J. Schreier,
K.-R. Müller and S. Haufe)
Proc. Int. Work. Pattern Recognition In Neuroimaging,
Tübingen, Germany,
June 2014.DOI:10.1109/PRNI.2014.6858514. [BibTeX]
@inproceedings{DahneNikulinRamirez:2014:Optimizing-spatial-filters-for-the-extraction,
abstract = {Amplitude-to-amplitude interactions between neural oscillations are of a special interest as they show how the strength of spatial synchronization in different neuronal populations relates to each other during a given task. While, previously, amplitude-to-amplitude correlations were studied primarily on the sensor level, we present a source separation approach using spatial filters which maximize the correlation between the envelopes of brain oscillations recorded with electro-/magnetencephalography (EEG/MEG) or intracranial multichannel recordings. Our approach, which is called canonical source power correlation analysis (cSPoC), is thereby capable of extracting genuine brain oscillations solely based on their assumed coupling behavior even when the signal-to-noise ratio of the signals is low.},
address = {T{\"u}bingen, Germany},
author = {S. D{\"a}hne and V. V. Nikulin and D. Ram{\'i}rez and P. J. Schreier and K.-R. M{\"u}ller and S. Haufe},
booktitle = {Proc.\ Int. Work. Pattern Recognition In Neuroimaging},
month = {{J}une},
title = {Optimizing spatial filters for the extraction of envelope-coupled neural oscillations},
year = {2014},
doi = {10.1109/PRNI.2014.6858514},
}
[Abstract]
Amplitude-to-amplitude interactions between neural oscillations are of a special interest as they show how the strength of spatial synchronization in different neuronal populations relates to each other during a given task. While, previously, amplitude-to-amplitude correlations were studied primarily on the sensor level, we present a source separation approach using spatial filters which maximize the correlation between the envelopes of brain oscillations recorded with electro-/magnetencephalography (EEG/MEG) or intracranial multichannel recordings. Our approach, which is called canonical source power correlation analysis (cSPoC), is thereby capable of extracting genuine brain oscillations solely based on their assumed coupling behavior even when the signal-to-noise ratio of the signals is low. 139
Regularized successive interference cancellation (sic) under mismatched modeling(
Jun Tong,
Qinghua Guo,
Peter J. Schreier and Jiangtao Xi)
Proc. IEEE Work. Stat. Signal Process.,
Gold Coast, Australia,
June 2014.DOI:10.1109/SSP.2014.6884642. [BibTeX]
@inproceedings{TongGuoSchreier:2014:Regularized-successive-interference-cancellation,
abstract = {Successive interference cancellation (SIC) has been extensively applied to estimate transmit signals in communication systems. When the channel state information (CSI) and noise statistics are imperfectly estimated, the standard SIC estimators that ignore the model mismatch may perform poorly. This paper introduces regularized SIC estimation to provide robustness against the model mismatch. Suboptimal, low-complexity implementations using (sorted) QR decomposition and approximate choice of regularization parameters are also introduced. Simulation examples demonstrate that the regularized SIC estimators can significantly outperform the standard version.},
address = {Gold Coast, Australia},
author = {Tong, Jun and Guo, Qinghua and Schreier, Peter J. and Xi, Jiangtao},
booktitle = {{P}roc.\ {IEEE} {W}ork.\ {S}tat.\ {S}ignal {P}rocess.},
month = {{J}une},
title = {Regularized successive interference cancellation (sic) under mismatched modeling},
year = {2014},
doi = {10.1109/SSP.2014.6884642},
}
[Abstract]
Successive interference cancellation (SIC) has been extensively applied to estimate transmit signals in communication systems. When the channel state information (CSI) and noise statistics are imperfectly estimated, the standard SIC estimators that ignore the model mismatch may perform poorly. This paper introduces regularized SIC estimation to provide robustness against the model mismatch. Suboptimal, low-complexity implementations using (sorted) QR decomposition and approximate choice of regularization parameters are also introduced. Simulation examples demonstrate that the regularized SIC estimators can significantly outperform the standard version. 140
An asymptotic GLRT for the detection of cyclostationary signals(
D. Ramírez,
L. L. Scharf,
J. Vía,
I. Santamaría and P. J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Florence, Italy,
May 2014.DOI:10.1109/ICASSP.2014.6854234. [BibTeX]
@inproceedings{RamirezScharfVia:2014:An-asymptotic-GLRT-for-the-detection-of-cyclostationary,
abstract = {We derive the generalized likelihood ratio test (GLRT) for detecting cyclostationarity in scalar-valued time series. The main idea behind our approach is Gladyshev's relationship, which states that when the scalar-valued cyclostationary sig- nal is blocked at the known cycle period it produces a vector- valued wide-sense stationary process. This result amounts to saying that the covariance matrix of the vector obtained by stacking all observations of the time series is block-Toeplitz if the signal is cyclostationary, and Toeplitz if the signal is wide- sense stationary. The derivation of the GLRT requires the maximum likelihood estimates of Toeplitz and block-Toeplitz matrices. This can be managed asymptotically (for large num- berofsamples)exploitingSzego ̈'stheoremanditsgeneraliza- tion for vector-valued processes. Simulation results show the good performance of the proposed GLRT.},
address = {Florence, Italy},
author = {D. Ram{\'i}rez and L. L. Scharf and J. V{\'i}a and I. Santamar{\'i}a and P. J. Schreier},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {An asymptotic {GLRT} for the detection of cyclostationary signals},
year = {2014},
doi = {10.1109/ICASSP.2014.6854234},
}
[Abstract]
We derive the generalized likelihood ratio test (GLRT) for detecting cyclostationarity in scalar-valued time series. The main idea behind our approach is Gladyshev's relationship, which states that when the scalar-valued cyclostationary sig- nal is blocked at the known cycle period it produces a vector- valued wide-sense stationary process. This result amounts to saying that the covariance matrix of the vector obtained by stacking all observations of the time series is block-Toeplitz if the signal is cyclostationary, and Toeplitz if the signal is wide- sense stationary. The derivation of the GLRT requires the maximum likelihood estimates of Toeplitz and block-Toeplitz matrices. This can be managed asymptotically (for large num- berofsamples)exploitingSzego ̈'stheoremanditsgeneraliza- tion for vector-valued processes. Simulation results show the good performance of the proposed GLRT. 141
Interference shaping constraints for underlay MIMO interference channels(
Christian Lameiro,
Ignacio Santamaría and Wolfgang Utschick)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Florence, Italy,
May 2014.DOI:10.1109/ICASSP.2014.6855020. [BibTeX]
@inproceedings{LameiroSantamariaUtschick:2014:Interference-Shaping-Constraints-for-Underlay,
abstract = {In this paper, a cognitive radio (CR) scenario comprised of a secondary interference channel (IC) and a primary point-to-point link (PPL) is studied, when the former interferes the latter. In order to satisfy a given rate requirement at the PPL, typical approaches impose an interference temperature constraint (IT). When the PPL transmits multiple streams, however, the spatial structure of the interference comes into play. In such cases, we show that spatial interference shaping constraints can provide higher sum-rate performance to the IC while ensuring the required rate at the PPL. Then, we extend the interference leakage minimization algorithm (MinIL) to incorporate such constraints. An additional power control step is included in the optimization procedure to improve the sum-rate when the interference alignment (IA) problem becomes infeasible due to the additional constraint. Numerical examples are provided to illustrate the effectiveness of the spatial shaping constraint in comparison to IT when the PPL transmits multiple data streams.},
address = {Florence, Italy},
author = {Lameiro, Christian and Santamar{\'i}a, Ignacio and Utschick, Wolfgang},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Interference shaping constraints for underlay {MIMO} interference channels},
year = {2014},
doi = {10.1109/ICASSP.2014.6855020},
}
[Abstract]
In this paper, a cognitive radio (CR) scenario comprised of a secondary interference channel (IC) and a primary point-to-point link (PPL) is studied, when the former interferes the latter. In order to satisfy a given rate requirement at the PPL, typical approaches impose an interference temperature constraint (IT). When the PPL transmits multiple streams, however, the spatial structure of the interference comes into play. In such cases, we show that spatial interference shaping constraints can provide higher sum-rate performance to the IC while ensuring the required rate at the PPL. Then, we extend the interference leakage minimization algorithm (MinIL) to incorporate such constraints. An additional power control step is included in the optimization procedure to improve the sum-rate when the interference alignment (IA) problem becomes infeasible due to the additional constraint. Numerical examples are provided to illustrate the effectiveness of the spatial shaping constraint in comparison to IT when the PPL transmits multiple data streams. 142
Optimum analog receive filters for detection and inference under a sampling rate constraint
(Manuel Stein, Andreas Lenz, Amine Mezghani and Josef A. Nossek)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Florence, Italy, May 2014. [BibTeX]
@inproceedings{Stein:ICASSP:2014,
address = {Florence, Italy},
author = {Stein, Manuel and Lenz, Andreas and Mezghani, Amine and Nossek, Josef A.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Optimum analog receive filters for detection and inference under a sampling rate constraint},
year = {2014},
}
[Abstract]
143
Spatial shaping and precoding design for underlay MIMO interference channels(
Christian Lameiro,
Wolfgang Utschick and Ignacio Santamaría)
Proc.Int. ITG Work. Smart Antennas,
Erlangen, Germany,
March 2014. [BibTeX]
@inproceedings{LameiroUtschickSantamaria:2014:Spatial-Shaping-and-Precoding-Design,
abstract = {In this paper, we study coexistence issues between an underlay single-beam interference channel (IC) and a primary point-to-point link (PPL) that has a rate constraint. We derive spatial shaping constraints at the secondary transmitters and show that they generalize the so-called interference temperature (IT) when the PPL transmits multiple streams. We propose a successive convex approximation algorithm to compute the spatial shaping matrices that maximize the allowed transmit power of the IC while ensuring the rate constraint of the PPL. Then, we provide general interference leakage minimization (MinIL) and maximum signal-to-interference-plus-noise ratio (MaxSINR) algorithms that can incorporate both types of constraint. An additional power control step is included in the optimization procedure to further improve the sum-rate of the IC. Different numerical examples are provided to illustrate the effectiveness of the proposed techniques and to compare the performance improvement when the IC is subject to spatial shaping constraints in comparison to IT.},
address = {Erlangen, Germany},
author = {Lameiro, Christian and Utschick, Wolfgang and Santamar{\'i}a, Ignacio},
booktitle = {Proc.Int. ITG Work. Smart Antennas},
month = {{M}arch},
title = {Spatial shaping and precoding design for underlay {MIMO} interference channels},
year = {2014},
}
[Abstract]
In this paper, we study coexistence issues between an underlay single-beam interference channel (IC) and a primary point-to-point link (PPL) that has a rate constraint. We derive spatial shaping constraints at the secondary transmitters and show that they generalize the so-called interference temperature (IT) when the PPL transmits multiple streams. We propose a successive convex approximation algorithm to compute the spatial shaping matrices that maximize the allowed transmit power of the IC while ensuring the rate constraint of the PPL. Then, we provide general interference leakage minimization (MinIL) and maximum signal-to-interference-plus-noise ratio (MaxSINR) algorithms that can incorporate both types of constraint. An additional power control step is included in the optimization procedure to further improve the sum-rate of the IC. Different numerical examples are provided to illustrate the effectiveness of the proposed techniques and to compare the performance improvement when the IC is subject to spatial shaping constraints in comparison to IT. 144
Information-preserving spatial filtering for direction-of-arrival estimation
(Manuel Stein, Mario Castañeda and Josef A. Nossek)
Proc. ITG Int. Work. Smart Ant., Erlangen, Germany, March 2014. [BibTeX]
@inproceedings{Stein:WSA:2014,
address = {Erlangen, Germany},
author = {Stein, Manuel and Casta{\~n}eda, Mario and Nossek, Josef A.},
booktitle = {{P}roc.\ {ITG} {I}nt.\ {W}ork.\ Smart Ant.},
month = {{M}arch},
title = {Information-preserving spatial filtering for direction-of-arrival estimation},
year = {2014},
}
[Abstract]
145
Will the 1-bit GNSS receiver prevail?
(Manuel Stein and Josef A. Nossek)
Proc. IEEE/ION Pos. Nav. Symp., Monterey, USA, March 2014. [BibTeX]
@inproceedings{Stein:PLANS:2014,
address = {Monterey, USA},
author = {Stein, Manuel and Nossek, Josef A.},
booktitle = {{P}roc.\ {IEEE}{\/}{ION} {P}os. {N}av.\ Symp.},
month = {{M}arch},
title = {Will the 1-bit {GNSS} receiver prevail?},
year = {2014},
}
[Abstract]
146
Input-dependent stability analysis of systems with saturation in feedback
(Alexander Yu. Pogromsky, Alexey S. Matveev, Antoine Chaillet and Björn S. Rüffer)
Proc. 52nd IEEE Conf. Decis. Control, pp. 5903–5908, 2013. [BibTeX]
@inproceedings{pogromskymatveevchailletruffer2013-input-dependent-stability-analysis-of-systems-with-saturation-in-feedback,
abstract = {The paper deals with global stability analysis of linear control systems with saturation in feedback driven by an external input. Various new criteria based on non-quadratic Lyapunov functions are proposed, that unlike many previous results, offer better account for the role of the external excitation by providing input-dependent conditions for stability of solutions. For example, it is shown that even if the system fails to satisfy the incremental version of the circle criterion, the stability is guaranteed whenever the uniform root mean square value of the input signal is less than a computable threshold. The general theoretical results are illustrated in the case of the double integrator closed by a saturated linear feedback with an external excitation.},
author = {Alexander {Yu.} Pogromsky and Alexey S. Matveev and Antoine Chaillet and Bj{\"o}rn S. R{\"u}ffer},
booktitle = {{P}roc. 52nd {IEEE} {C}onf. {D}ecis. {C}ontrol},
title = {Input-dependent stability analysis of systems with saturation in feedback},
year = {2013},
pages = {5903–5908},
}
[Abstract]
The paper deals with global stability analysis of linear control systems with saturation in feedback driven by an external input. Various new criteria based on non-quadratic Lyapunov functions are proposed, that unlike many previous results, offer better account for the role of the external excitation by providing input-dependent conditions for stability of solutions. For example, it is shown that even if the system fails to satisfy the incremental version of the circle criterion, the stability is guaranteed whenever the uniform root mean square value of the input signal is less than a computable threshold. The general theoretical results are illustrated in the case of the double integrator closed by a saturated linear feedback with an external excitation.
147
Separable Lyapunov functions for monotone systems
(Anders Rantzer, Björn S. Rüffer and Gunther Dirr)
Proc. 52nd IEEE Conf. Decis. Control, pp. 4590–4594, 2013. [BibTeX]
@inproceedings{rantzerrufferdirr2013-separable-lyapunov-functions-for-monotone-systems,
abstract = {Separable Lyapunov functions play vital roles, for example, in stability analysis of large-scale systems. A Lyapunov function is called max-separable if it can be decomposed into a maximum of functions with one-dimensional arguments. Similarly, it is called sum-separable if it is a sum of such functions. In this paper it is shown that for a monotone system on a compact state space, asymptotic stability implies existence of a max-separable Lyapunov function. We also construct two systems on a non-compact state space, for which a max-separable Lyapunov function does not exist. One of them has a sum-separable Lyapunov function. The other does not.},
author = {Anders Rantzer and Bj{\"o}rn S. R{\"u}ffer and Gunther Dirr},
booktitle = {{P}roc. 52nd {IEEE} {C}onf. {D}ecis. {C}ontrol},
title = {Separable {L}yapunov functions for monotone systems},
year = {2013},
pages = {4590–4594},
}
[Abstract]
Separable Lyapunov functions play vital roles, for example, in stability analysis of large-scale systems. A Lyapunov function is called max-separable if it can be decomposed into a maximum of functions with one-dimensional arguments. Similarly, it is called sum-separable if it is a sum of such functions. In this paper it is shown that for a monotone system on a compact state space, asymptotic stability implies existence of a max-separable Lyapunov function. We also construct two systems on a non-compact state space, for which a max-separable Lyapunov function does not exist. One of them has a sum-separable Lyapunov function. The other does not.
148
A Razumikhin approach for the incremental stability of delayed nonlinear systems
(Antoine Chaillet, Alexander Yu. Pogromsky and Björn S. Rüffer)
Proc. 52nd IEEE Conf. Decis. Control, pp. 1596–1601, 2013. [BibTeX]
@inproceedings{chailletpogromskyruffer2013-a-razumikhin-approach-for-the-incremental-stability-of-delayed-nonlinear-systems,
abstract = {This paper provides sufficient conditions for the incremental stability of time-delayed nonlinear systems. It relies on the Razumikhin-Lyapunov approach, which consists in invoking small-gain arguments by treating the delayed state as a feedback perturbation. The results are valid for multiple delays, as well as bounded time-varying delays. We provide conditions under which the limit solution of a time-delayed nonlinear system to a periodic (resp. constant) input is itself periodic and of the same period (resp. constant). As an illustration, a specific focus is given on a class of delayed Lur'e systems.},
author = {Antoine Chaillet and Alexander {Yu.} Pogromsky and Bj{\"o}rn S. R{\"u}ffer},
booktitle = {{P}roc. 52nd {IEEE} {C}onf. {D}ecis. {C}ontrol},
title = {A {R}azumikhin approach for the incremental stability of delayed nonlinear systems},
year = {2013},
pages = {1596–1601},
}
[Abstract]
This paper provides sufficient conditions for the incremental stability of time-delayed nonlinear systems. It relies on the Razumikhin-Lyapunov approach, which consists in invoking small-gain arguments by treating the delayed state as a feedback perturbation. The results are valid for multiple delays, as well as bounded time-varying delays. We provide conditions under which the limit solution of a time-delayed nonlinear system to a periodic (resp. constant) input is itself periodic and of the same period (resp. constant). As an illustration, a specific focus is given on a class of delayed Lur'e systems.
149
A two-phase approach to stability of networks given in iISS framework: utilization of a matrix-like criterion
(Hiroshi Ito and Björn S. Rüffer)
Proc. IEEE American Contr. Conf., pp. 4838–4843, 2013. [BibTeX]
@inproceedings{itoruffer2013-a-two-phase-approach-to-stability-of-networks-given-in-iiss-framework:-utilization-of-a-matrix-like-criterion,
abstract = {This article is concerned with global asymptotic stability (GAS) of dynamical networks. The case when subsystems are integral input-to-state stable (iISS) has been recognized as notoriously difficult to deal with in the literature. In fact, the lack of energy dissipation for large input denies direct application of the small-gain argument for input-to-state stable (ISS) subsystems. Here for networks consisting of iISS subsystems it is demonstrated that a two-phase approach allows us to make use of the ISS small-gain argument by separating a trajectory into a transient and a subsequent convergence. In contrast to the previous iISS results, the two-phase approach immediately leads to a sufficient criterion for GAS of general nonlinear networks in a matrix-like form (order condition).},
author = {Ito, Hiroshi and R{\"u}ffer, Bj{\"o}rn S.},
booktitle = {{P}roc. {IEEE} {A}merican {C}ontr. {C}onf.},
title = {A two-phase approach to stability of networks given in {iISS} framework: utilization of a matrix-like criterion},
year = {2013},
pages = {4838–4843},
}
[Abstract]
This article is concerned with global asymptotic stability (GAS) of dynamical networks. The case when subsystems are integral input-to-state stable (iISS) has been recognized as notoriously difficult to deal with in the literature. In fact, the lack of energy dissipation for large input denies direct application of the small-gain argument for input-to-state stable (ISS) subsystems. Here for networks consisting of iISS subsystems it is demonstrated that a two-phase approach allows us to make use of the ISS small-gain argument by separating a trajectory into a transient and a subsequent convergence. In contrast to the previous iISS results, the two-phase approach immediately leads to a sufficient criterion for GAS of general nonlinear networks in a matrix-like form (order condition).
150
Linear equalization in communications with mismatched modeling using Krylov subspace expansion
(Jun Tong and Peter J. Schreier)
Proc. IEEE Wireless Comm. Networking Conf. (WCNC), 2013. [BibTeX]
@inproceedings{TongSchreier:2013:Linear-equalization-in-comm,
author = {Tong, Jun and Schreier, Peter J.},
booktitle = {Proc. IEEE Wireless Comm. Networking Conf. (WCNC)},
title = {Linear equalization in communications with mismatched modeling using {K}rylov subspace expansion},
year = {2013},
}
[Abstract]
151
Joint space-time interference mitigation for embedded multi-antenna GNSS receivers
(Mario Castañeda, Manuel Stein, Felix Antreich, Emrah Tasdemir, Lothar Kurz, Tobias G. Noll and Josef A. Nossek)
ION GNSS+, Nashville, USA, September 2013. [BibTeX]
@inproceedings{Castaneda:ICASSP:2013,
address = {Nashville, USA},
author = {Casta{\~n}eda, Mario and Stein, Manuel and Antreich, Felix and Tasdemir, Emrah and Kurz, Lothar and Noll, Tobias G. and Nossek, Josef A.},
booktitle = {{ION} {G}NSS+},
month = {{S}eptember},
title = {Joint space-time interference mitigation for embedded multi-antenna {GNSS} receivers},
year = {2013},
}
[Abstract]
152
An interference alignment algorithm for structured channels(
Christian Lameiro,
Óscar González and Ignacio Santamaría)
Proc. IEEE Work. Signal Process. Advances in Wireless Comm.,
Darmstadt, Germany,
June 2013.DOI:10.1109/SPAWC.2013.6612059. [BibTeX]
@inproceedings{LameiroGonzalezSantamaria:2013:An-Interference-Alignment-Algorithm-for-Structured,
abstract = {In this paper we propose a new interference alignment (IA) algorithm specifically designed to work with structured channels (e.g., diagonal or block-diagonal). Multiple-input multiple-output (MIMO) structured channels arise when symbol extensions -either in time or frequency- are employed jointly with the spatial dimension in the design of the precoders. In this case, the rank constraint in the direct channels must explicitly be taken into account into the optimization problem to ensure that there is no degrees-of-freedom (DoF) loss. To this end, we propose an algorithm that minimizes the interference leakage while ensuring that the direct links are full rank and the transmitters satisfy a power constraint. The algorithm is based upon an alternating optimization procedure, which solves a generalized eigenvalue problem at each step. We show through simulations the advantages of the proposed algorithm in several scenarios that use symbols extensions or improper (a.k.a. asymmetric) signalling.},
address = {Darmstadt, Germany},
author = {Lameiro, Christian and Gonz{\'a}lez, {\'O}scar and Santamar{\'i}a, Ignacio},
booktitle = {Proc. IEEE Work. Signal Process. Advances in Wireless Comm.},
month = {{J}une},
title = {An interference alignment algorithm for structured channels},
year = {2013},
doi = {10.1109/SPAWC.2013.6612059},
}
[Abstract]
In this paper we propose a new interference alignment (IA) algorithm specifically designed to work with structured channels (e.g., diagonal or block-diagonal). Multiple-input multiple-output (MIMO) structured channels arise when symbol extensions -either in time or frequency- are employed jointly with the spatial dimension in the design of the precoders. In this case, the rank constraint in the direct channels must explicitly be taken into account into the optimization problem to ensure that there is no degrees-of-freedom (DoF) loss. To this end, we propose an algorithm that minimizes the interference leakage while ensuring that the direct links are full rank and the transmitters satisfy a power constraint. The algorithm is based upon an alternating optimization procedure, which solves a generalized eigenvalue problem at each step. We show through simulations the advantages of the proposed algorithm in several scenarios that use symbols extensions or improper (a.k.a. asymmetric) signalling. 153
Degrees-of-freedom for the 4-user SISO interference channel with improper signaling(
Christian Lameiro and Ignacio Santamaría)
Proc. IEEE Int. Conf. Comm.,
Budapest, Hungary,
June 2013.DOI:10.1109/ICC.2013.6655009. [BibTeX]
@inproceedings{LameiroSantamaria:2013:Degrees-of-Freedom-for-the-4-User-SISO-Interference,
abstract = {It has been recently shown that for the 3-user single-input single-output (SISO) interference channel with constant channel coefficients, a maximum of 1.2 degrees-of-freedom (DoF) are achievable using linear interference alignment schemes when improper (a.k.a. asymmetric) Gaussian signaling is applied. In this paper, we study the 4-user SISO interference channel and provide inner and outer bounds for the total number of DoF achievable for this channel. We prove that at least 4/3 DoF are achievable for the 4-user channel using also linear interference alignment techniques and improper signaling. A simple converse proof shows that no more than 8/5 DoF are achievable for this scheme. Simulation results seem to indicate that the inner bound is in fact tight for this channel, and serve to illustrate the sum-rate improvement with respect to time division multiple access (TDMA) techniques.},
address = {Budapest, Hungary},
author = {Lameiro, Christian and Santamar{\'i}a, Ignacio},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {C}omm.},
month = {{J}une},
title = {Degrees-of-freedom for the 4-user {SISO} interference channel with improper signaling},
year = {2013},
doi = {10.1109/ICC.2013.6655009},
}
[Abstract]
It has been recently shown that for the 3-user single-input single-output (SISO) interference channel with constant channel coefficients, a maximum of 1.2 degrees-of-freedom (DoF) are achievable using linear interference alignment schemes when improper (a.k.a. asymmetric) Gaussian signaling is applied. In this paper, we study the 4-user SISO interference channel and provide inner and outer bounds for the total number of DoF achievable for this channel. We prove that at least 4/3 DoF are achievable for the 4-user channel using also linear interference alignment techniques and improper signaling. A simple converse proof shows that no more than 8/5 DoF are achievable for this scheme. Simulation results seem to indicate that the inner bound is in fact tight for this channel, and serve to illustrate the sum-rate improvement with respect to time division multiple access (TDMA) techniques. 154
Principal component analysis to extract blood oxygenation from theoretical modeling of total diffuse reflectance spectra
(Alma Eguizabal, Pilar Garcia-Allende, Karin Jentoft, Panagiotis Symvoulidis, Jose Lopez-Higuera, Vasilis Ntziachristos and Olga M. Conde)
European Conferences on Biomedical Optics, Munich, Germany, May 2013. [BibTeX]
@inproceedings{EguizabalGarciaallendeJentoft:2013:Principal-Component-Analysis-to-extract-blood,
abstract = {Endogenous tissue contrast such as decreased hemoglobin saturation aids in cancer localization. Principal component analysis is proposed for blindly oxygenation extraction from total diffuse reflectance spectra obtained by the diffusion approximation.},
address = {Munich, Germany},
author = {Alma Eguizabal and Pilar Garcia-Allende and Karin Jentoft and Panagiotis Symvoulidis and Jose Lopez-Higuera and Vasilis Ntziachristos and Olga M. Conde},
booktitle = {European Conferences on Biomedical Optics},
month = {{M}ay},
title = {Principal component analysis to extract blood oxygenation from theoretical modeling of total diffuse reflectance spectra},
year = {2013},
}
[Abstract]
Endogenous tissue contrast such as decreased hemoglobin saturation aids in cancer localization. Principal component analysis is proposed for blindly oxygenation extraction from total diffuse reflectance spectra obtained by the diffusion approximation.
155
Power-CCA: maximizing the correlation coefficient between the power of projections(
D. Ramírez,
P. J. Schreier,
J. Vía and V. V. Nikulin)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Vancouver, Canada,
May 2013.DOI:10.1109/ICASSP.2013.6638864. [BibTeX]
@inproceedings{RamirezSchreierVia:2013:Power-CCA:-Maximizing-the-Correlation-Coefficient,
abstract = {This work presents a variation of canonical correlation analysis (CCA), where the correlation coefficient between the instantaneous power of the projections is maximized, rather than between the projections themselves. The resulting optimization problem is not convex, and we have to resort to a sub-optimal approach. Concretely, we propose a two-step solution consisting of the singular value decomposition (SVD) of a "coherence" matrix followed by a rank-one matrix approximation. This technique is applied to blindly recovering signals in a model that is motivated by the study of neuronal dynamics in humans using electroencephalography (EEG) and magnetoencephalography (MEG). A distinctive feature of this model is that it allows recovery of amplitude-amplitude coupling between neuronal processes.},
address = {Vancouver, Canada},
author = {D. Ram{\'i}rez and P. J. Schreier and J. V{\'i}a and V. V. Nikulin},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Power-{CCA}: maximizing the correlation coefficient between the power of projections},
year = {2013},
doi = {10.1109/ICASSP.2013.6638864},
}
[Abstract]
This work presents a variation of canonical correlation analysis (CCA), where the correlation coefficient between the instantaneous power of the projections is maximized, rather than between the projections themselves. The resulting optimization problem is not convex, and we have to resort to a sub-optimal approach. Concretely, we propose a two-step solution consisting of the singular value decomposition (SVD) of a "coherence" matrix followed by a rank-one matrix approximation. This technique is applied to blindly recovering signals in a model that is motivated by the study of neuronal dynamics in humans using electroencephalography (EEG) and magnetoencephalography (MEG). A distinctive feature of this model is that it allows recovery of amplitude-amplitude coupling between neuronal processes. 156
Optical coherence tomography assessment of vessel wall degradation in aneurysmatic thoracic aortas
(Eusebio Real, Alma Eguizabal, Alejandro Ponton, J. Fernando Val-Bernal, Marta Mayorga, Jose Revuelta, Jose Lopez-Higuera and Olga Conde)
European Conferences on Biomedical Optics, Munich, Germany, May 2013. [BibTeX]
@inproceedings{RealEguizabalPonton:2013:Optical-Coherence-Tomography-Assesment-of-Vessel,
abstract = {OCT images of human aorta from aneurysms reveals elastin disorder and smooth muscle cell alteration when visualizing the intima and media layers of the aortic wall. Results correlate with pathologist diagnosis in aneurysmatic and control aortas.},
address = {Munich, Germany},
author = {Eusebio Real and Alma Eguizabal and Alejandro Ponton and J. Fernando Val-Bernal and Marta Mayorga and Jose Revuelta and Jose Lopez-Higuera and Olga Conde},
booktitle = {European Conferences on Biomedical Optics},
month = {{M}ay},
title = {Optical coherence tomography assessment of vessel wall degradation in aneurysmatic thoracic aortas},
year = {2013},
}
[Abstract]
OCT images of human aorta from aneurysms reveals elastin disorder and smooth muscle cell alteration when visualizing the intima and media layers of the aortic wall. Results correlate with pathologist diagnosis in aneurysmatic and control aortas.
157
Computing the degrees of freedom for arbitrary MIMO interference channels(
Óscar González,
Christian Lameiro,
Javier Vía,
Carlos Beltrán and Ignacio Santamaría)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Vancouver, Canada,
May 2013.DOI:10.1109/ICASSP.2013.6638491. [BibTeX]
@inproceedings{GonzalezLameiroVia:2013:Computing-the-Degrees-of-Freedom-for-Arbitrary,
abstract = {In this paper we provide an efficient procedure to compute the total number of degrees of freedom (DoF), achievable by linear beamforming, of the $K$-user multiple-input multiple-output (MIMO) interference channel with an arbitrary number of Tx-Rx antennas at each link. Firstly, we derive an analytical outer bound that generalizes the results that exist for the symmetric $K$-user $M\timesN$ interference channel. Secondly, we obtain a tighter bound by solving a convex optimization problem that includes as constraints the DoF characterizations for point-to-point MIMO links and for 2-user interference channels. The solution to this convex problem admits an interesting waterfilling interpretation. Finally, exploiting this outer bound and using a recently proposed feasibility test, we show that it is possible to obtain the DoF for any interference channel in an efficient way. Some simulations results are included to illustrate the tightness of the derived bounds, as well as to study the DoF achievable for the 4-user channel when we distribute the total number of antennas among users and between transmitters and receivers in different ways.},
address = {Vancouver, Canada},
author = {Gonz{\'a}lez, {\'O}scar and Lameiro, Christian and V{\'i}a, Javier and Beltr{\'a}n, Carlos and Santamar{\'i}a, Ignacio},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Computing the degrees of freedom for arbitrary {MIMO} interference channels},
year = {2013},
doi = {10.1109/ICASSP.2013.6638491},
}
[Abstract]
In this paper we provide an efficient procedure to compute the total number of degrees of freedom (DoF), achievable by linear beamforming, of the K-user multiple-input multiple-output (MIMO) interference channel with an arbitrary number of Tx-Rx antennas at each link. Firstly, we derive an analytical outer bound that generalizes the results that exist for the symmetric K-user MtimesN interference channel. Secondly, we obtain a tighter bound by solving a convex optimization problem that includes as constraints the DoF characterizations for point-to-point MIMO links and for 2-user interference channels. The solution to this convex problem admits an interesting waterfilling interpretation. Finally, exploiting this outer bound and using a recently proposed feasibility test, we show that it is possible to obtain the DoF for any interference channel in an efficient way. Some simulations results are included to illustrate the tightness of the derived bounds, as well as to study the DoF achievable for the 4-user channel when we distribute the total number of antennas among users and between transmitters and receivers in different ways. 158
Quantization-loss reduction for signal parameter estimation
(Manuel Stein, Friederike Wendler, Amine Mezghani and Josef A. Nossek)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process., Vancouver, Canada, May 2013. [BibTeX]
@inproceedings{Stein:ICASSP:2013,
address = {Vancouver, Canada},
author = {Stein, Manuel and Wendler, Friederike and Mezghani, Amine and Nossek, Josef A.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Quantization-loss reduction for signal parameter estimation},
year = {2013},
}
[Abstract]
159
Quantization-loss analysis for array signal-source localization
(Manuel Stein, Amine Mezghani and Josef A. Nossek)
Proc. ITG Int. Work. Smart Ant., Stuttgart, Germany, March 2013. [BibTeX]
@inproceedings{Stein:WSA:2013,
address = {Stuttgart, Germany},
author = {Stein, Manuel and Mezghani, Amine and Nossek, Josef A.},
booktitle = {{P}roc.\ {ITG} {I}nt.\ {W}ork.\ Smart Ant.},
month = {{M}arch},
title = {Quantization-loss analysis for array signal-source localization},
year = {2013},
}
[Abstract]
160
Linear classifier and textural analysis of optical scattering images for tumor classification during breast cancer extraction(
Alma Eguizabal,
Ashley M. Laughney,
P. Beatriz Garcia-Allende,
Venkataramanan Krishnaswamy,
Wendy A. Wells,
Keith D. Paulsen,
Brian W. Pogue,
Jose Lopez-Higuera and Olga M. Conde)
SPIE Photonics West BIOS, VIII Biomedical Applications of Light Scattering,
San Francisco, USA,
February 2013. [BibTeX]
@inproceedings{EguizabalLaughneyGarciaallende:2013:Linear-classifier-and-textural-analysis-of-optical-scattering,
abstract = {Texture analysis of light scattering in tissue is proposed to obtain diagnostic information from breast cancer specimens. Light scattering measurements are minimally invasive, and allow the estimation of tissue morphology to guide the surgeon in resection surgeries. The usability of scatter signatures acquired with a micro-sampling reflectance spectral imaging system was improved utilizing an empirical approximation to the Mie theory to estimate the scattering power on a per-pixel basis. Co-occurrence analysis is then applied to the scattering power images to extract the textural features. A statistical analysis of the features demonstrated the suitability of the autocorrelation for the classification of notmalignant (normal epithelia and stroma, benign epithelia and stroma, inflammation), malignant (DCIS, IDC, ILC) and adipose tissue, since it reveals morphological information of tissue. Non-malignant tissue shows higher autocorrelation values while adipose tissue presents a very low autocorrelation on its scatter texture, being malignant the middle ground. Consequently, a fast linear classifier based on the consideration of just one straightforward feature is enough for providing relevant diagnostic information. A leave-one-out validation of the linear classifier on 29 samples with 48 regions of interest showed classification accuracies of 98.74% on adipose tissue, 82.67% on non-malignant tissue and 72.37% on malignant tissue, in comparison with the biopsy H and E gold standard. This demonstrates that autocorrelation analysis of scatter signatures is a very computationally efficient and automated approach to provide pathological information in real-time to guide surgeon during tissue resection.},
address = {San Francisco, USA},
author = {Alma Eguizabal and Ashley M. Laughney and P. Beatriz Garcia-Allende and Venkataramanan Krishnaswamy and Wendy A. Wells and Keith D. Paulsen and Brian W. Pogue and Jose Lopez-Higuera and Olga M. Conde},
booktitle = {SPIE Photonics West BIOS, VIII Biomedical Applications of Light Scattering},
month = {{F}ebruary},
title = {Linear classifier and textural analysis of optical scattering images for tumor classification during breast cancer extraction},
year = {2013},
}
[Abstract]
Texture analysis of light scattering in tissue is proposed to obtain diagnostic information from breast cancer specimens. Light scattering measurements are minimally invasive, and allow the estimation of tissue morphology to guide the surgeon in resection surgeries. The usability of scatter signatures acquired with a micro-sampling reflectance spectral imaging system was improved utilizing an empirical approximation to the Mie theory to estimate the scattering power on a per-pixel basis. Co-occurrence analysis is then applied to the scattering power images to extract the textural features. A statistical analysis of the features demonstrated the suitability of the autocorrelation for the classification of notmalignant (normal epithelia and stroma, benign epithelia and stroma, inflammation), malignant (DCIS, IDC, ILC) and adipose tissue, since it reveals morphological information of tissue. Non-malignant tissue shows higher autocorrelation values while adipose tissue presents a very low autocorrelation on its scatter texture, being malignant the middle ground. Consequently, a fast linear classifier based on the consideration of just one straightforward feature is enough for providing relevant diagnostic information. A leave-one-out validation of the linear classifier on 29 samples with 48 regions of interest showed classification accuracies of 98.74% on adipose tissue, 82.67% on non-malignant tissue and 72.37% on malignant tissue, in comparison with the biopsy H and E gold standard. This demonstrates that autocorrelation analysis of scatter signatures is a very computationally efficient and automated approach to provide pathological information in real-time to guide surgeon during tissue resection. 161
Fractal analysis of scatter imaging signatures to distinguish breast pathologies(
Alma Eguizabal,
Ashley M. Laughney,
Venkataramanan Krishnaswamy,
Wendy A. Wells,
Keith D. Paulsen,
Brian W. Pogue,
Jose Lopez-Higuera and Olga M. Conde)
SPIE Photonics West BIOS, VIII Biomedical Applications of Light Scattering,
San Francisco, USA,
February 2013. [BibTeX]
@inproceedings{EguizabalLaughneyKrishnaswamy:2013:Fractal-analysis-of-scatter-imaging-signatures,
abstract = {Fractal analysis combined with a label-free scattering technique is proposed for describing the pathological architecture of tumors. Clinicians and pathologists are conventionally trained to classify abnormal features such as structural irregularities or high indices of mitosis. The potential of fractal analysis lies in the fact of being a morphometric measure of the irregular structures providing a measure of the object's complexity and self-similarity. As cancer is characterized by disorder and irregularity in tissues, this measure could be related to tumor growth. Fractal analysis has been probed in the understanding of the tumor vasculature network. This work addresses the feasibility of applying fractal analysis to the scattering power map (as a physical modeling) and principal components (as a statistical modeling) provided by a localized reflectance spectroscopic system. Disorder, irregularity and cell size variation in tissue samples is translated into the scattering power and principal components magnitude and its fractal dimension is correlated with the pathologist assessment of the samples. The fractal dimension is computed applying the box-counting technique. Results show that fractal analysis of ex-vivo fresh tissue samples exhibits separated ranges of fractal dimension that could help classifier combining the fractal results with other morphological features. This contrast trend would help in the discrimination of tissues in the intraoperative context and may serve as a useful adjunct to surgeons.},
address = {San Francisco, USA},
author = {Alma Eguizabal and Ashley M. Laughney and Venkataramanan Krishnaswamy and Wendy A. Wells and Keith D. Paulsen and Brian W. Pogue and Jose Lopez-Higuera and Olga M. Conde},
booktitle = {SPIE Photonics West BIOS, VIII Biomedical Applications of Light Scattering},
month = {{F}ebruary},
title = {Fractal analysis of scatter imaging signatures to distinguish breast pathologies},
year = {2013},
}
[Abstract]
Fractal analysis combined with a label-free scattering technique is proposed for describing the pathological architecture of tumors. Clinicians and pathologists are conventionally trained to classify abnormal features such as structural irregularities or high indices of mitosis. The potential of fractal analysis lies in the fact of being a morphometric measure of the irregular structures providing a measure of the object's complexity and self-similarity. As cancer is characterized by disorder and irregularity in tissues, this measure could be related to tumor growth. Fractal analysis has been probed in the understanding of the tumor vasculature network. This work addresses the feasibility of applying fractal analysis to the scattering power map (as a physical modeling) and principal components (as a statistical modeling) provided by a localized reflectance spectroscopic system. Disorder, irregularity and cell size variation in tissue samples is translated into the scattering power and principal components magnitude and its fractal dimension is correlated with the pathologist assessment of the samples. The fractal dimension is computed applying the box-counting technique. Results show that fractal analysis of ex-vivo fresh tissue samples exhibits separated ranges of fractal dimension that could help classifier combining the fractal results with other morphological features. This contrast trend would help in the discrimination of tissues in the intraoperative context and may serve as a useful adjunct to surgeons. 162
Quantization-loss reduction for 1-bit BOC positioning
(Friederike Wendler, Manuel Stein, Amine Mezghani and Josef A. Nossek)
ION Int. Tech. Meet., San Diego, USA, January 2013. [BibTeX]
@inproceedings{Wendler:ITM:2013,
address = {San Diego, USA},
author = {Wendler, Friederike and Stein, Manuel and Mezghani, Amine and Nossek, Josef A.},
booktitle = {{ION} {I}nt.\ {T}ech.\ Meet.},
month = {{J}anuary},
title = {Quantization-loss reduction for 1-bit {BOC} positioning},
year = {2013},
}
[Abstract]
163
Small gain theorems for large scale systems and construction of ISS Lyapunov functions
(Sergey N. Dashkovskiy, Björn S. Rüffer and Fabian R. Wirth)
Proc. 51st IEEE Conf. Decis. Control, pp. 4165–4170, Maui, Hawaii, USA, 2012. [BibTeX]
@inproceedings{dashkovskiyrufferwirth2012-small-gain-theorems-for-large-scale-systems-and-construction-of-iss-lyapunov-functions,
abstract = {This invited paper is a significantly shortened excerpt of the article S. N. DASHKOVSKIY, B. S. R{\"U}FFER, AND F. R. WIRTH, Small gain theorems for large scale systems and construction of ISS Lyapunov functions, SIAM J. Control Optim., 48 (2010), pp. 4089–4118. We consider interconnections of n nonlinear subsystems in the input-to-state stability (ISS) framework. Foreach subsystem an ISS Lyapunov function is given that treats the other subsystems as independent inputs. A gain matrix is used to encode the mutual dependencies of the systems in the network. Under a small gain assumption on the monotone operator induced by the gain matrix, a locally Lipschitz continuous ISS Lyapunov function is obtained constructively for the entire network by appropriately scaling the individualLyapunov functions for the subsystems.},
address = {Maui, Hawaii, USA},
author = {Dashkovskiy, Sergey N. and R{\"u}ffer, Bj{\"o}rn S. and Wirth, Fabian R.},
booktitle = {{P}roc. 51st {IEEE} {C}onf. {D}ecis. {C}ontrol},
title = {Small gain theorems for large scale systems and construction of {ISS} {L}yapunov functions},
year = {2012},
pages = {4165–4170},
}
[Abstract]
This invited paper is a significantly shortened excerpt of the article S. N. DASHKOVSKIY, B. S. R"UFFER, AND F. R. WIRTH, Small gain theorems for large scale systems and construction of ISS Lyapunov functions, SIAM J. Control Optim., 48 (2010), pp. 4089–4118. We consider interconnections of n nonlinear subsystems in the input-to-state stability (ISS) framework. Foreach subsystem an ISS Lyapunov function is given that treats the other subsystems as independent inputs. A gain matrix is used to encode the mutual dependencies of the systems in the network. Under a small gain assumption on the monotone operator induced by the gain matrix, a locally Lipschitz continuous ISS Lyapunov function is obtained constructively for the entire network by appropriately scaling the individualLyapunov functions for the subsystems.
164
A cyclic small-gain condition and an equivalent matrix-like criterion for iISS networks
(Hiroshi Ito, Zhong-Ping Jiang, Sergey N. Dashkovskiy and Björn S. Rüffer)
Proc. 51st IEEE Conf. Decis. Control, pp. 4158–4164, Maui, Hawaii, USA, 2012. [BibTeX]
@inproceedings{itojiangdashkovskiyruffer2012-a-cyclic-small-gain-condition-and-an-equivalent-matrix-like-criterion-for-iiss-networks,
abstract = {This paper considers nonlinear dynamical networks consisting of individually iISS (integral input-to-statestable) subsystems which are not necessarily ISS (input-to-statestable). Stability criteria for internal and external stability of the networks are developed in view of both necessity and sufficiency. For the sufficiency, we show how we can construct a Lyapunov function of the network explicitly under the assumption that a cyclic small-gain condition is satisfied. The cyclic small-gain condition is shown to be equivalent to a matrix-like condition. The two conditions and their equivalence precisely generalize some central ISS results in the literature. Moreover, the necessity of the matrix-like condition is established. The allowable number of non-ISS subsystems for stability of the network is discussed through several necessity conditions.},
address = {Maui, Hawaii, USA},
author = {Ito, Hiroshi and Jiang, Zhong-Ping and Dashkovskiy, Sergey N. and R{\"u}ffer, Bj{\"o}rn S.},
booktitle = {{P}roc. 51st {IEEE} {C}onf. {D}ecis. {C}ontrol},
title = {A cyclic small-gain condition and an equivalent matrix-like criterion for {iISS} networks},
year = {2012},
pages = {4158–4164},
}
[Abstract]
This paper considers nonlinear dynamical networks consisting of individually iISS (integral input-to-statestable) subsystems which are not necessarily ISS (input-to-statestable). Stability criteria for internal and external stability of the networks are developed in view of both necessity and sufficiency. For the sufficiency, we show how we can construct a Lyapunov function of the network explicitly under the assumption that a cyclic small-gain condition is satisfied. The cyclic small-gain condition is shown to be equivalent to a matrix-like condition. The two conditions and their equivalence precisely generalize some central ISS results in the literature. Moreover, the necessity of the matrix-like condition is established. The allowable number of non-ISS subsystems for stability of the network is discussed through several necessity conditions.
165
From convergent dynamics to incremental stability
(Björn S. Rüffer, Nathan van de Wouw and Markus Mueller)
Proc. 51st IEEE Conf. Decis. Control, pp. 2958–2963, Maui, Hawaii, USA, 2012. [BibTeX]
@inproceedings{rufferwouwmueller2012-from-convergent-dynamics-to-incremental-stability,
abstract = {This paper advocates that the convergent systems property and incremental stability are two intimately related though different properties. Sufficient conditions for the convergent systems property usually rely upon first showing that a system is incrementally stable, as e.g. in the celebrated Demidovich condition. However, in the current paper it is shown that incremental stability itself does not imply the convergence property, or vice versa. Moreover, characterizations of both properties in terms of Lyapunov functions are given. Based on these characterizations, it is established that the convergence property implies incremental stability for systems evolving oncompact sets, and also when a suitable uniformity condition is satisfied.},
address = {Maui, Hawaii, USA},
author = {R{\"u}ffer, Bj{\"o}rn S. and van de Wouw, Nathan and Mueller, Markus},
booktitle = {{P}roc. 51st {IEEE} {C}onf. {D}ecis. {C}ontrol},
title = {From convergent dynamics to incremental stability},
year = {2012},
pages = {2958–2963},
}
[Abstract]
This paper advocates that the convergent systems property and incremental stability are two intimately related though different properties. Sufficient conditions for the convergent systems property usually rely upon first showing that a system is incrementally stable, as e.g. in the celebrated Demidovich condition. However, in the current paper it is shown that incremental stability itself does not imply the convergence property, or vice versa. Moreover, characterizations of both properties in terms of Lyapunov functions are given. Based on these characterizations, it is established that the convergence property implies incremental stability for systems evolving oncompact sets, and also when a suitable uniformity condition is satisfied.
166
GLRT for testing separability of a complex-valued mixture based on the strong uncorrelating transform(
D. Ramírez,
P. J. Schreier,
J. Vía and I. Santamaría)
Proc. IEEE Int. Work. Machine Learning for Signal Process.,
Santander, Spain,
September 2012.DOI:10.1109/MLSP.2012.6349785. [BibTeX]
@inproceedings{RamirezSchreierVia:2012:GLRT-For-Testing-Separability-Of-A-Complex-Valued,
abstract = {The Strong Uncorrelating Transform (SUT) allows blind separation of a mixture of complex independent sources if and only if all sources have distinct circularity coefficients. In practice, the circularity coefficients need to be estimated from observed data. We propose a generalized likelihood ratio test (GLRT) for separability of a complex mixture using the SUT, based on estimated circularity coefficients. For distinct circularity coefficients (separable case), the maximum likelihood (ML) estimates, required for the GLRT, are straightforward. However, for circularity coefficients with multiplicity larger than one (non-separable case), the ML estimates are much more difficult to find. Numerical simulations show the good performance of the proposed detector.},
address = {Santander, Spain},
author = {D. Ram{\'i}rez and P. J. Schreier and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {W}ork.\ Machine Learning for Signal Process.},
month = {{S}eptember},
title = {{GLRT} for testing separability of a complex-valued mixture based on the strong uncorrelating transform},
year = {2012},
doi = {10.1109/MLSP.2012.6349785},
}
[Abstract]
The Strong Uncorrelating Transform (SUT) allows blind separation of a mixture of complex independent sources if and only if all sources have distinct circularity coefficients. In practice, the circularity coefficients need to be estimated from observed data. We propose a generalized likelihood ratio test (GLRT) for separability of a complex mixture using the SUT, based on estimated circularity coefficients. For distinct circularity coefficients (separable case), the maximum likelihood (ML) estimates, required for the GLRT, are straightforward. However, for circularity coefficients with multiplicity larger than one (non-separable case), the ML estimates are much more difficult to find. Numerical simulations show the good performance of the proposed detector. 167
The random monogenic signal(
S. C. Olhede,
D. Ramírez and P. J. Schreier)
Proc. IEEE Int. Conf. Image Process.,
Orlando, Florida, USA,
September 2012.DOI:10.1109/ICIP.2012.6467404. [BibTeX]
@inproceedings{OlhedeRamirezSchreier:2012:The-Random-Monogenic-Signal,
abstract = {The monogenic signal allows us to decompose a two-dimensional real signal into a local amplitude, a local orientation, and a local phase. In this paper, we introduce the random monogenic signal and study its second-order statistical properties. The monogenic signal may be represented as a quaternion-valued signal. We show that for homogeneous random fields, we need exactly two quaternion-valued covariance functions for a complete second-order description. We also introduce a stochastic model for unidirectional signals and a measure of unidirectionality.},
address = {Orlando, Florida, USA},
author = {S. C. Olhede and D. Ram{\'i}rez and P. J. Schreier},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {I}mage {P}rocess.},
month = {{S}eptember},
title = {The random monogenic signal},
year = {2012},
doi = {10.1109/ICIP.2012.6467404},
}
[Abstract]
The monogenic signal allows us to decompose a two-dimensional real signal into a local amplitude, a local orientation, and a local phase. In this paper, we introduce the random monogenic signal and study its second-order statistical properties. The monogenic signal may be represented as a quaternion-valued signal. We show that for homogeneous random fields, we need exactly two quaternion-valued covariance functions for a complete second-order description. We also introduce a stochastic model for unidirectional signals and a measure of unidirectionality. 168
Pre- and post-FFT Interference Leakage Minimization for MIMO OFDM networks(
Christian Lameiro,
Óscar González,
Javier Vía,
Ignacio Santamaría and Robert W. Heath Jr.)
Proc. Int. Symp. Wireless Comm. Syst.,
Paris, France,
August 2012.DOI:10.1109/ISWCS.2012.6328429. [BibTeX]
@inproceedings{LameiroGonzalezVia:2012:Pre–and-Post-FFT-Interference-Leakage,
abstract = {Interference alignment (IA) has been shown to achieve the maximum degrees of freedom in the multiple-input multiple-output (MIMO) K-user interference channel (IFC). In the presence of frequency-selective channels, orthogonal frequency-division multiplexing (OFDM) is typically used to deal with the multipath nature of the channel. While IA techniques can be applied in a per-subcarrier basis (post-FFT), the existence of symbol timing offsets (STOs) between the desired and the interfering OFDM symbols decreases the system performance dramatically. To solve this problem, we design pre-FFT precoders and decoders for single-beam MIMO IFCs for OFDM transmissions. Since the IA decoders operate before the FFT, they mitigate the interference before synchronization takes place. We show that our proposed scheme improves the system performance when STOs occur, in comparison with traditional post-FFT IA techniques. We provide simulation results to compare post- and pre-FFT beamforming techniques and to illustrate the performance of the proposed method.},
address = {Paris, France},
author = {Lameiro, Christian and Gonz{\'a}lez, {\'O}scar and V{\'i}a, Javier and Santamar{\'i}a, Ignacio and Heath Jr., Robert W.},
booktitle = {Proc. Int. Symp. Wireless Comm. Syst.},
month = {{A}ugust},
title = {Pre- and post-{FFT} Interference Leakage Minimization for {MIMO OFDM} networks},
year = {2012},
doi = {10.1109/ISWCS.2012.6328429},
}
[Abstract]
Interference alignment (IA) has been shown to achieve the maximum degrees of freedom in the multiple-input multiple-output (MIMO) K-user interference channel (IFC). In the presence of frequency-selective channels, orthogonal frequency-division multiplexing (OFDM) is typically used to deal with the multipath nature of the channel. While IA techniques can be applied in a per-subcarrier basis (post-FFT), the existence of symbol timing offsets (STOs) between the desired and the interfering OFDM symbols decreases the system performance dramatically. To solve this problem, we design pre-FFT precoders and decoders for single-beam MIMO IFCs for OFDM transmissions. Since the IA decoders operate before the FFT, they mitigate the interference before synchronization takes place. We show that our proposed scheme improves the system performance when STOs occur, in comparison with traditional post-FFT IA techniques. We provide simulation results to compare post- and pre-FFT beamforming techniques and to illustrate the performance of the proposed method. 169
The locally most powerful invariant test for detecting a rank-P Gaussian signal in white noise(
D. Ramírez,
J. Iscar,
J. Vía,
I. Santamaría and L. L. Scharf)
Proc. IEEE Sensor Array and Multichannel Signal Process. Work.,
Hoboken, NJ, USA,
June 2012.DOI:10.1109/SAM.2012.6250547. [BibTeX]
@inproceedings{RamirezIscarVia:2012:The-Locally-Most-Powerful-Invariant,
abstract = {Spectrum sensing has become one of the main components of a cognitive transmitter. Conventional detectors suffer from noise power uncertainties and multiantenna detectors have been proposed to overcome this difficulty, and to improve the detection performance. However, most of the proposed multiantenna detectors are based on non-optimal techniques, such as the generalized likelihood ratio test (GLRT), or even heuristic approaches that are not based on first principles. In this work, we derive the locally most powerful invariant test (LMPIT), that is, the optimal invariant detector for close hypotheses, or equivalently, for a low signal-to-noise ratio (SNR). The traditional approach, based on the distributions of the maximal invariant statistic, is avoided thanks to Wijsman's theorem, which does not need these distributions. Our findings show that, in the low SNR regime, and in contrast to the GLRT, the additional spatial structure imposed by the signal model is irrelevant for optimal detection. Finally, we use Monte Carlo simulations to illustrate the good performance of the LMPIT.},
address = {Hoboken, NJ, USA},
author = {D. Ram{\'i}rez and J. Iscar and J. V{\'i}a and I. Santamar{\'i}a and L. L. Scharf},
booktitle = {{P}roc.\ {IEEE} {S}ensor {A}rray and {M}ultichannel {S}ignal {P}rocess. {W}ork.},
month = {{J}une},
title = {The locally most powerful invariant test for detecting a {rank-$P$} {G}aussian signal in white noise},
year = {2012},
doi = {10.1109/SAM.2012.6250547},
}
[Abstract]
Spectrum sensing has become one of the main components of a cognitive transmitter. Conventional detectors suffer from noise power uncertainties and multiantenna detectors have been proposed to overcome this difficulty, and to improve the detection performance. However, most of the proposed multiantenna detectors are based on non-optimal techniques, such as the generalized likelihood ratio test (GLRT), or even heuristic approaches that are not based on first principles. In this work, we derive the locally most powerful invariant test (LMPIT), that is, the optimal invariant detector for close hypotheses, or equivalently, for a low signal-to-noise ratio (SNR). The traditional approach, based on the distributions of the maximal invariant statistic, is avoided thanks to Wijsman's theorem, which does not need these distributions. Our findings show that, in the low SNR regime, and in contrast to the GLRT, the additional spatial structure imposed by the signal model is irrelevant for optimal detection. Finally, we use Monte Carlo simulations to illustrate the good performance of the LMPIT. 170
Bayesian multiantenna sensing for cognitive radio(
J. Manco-Vásquez,
M. Lazaro-Gredilla,
D. Ramírez,
J. Vía and I. Santamaría)
Proc. IEEE Sensor Array and Multichannel Signal Process. Work.,
Hoboken, NJ, USA,
June 2012.DOI:10.1109/SAM.2012.6250566. [BibTeX]
@inproceedings{Manco-VasquezLazaro-GredillaRamirez:2012:Bayesian-Multiantenna-Sensing-for-Cognitive,
abstract = {In this paper, the problem of multiantenna spectrum sensing in cognitive radio (CR) is addressed within a Bayesian framework. Unlike previous works, our Bayesian model places priors directly on the spatial covariance matrices under both hypotheses, as well as on the probability of channel occupancy. Specifically, we use inverse-gamma and complex inverse-Wishart distributions as conjugate priors for the null and alternative hypotheses, respectively; and a Bernoulli distribution as the prior for channel occupancy. At each sensing period, Bayesian inference is applied and the posterior of channel occupancy is thresholded for detection. After a suitable approximation, the posteriors are employed as priors for the next sensing frame, which can be beneficial in slowly time-varying environments. By means of simulations, the proposed detector is shown to outperform the Generalized Likelihood Ratio Test (GLRT) detector.},
address = {Hoboken, NJ, USA},
author = {J. Manco-V{\'a}squez and M. Lazaro-Gredilla and D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {S}ensor {A}rray and {M}ultichannel {S}ignal {P}rocess. {W}ork.},
month = {{J}une},
title = {Bayesian multiantenna sensing for cognitive radio},
year = {2012},
doi = {10.1109/SAM.2012.6250566},
}
[Abstract]
In this paper, the problem of multiantenna spectrum sensing in cognitive radio (CR) is addressed within a Bayesian framework. Unlike previous works, our Bayesian model places priors directly on the spatial covariance matrices under both hypotheses, as well as on the probability of channel occupancy. Specifically, we use inverse-gamma and complex inverse-Wishart distributions as conjugate priors for the null and alternative hypotheses, respectively; and a Bernoulli distribution as the prior for channel occupancy. At each sensing period, Bayesian inference is applied and the posterior of channel occupancy is thresholded for detection. After a suitable approximation, the posteriors are employed as priors for the next sensing frame, which can be beneficial in slowly time-varying environments. By means of simulations, the proposed detector is shown to outperform the Generalized Likelihood Ratio Test (GLRT) detector. 171
A distributed algorithm for two-way multiple-relay networks(
Christian Lameiro,
Javier Vía and Ignacio Santamaría)
Proc. IEEE Sensor Array and Multichannel Signal Process. Work.,
Hoboken, NJ, USA,
June 2012.DOI:10.1109/SAM.2012.6250440. [BibTeX]
@inproceedings{LameiroViaSantamaria:2012:A-Distributed-Algorithm-for-Two-Way-Multiple-Relay,
abstract = {In this paper we propose an efficient transmission strategy for the two-way relay channel (TWRC) with multiple relays, when these are multiple-input multiple-output (MIMO) transceivers that apply the amplify-and-forward (AF) protocol. Although the optimal beamforming strategy is known, it requires a central node, with channel state information (CSI) of the entire network, to compute all the beamforming matrices, which is impractical. To reduce the overhead, in this paper we present a distributed algorithm for the computation of the relay beamforming matrices. The proposed algorithm divides the problem in two stages. First, each relay computes its own beamforming matrix in parallel using only local CSI. Next, a distributed beamforming is applied to make the signals add up coherently at the nodes. Although the proposed algorithm is suboptimal, we show through simulations that it performs very close to the optimal achievable rate region.},
address = {Hoboken, NJ, USA},
author = {Lameiro, Christian and V{\'i}a, Javier and Santamar{\'i}a, Ignacio},
booktitle = {{P}roc.\ {IEEE} {S}ensor {A}rray and {M}ultichannel {S}ignal {P}rocess. {W}ork.},
month = {{J}une},
title = {A distributed algorithm for two-way multiple-relay networks},
year = {2012},
doi = {10.1109/SAM.2012.6250440},
}
[Abstract]
In this paper we propose an efficient transmission strategy for the two-way relay channel (TWRC) with multiple relays, when these are multiple-input multiple-output (MIMO) transceivers that apply the amplify-and-forward (AF) protocol. Although the optimal beamforming strategy is known, it requires a central node, with channel state information (CSI) of the entire network, to compute all the beamforming matrices, which is impractical. To reduce the overhead, in this paper we present a distributed algorithm for the computation of the relay beamforming matrices. The proposed algorithm divides the problem in two stages. First, each relay computes its own beamforming matrix in parallel using only local CSI. Next, a distributed beamforming is applied to make the signals add up coherently at the nodes. Although the proposed algorithm is suboptimal, we show through simulations that it performs very close to the optimal achievable rate region. 172
ICA-guided delineation of breast cancer pathology(
Alma Eguizabal,
Ashley M. Laughney,
P. Beatriz Garcia-Allende,
Venkataramanan Krishnaswamy,
Wendy A. Wells,
Keith D. Paulsen,
Brian W. Pogue,
Jose M. Lopez-Higuera and Olga M. Conde)
IEEE 9th International Symposium on Biomedical Imaging,
Barcelona, Spain,
May 2012. [BibTeX]
@inproceedings{EguizabalLaughneyGarciaallende:2012:ICA-guided-delineation-of-breast-cancer,
abstract = {A surgeon-guided independent component analysis from optical reflectance measurements is proposed for breast tumor delineation. Independent Component Analysis is first applied to extract the most relevant features from local measures of broadband reflectance and then a tumor probability indicator is obtained and provided utilizing surgeon assistance to resolve the inherent ambiguities in the independent component calculation. A set of 29 breast tissue samples have been diagnosed achieving a sensitivity of 90.57%, and specificity of 93.98%.},
address = {Barcelona, Spain},
author = {Alma Eguizabal and Ashley M. Laughney and P. Beatriz Garcia-Allende and Venkataramanan Krishnaswamy and Wendy A. Wells and Keith D. Paulsen and Brian W. Pogue and Jose M. Lopez-Higuera and Olga M. Conde},
booktitle = {IEEE 9th International Symposium on Biomedical Imaging},
month = {{M}ay},
title = {{ICA}-guided delineation of breast cancer pathology},
year = {2012},
}
[Abstract]
A surgeon-guided independent component analysis from optical reflectance measurements is proposed for breast tumor delineation. Independent Component Analysis is first applied to extract the most relevant features from local measures of broadband reflectance and then a tumor probability indicator is obtained and provided utilizing surgeon assistance to resolve the inherent ambiguities in the independent component calculation. A set of 29 breast tissue samples have been diagnosed achieving a sensitivity of 90.57%, and specificity of 93.98%. 173
Textural analysis of optical scattering for identification of cancer in breast surgical specimens(
Alma Eguizabal,
Ashley M. Laughney,
P. Beatriz Garcia-Allende,
Venkataramanan Krishnaswamy,
Wendy A. Wells,
Keith D. Paulsen,
Brian W. Pogue,
Jose M. Lopez-Higuera and Olga M. Conde)
IEEE 9th International Symposium on Biomedical Imaging,
Barcelona, Spain,
May 2012. [BibTeX]
@inproceedings{EguizabalLaughneyGarciaallende:2012:Textural-analysis-of-optical-scattering,
abstract = {Textural analysis of tissue scattering images is proposed for healthy versus tumor discrimination. Scattering center density varies from normal to tumor tissues and this variation is translated into different textures in the scattering power map. Adipose tissue shows low autocorrelation values while tumor tissues present higher entropies than normal tissue. Consequently, a combination of autocorrelation and entropy values allows ready tissue discrimination by a supervised linear classifier. The proposed approach has been validated over a set of 29 breast tissue samples achieving a sensitivity of 73.59% and specificity of 82.40%.},
address = {Barcelona, Spain},
author = {Alma Eguizabal and Ashley M. Laughney and P. Beatriz Garcia-Allende and Venkataramanan Krishnaswamy and Wendy A. Wells and Keith D. Paulsen and Brian W. Pogue and Jose M. Lopez-Higuera and Olga M. Conde},
booktitle = {IEEE 9th International Symposium on Biomedical Imaging},
month = {{M}ay},
title = {Textural analysis of optical scattering for identification of cancer in breast surgical specimens},
year = {2012},
}
[Abstract]
Textural analysis of tissue scattering images is proposed for healthy versus tumor discrimination. Scattering center density varies from normal to tumor tissues and this variation is translated into different textures in the scattering power map. Adipose tissue shows low autocorrelation values while tumor tissues present higher entropies than normal tissue. Consequently, a combination of autocorrelation and entropy values allows ready tissue discrimination by a supervised linear classifier. The proposed approach has been validated over a set of 29 breast tissue samples achieving a sensitivity of 73.59% and specificity of 82.40%. 174
Multi-satellite time-delay estimation for reliable high-resolution GNSS receivers
(Christoph Enneking, Manuel Stein, Mario Castañeda, Felix Antreich and Josef A. Nossek)
Proc. IEEE/ION Pos. Nav. Symp., Myrtle Beach, USA, April 2012. [BibTeX]
@inproceedings{Enneking:PLANS:2012,
address = {Myrtle Beach, USA},
author = {Enneking, Christoph and Stein, Manuel and Casta{\~n}eda, Mario and Antreich, Felix and Nossek, Josef A.},
booktitle = {{P}roc.\ {IEEE}{\/}{ION} {P}os. {N}av.\ Symp.},
month = {{A}pril},
title = {Multi-satellite time-delay estimation for reliable high-resolution {GNSS} receivers},
year = {2012},
}
[Abstract]
175
The locally most powerful test for multiantenna spectrum sensing with uncalibrated receivers(
D. Ramírez,
J. Vía and I. Santamaría)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Kyoto, Japan,
March 2012.DOI:10.1109/ICASSP.2012.6288655. [BibTeX]
@inproceedings{RamirezViaSantamaria:2012:The-Locally-Most-Powerful-Test,
abstract = {Spectrum sensing is a key component of the cognitive radio (CR) paradigm. Among CR detectors, multiantenna detectors are gaining popularity since they improve the detection performance and are robust to noise uncertainties. Traditional approaches to multiantenna spectrum sensing are based on the generalized likelihood ratio test (GLRT) or other heuristic detectors, which are not optimal in the Neyman-Pearson sense. In this work, we derive the locally most powerful invariant test (LMPIT), which is the optimal detector, among those preserving the problem invariances, in the low SNR regime. In particular, we apply Wijsman's theorem, which provides us an alternative way to derive the ratio of the distributions of the maximal invariant statistic. Finally, numerical simulations illustrate the performance of the proposed detector.},
address = {Kyoto, Japan},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {The locally most powerful test for multiantenna spectrum sensing with uncalibrated receivers},
year = {2012},
doi = {10.1109/ICASSP.2012.6288655},
}
[Abstract]
Spectrum sensing is a key component of the cognitive radio (CR) paradigm. Among CR detectors, multiantenna detectors are gaining popularity since they improve the detection performance and are robust to noise uncertainties. Traditional approaches to multiantenna spectrum sensing are based on the generalized likelihood ratio test (GLRT) or other heuristic detectors, which are not optimal in the Neyman-Pearson sense. In this work, we derive the locally most powerful invariant test (LMPIT), which is the optimal detector, among those preserving the problem invariances, in the low SNR regime. In particular, we apply Wijsman's theorem, which provides us an alternative way to derive the ratio of the distributions of the maximal invariant statistic. Finally, numerical simulations illustrate the performance of the proposed detector. 176
Interference leakage minimization for convolutive MIMO interference channels(
Óscar González,
Christian Lameiro,
Javier Vía,
Ignacio Santamaría and Robert W. Heath Jr.)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Kyoto, Japan,
March 2012.DOI:10.1109/ICASSP.2012.6288506. [BibTeX]
@inproceedings{GonzalezLameiroVia:2012:Interference-Leakage-Minimization-for-Convolutive,
abstract = {An alternating optimization algorithm was recently proposed for the K-user multiple-input multiple-output (MIMO) interference channel. For flat-fading channels and feasible problems, this algorithm successfully aligns the interfering signals exploiting the spatial dimensions. In this paper, we consider the case in which all pairwise MIMO channels are frequency-selective (convolutive), and the users transmit broadband signals using a single-carrier scheme. Unlike the flat-fading case, for frequency-selective channels it is necessary to add a spectral mask in the frequency response of the precoders and decoders to avoid trivial solutions. We show in the paper that each step of the alternating minimization algorithm can be reformulated as a convex optimization problem in which the autocorrelation function of the precoders or decoders is obtained. Upon convergence, a final spectral factorization stage must be applied to obtain the precoders and decoders from their autocorrelation functions. Simulation results are provided to illustrate the performance of the proposed algorithm.},
address = {Kyoto, Japan},
author = {Gonz{\'a}lez, {\'O}scar and Lameiro, Christian and V{\'i}a, Javier and Santamar{\'i}a, Ignacio and Heath Jr., Robert W.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Interference leakage minimization for convolutive {MIMO} interference channels},
year = {2012},
doi = {10.1109/ICASSP.2012.6288506},
}
[Abstract]
An alternating optimization algorithm was recently proposed for the K-user multiple-input multiple-output (MIMO) interference channel. For flat-fading channels and feasible problems, this algorithm successfully aligns the interfering signals exploiting the spatial dimensions. In this paper, we consider the case in which all pairwise MIMO channels are frequency-selective (convolutive), and the users transmit broadband signals using a single-carrier scheme. Unlike the flat-fading case, for frequency-selective channels it is necessary to add a spectral mask in the frequency response of the precoders and decoders to avoid trivial solutions. We show in the paper that each step of the alternating minimization algorithm can be reformulated as a convex optimization problem in which the autocorrelation function of the precoders or decoders is obtained. Upon convergence, a final spectral factorization stage must be applied to obtain the precoders and decoders from their autocorrelation functions. Simulation results are provided to illustrate the performance of the proposed algorithm. 177
Regularized linear equalization for multipath channels with imperfect channel estimation(
Jun Tong and Peter J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 3009–3012,
March 2012.DOI:10.1109/ICASSP.2012.6288548. [BibTeX]
@inproceedings{TongSchreier:2012:Regularized-linear-equalization-for-mult,
abstract = {This paper deals with different techniques for linear equalization (LE) of multipath channels with imperfect channel estimation (CE). We develop a unified framework based on Krylov subspace expansion, which allows us to compare the performance of the conjugate gradient (CG) method, diagonal loading (DL), and a hybrid scheme. Our analysis shows that the DL method generally outperforms its alternatives, but at the cost of higher complexity. However, we also demonstrate that a proper implementation of the low-complexity CG method can also approach the performance of DL. Finally, we show that preconditioning degrades performance when the CE is poor.},
author = {Tong, Jun and Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Regularized linear equalization for multipath channels with imperfect channel estimation},
year = {2012},
pages = {3009–3012},
doi = {10.1109/ICASSP.2012.6288548},
}
[Abstract]
This paper deals with different techniques for linear equalization (LE) of multipath channels with imperfect channel estimation (CE). We develop a unified framework based on Krylov subspace expansion, which allows us to compare the performance of the conjugate gradient (CG) method, diagonal loading (DL), and a hybrid scheme. Our analysis shows that the DL method generally outperforms its alternatives, but at the cost of higher complexity. However, we also demonstrate that a proper implementation of the low-complexity CG method can also approach the performance of DL. Finally, we show that preconditioning degrades performance when the CE is poor. 178
Blind breast tissue diagnosis using independent component analysis of localized backscattering response(
Alma Eguizabal,
Ashley M. Laughney,
P. Beatriz Garcia-Allende,
Venkataramanan Krishnaswamy,
Wendy A. Wells,
Keith D. Paulsen,
Brian W. Pogue,
Jose Lopez-Higuera and Olga M. Conde)
SPIE Photonics West BIOS, VI Biomedical Applications of Light Scattering,
San Francisco, USA,
January 2012. [BibTeX]
@inproceedings{EguizabalLaughneyGarciaallende:2012:Blind-breast-tissue-diagnosis,
abstract = {A blind separation technique based on Independent Component Analysis (ICA) is proposed for breast tumor delineation and pathologic diagnosis. Tissue morphology is determined by fitting local measures of tissue reflectance to a Mie theory approximation, parameterizing the scattering power, scattering amplitude and average scattering irradiance. ICA is applied on the scattering parameters by spatial analysis using the Fast ICA method to extract more determinant features for an accurate diagnostic. Neither training, nor comparisons with reference parameters are required. Tissue diagnosis is provided directly following ICA application to the scattering parameter images. Surgically resected breast tissues were imaged and identified by a pathologist. Three different tissue pathologies were identified in 29 samples and classified as not-malignant, malignant and adipose. Scatter plot analysis of both ICA results and optical parameters where obtained. ICA subtle ameliorates those cases where optical parameter's scatter plots were not linearly separable. Furthermore, observing the mixing matrix of the ICA, it can be decided when the optical parameters themselves are diagnostically powerful. Moreover, contrast maps provided by ICA correlate with the pathologic diagnosis. The time response of the diagnostic strategy is therefore enhanced comparing with complex classifiers, enabling near real-time assessment of pathology during breast-conserving surgery.},
address = {San Francisco, USA},
author = {Alma Eguizabal and Ashley M. Laughney and P. Beatriz Garcia-Allende and Venkataramanan Krishnaswamy and Wendy A. Wells and Keith D. Paulsen and Brian W. Pogue and Jose Lopez-Higuera and Olga M. Conde},
booktitle = {SPIE Photonics West BIOS, VI Biomedical Applications of Light Scattering},
month = {{J}anuary},
title = {Blind breast tissue diagnosis using independent component analysis of localized backscattering response},
year = {2012},
}
[Abstract]
A blind separation technique based on Independent Component Analysis (ICA) is proposed for breast tumor delineation and pathologic diagnosis. Tissue morphology is determined by fitting local measures of tissue reflectance to a Mie theory approximation, parameterizing the scattering power, scattering amplitude and average scattering irradiance. ICA is applied on the scattering parameters by spatial analysis using the Fast ICA method to extract more determinant features for an accurate diagnostic. Neither training, nor comparisons with reference parameters are required. Tissue diagnosis is provided directly following ICA application to the scattering parameter images. Surgically resected breast tissues were imaged and identified by a pathologist. Three different tissue pathologies were identified in 29 samples and classified as not-malignant, malignant and adipose. Scatter plot analysis of both ICA results and optical parameters where obtained. ICA subtle ameliorates those cases where optical parameter's scatter plots were not linearly separable. Furthermore, observing the mixing matrix of the ICA, it can be decided when the optical parameters themselves are diagnostically powerful. Moreover, contrast maps provided by ICA correlate with the pathologic diagnosis. The time response of the diagnostic strategy is therefore enhanced comparing with complex classifiers, enabling near real-time assessment of pathology during breast-conserving surgery. 179
Enhanced tumor contrast during breast lumpectomy provided by independent component analysis of localized reflectance measures(
Alma Eguizabal,
Ashley M. Laughney,
P. Beatriz Garcia-Allende,
Venkataramanan Krishnaswamy,
Wendy A. Wells,
Keith D. Paulsen,
Brian W. Pogue,
Jose Lopez-Higuera and Olga M. Conde)
SPIE Photonics West 2012-BIOS, VI Biomedical Applications of Light Scattering,
San Francisco, USA,
January 2012. [BibTeX]
@inproceedings{EguizabalLaughneyGarciaallende:2012:Enhanced-tumor-contrast-during-breast-lumpectomy,
abstract = {A spectral analysis technique to enhance tumor contrast during breast conserving surgery is proposed. A set of 29 surgically-excised breast tissues have been imaged in local reflectance geometry. Measures of broadband reflectance are directly analyzed using Principle Component Analysis (PCA), on a per sample basis, to extract areas of maximal spectral variation. A dynamic selection threshold has been applied to obtain the final number of principal components, accounting for inter-patient variability. A blind separation technique based on Independent Component Analysis (ICA) is then applied to extract diagnostically powerful results. ICA application reveals that the behavior of one independent component highly correlates with the pathologic diagnosis and it surpasses the contrast obtained using empirical models. Moreover, blind detection characteristics (no training, no comparisons with training reference data) and no need for parameterization makes the automated diagnosis simple and time efficient, favoring its translation to the clinical practice. Correlation coefficient with model-based results up to 0.91 has been achieved.},
address = {San Francisco, USA},
author = {Alma Eguizabal and Ashley M. Laughney and P. Beatriz Garcia-Allende and Venkataramanan Krishnaswamy and Wendy A. Wells and Keith D. Paulsen and Brian W. Pogue and Jose Lopez-Higuera and Olga M. Conde},
booktitle = {SPIE Photonics West 2012-BIOS, VI Biomedical Applications of Light Scattering},
month = {{J}anuary},
title = {Enhanced tumor contrast during breast lumpectomy provided by independent component analysis of localized reflectance measures},
year = {2012},
}
[Abstract]
A spectral analysis technique to enhance tumor contrast during breast conserving surgery is proposed. A set of 29 surgically-excised breast tissues have been imaged in local reflectance geometry. Measures of broadband reflectance are directly analyzed using Principle Component Analysis (PCA), on a per sample basis, to extract areas of maximal spectral variation. A dynamic selection threshold has been applied to obtain the final number of principal components, accounting for inter-patient variability. A blind separation technique based on Independent Component Analysis (ICA) is then applied to extract diagnostically powerful results. ICA application reveals that the behavior of one independent component highly correlates with the pathologic diagnosis and it surpasses the contrast obtained using empirical models. Moreover, blind detection characteristics (no training, no comparisons with training reference data) and no need for parameterization makes the automated diagnosis simple and time efficient, favoring its translation to the clinical practice. Correlation coefficient with model-based results up to 0.91 has been achieved. 180
A small-gain theorem and construction of sum-type Lyapunov Functions for Networks of iISS systems
(Hiroshi Ito, Zhong-Ping Jiang, Sergey N. Dashkovskiy and Björn S. Rüffer)
Proc. IEEE American Contr. Conf., pp. 1971–1977, 2011. [BibTeX]
@inproceedings{itojiangdashkovskiyruffer2011-a-small-gain-theorem-and-construction-of-sum-type-lyapunov-functions-for-networks-of-iiss-systems,
abstract = {This paper gives a solution to the problem of verifying stability of networks consisting of integral input-to-state stable (iISS) subsystems. The iISS small-gain theorem developed recently has been restricted to interconnection of two subsystems. For large-scale systems, stability criteria relying only on gain-type information have been successful only in dealing with input-to-state stable stable (ISS) subsystems. To address the stability problem involving iISS subsystems interconnected in general structure, this paper shows how to construct Lyapunov functions of the network by means of nonlinear sum of individual Lyapunov functions of subsystems given in a dissipation formulation under an appropriate small-gain condition.},
author = {Ito, Hiroshi and Jiang, Zhong-Ping and Dashkovskiy, Sergey N. and R{\"u}ffer, Bj{\"o}rn S.},
booktitle = {{P}roc. {IEEE} {A}merican {C}ontr. {C}onf.},
title = {A small-gain theorem and construction of sum-type {L}yapunov Functions for Networks of {iISS} systems},
year = {2011},
pages = {1971–1977},
}
[Abstract]
This paper gives a solution to the problem of verifying stability of networks consisting of integral input-to-state stable (iISS) subsystems. The iISS small-gain theorem developed recently has been restricted to interconnection of two subsystems. For large-scale systems, stability criteria relying only on gain-type information have been successful only in dealing with input-to-state stable stable (ISS) subsystems. To address the stability problem involving iISS subsystems interconnected in general structure, this paper shows how to construct Lyapunov functions of the network by means of nonlinear sum of individual Lyapunov functions of subsystems given in a dissipation formulation under an appropriate small-gain condition.
181
Spatial rank estimation in cognitive radio networks with uncalibrated multiple antennas (invited paper)(
G. Vazquez-Vilar,
D. Ramírez,
R. López-Valcarce,
J. Vía and I. Santamaría)
Proc. Int. Conf. on Cognitive Radio and Advanced Spectrum Management,
Barcelona, Spain,
October 2011.DOI:10.1145/2093256.2093291. [BibTeX]
@inproceedings{Vazquez-VilarRamirezLopez-Valcarce:2011:Spatial-rank-estimation-in-Cognitive,
abstract = {Spectrum sensing is a key component of the Cognitive Radio paradigm. Multiantenna detectors can exploit different spatial features of primary signals in order to boost detection performance and robustness in very low signal-to-noise ratios. However, in several cases these detectors require additional information, such as the rank of the spatial covariance matrix of the received signal. In this work we study the problem of estimating this rank under Gaussianity assumption using an uncalibrated receiver, i.e. with different (unknown) noise levels at each of the antennas.},
address = {Barcelona, Spain},
author = {G. Vazquez-Vilar and D. Ram{\'i}rez and R. L{\'o}pez-Valcarce and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {Proc.\ Int. Conf. on Cognitive Radio and Advanced Spectrum Management},
month = {{O}ctober},
title = {Spatial rank estimation in cognitive radio networks with uncalibrated multiple antennas (invited paper)},
year = {2011},
doi = {10.1145/2093256.2093291},
}
[Abstract]
Spectrum sensing is a key component of the Cognitive Radio paradigm. Multiantenna detectors can exploit different spatial features of primary signals in order to boost detection performance and robustness in very low signal-to-noise ratios. However, in several cases these detectors require additional information, such as the rank of the spatial covariance matrix of the received signal. In this work we study the problem of estimating this rank under Gaussianity assumption using an uncalibrated receiver, i.e. with different (unknown) noise levels at each of the antennas. 182
Recent advances in multiantenna spectrum sensing: complexity, noise uncertainty, and signal rank issues(
G. Vazquez-Vilar,
D. Romero,
R. López-Valcarce,
D. Ramírez,
J. Vía,
I. Santamaría and J. Sala)
Int. Work. COST Action IC0902,
Barcelona, Spain,
October 2011.Extended abstract [BibTeX]
@inproceedings{Vazquez-VilarRomeroLopez-Valcarce:2011:Recent-advances-in-multiantenna-spectrum,
address = {Barcelona, Spain},
author = {G. Vazquez-Vilar and D. Romero and R. L{\'o}pez-Valcarce and D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a and J. Sala},
booktitle = {Int. Work. COST Action IC0902},
month = {{O}ctober},
title = {Recent advances in multiantenna spectrum sensing: complexity, noise uncertainty, and signal rank issues},
year = {2011},
note = {Extended abstract},
}
[Abstract] 183
Experimental evaluation of Interference Alignment under imperfect channel state information(
J. A. García-Naya,
L. Castedo,
Ó. González,
D. Ramírez and I. Santamaría)
Proc. Eur. Signal Process. Conf.,
Barcelona, Spain,
September 2011. [BibTeX]
@inproceedings{Garcia-NayaCastedoGonzalez:2011:Experimental-Evaluation-of-Interference-Alignment,
abstract = {Interference Alignment (IA) has been revealed as one of the most attractive transmission techniques for the K-user in- terference channel. In this work, we employ a multiuser Multiple-Input Multiple-Output (MIMO) testbed to analyze, in realistic indoor scenarios, the impact of channel state information errors on the sum-rate performance of IA. We restrict our study to a 3-user interference network in which each user transmits a single data stream using two transmit and two receive antennas. For this MIMO interference network, only two different IA solutions exist. We also evaluate the performance gain obtained in practice by using the IA solution that maximizes the sum-rate.},
address = {Barcelona, Spain},
author = {J. A. Garc{\'i}a-Naya and L. Castedo and {\'O}. Gonz{\'a}lez and D. Ram{\'i}rez and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {E}ur.\ {S}ignal {P}rocess.\ {C}onf.},
month = {{S}eptember},
title = {Experimental evaluation of {I}nterference {A}lignment under imperfect channel state information},
year = {2011},
}
[Abstract]
Interference Alignment (IA) has been revealed as one of the most attractive transmission techniques for the K-user in- terference channel. In this work, we employ a multiuser Multiple-Input Multiple-Output (MIMO) testbed to analyze, in realistic indoor scenarios, the impact of channel state information errors on the sum-rate performance of IA. We restrict our study to a 3-user interference network in which each user transmits a single data stream using two transmit and two receive antennas. For this MIMO interference network, only two different IA solutions exist. We also evaluate the performance gain obtained in practice by using the IA solution that maximizes the sum-rate. 184
Precoder design and convergence analysis of MIMO systems with Krylov subspace receivers(
Jun Tong,
Peter J. Schreier and Steven R. Weller)
Proc. IEEE Int. Symp. Inform. Theory,
pp. 2914–2918,
August 2011.DOI:10.1109/ISIT.2011.6034110. [BibTeX]
@inproceedings{TongSchreierWeller:2011:Precoder-design-and-convergence-analysis,
abstract = {This paper studies the design and analysis of large multiple-input multiple-output (MIMO) systems with linear precoding and Krylov subspace receivers. We design precoders that can improve performance with low-rank receivers. We then introduce a tool based on potential theory to analyze the convergence behavior of the mean-squared error (MSE). The effectiveness of the proposed precoder and the superexponential convergence of the MSE are demonstrated1.},
author = {Tong, Jun and Schreier, Peter J. and Weller, Steven R.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {S}ymp.\ {I}nform.\ {T}heory},
month = {{A}ugust},
title = {Precoder design and convergence analysis of {MIMO} systems with {Krylov} subspace receivers},
year = {2011},
pages = {2914–2918},
doi = {10.1109/ISIT.2011.6034110},
}
[Abstract]
This paper studies the design and analysis of large multiple-input multiple-output (MIMO) systems with linear precoding and Krylov subspace receivers. We design precoders that can improve performance with low-rank receivers. We then introduce a tool based on potential theory to analyze the convergence behavior of the mean-squared error (MSE). The effectiveness of the proposed precoder and the superexponential convergence of the MSE are demonstrated1. 185
Multi-sensor beamsteering based on the asymptotic likelihood for colored signals(
D. Ramírez,
J. Vía,
I. Santamaría and L. L. Scharf)
Proc. IEEE Work. Stat. Signal Process.,
Nice, France,
June 2011.DOI:10.1109/SSP.2011.5967644. [BibTeX]
@inproceedings{RamirezViaSantamaria:2011:Multi-Sensor-Beamsteering-Based-on-the-Asymptotic,
abstract = {In this work, we derive a maximum likelihood formula for beamsteering in a multi-sensor array. The novelty of the work is that the impinging signal and noises are wide sense stationary (WSS) time series with unknown power spectral densities, unlike in previous work that typically considers white signals. Our approach naturally provides a way of fusing frequency-dependent information to obtain a broadband beamformer. In order to obtain the compressed likelihood, it is necessary to find the maximum likelihood estimates of the unknown parameters. However, this problem turns out to be an ML estimation of a block-Toeplitz matrix, which does not have a closed-form solution. To overcome this problem, we derive the asymptotic likelihood, which is given in the frequency domain. Finally, some simulation results are presented to illustrate the performance of the proposed technique. In these simulations, it is shown that our approach presents the best results.},
address = {Nice, France},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a and L. L. Scharf},
booktitle = {{P}roc.\ {IEEE} {W}ork.\ {S}tat.\ {S}ignal {P}rocess.},
month = {{J}une},
title = {Multi-sensor beamsteering based on the asymptotic likelihood for colored signals},
year = {2011},
doi = {10.1109/SSP.2011.5967644},
}
[Abstract]
In this work, we derive a maximum likelihood formula for beamsteering in a multi-sensor array. The novelty of the work is that the impinging signal and noises are wide sense stationary (WSS) time series with unknown power spectral densities, unlike in previous work that typically considers white signals. Our approach naturally provides a way of fusing frequency-dependent information to obtain a broadband beamformer. In order to obtain the compressed likelihood, it is necessary to find the maximum likelihood estimates of the unknown parameters. However, this problem turns out to be an ML estimation of a block-Toeplitz matrix, which does not have a closed-form solution. To overcome this problem, we derive the asymptotic likelihood, which is given in the frequency domain. Finally, some simulation results are presented to illustrate the performance of the proposed technique. In these simulations, it is shown that our approach presents the best results. 186
Multiantenna detection under noise uncertainty and primary user's spatial structure(
D. Ramírez,
G. Vazquez-Vilar,
R. López-Valcarce,
J. Vía and I. Santamaría)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Prague, Czech Republic,
May 2011.DOI:10.1109/ICASSP.2011.5946275. [BibTeX]
@inproceedings{RamirezVazquez-VilarLopez-Valcarce:2011:Multiantenna-detection-under-noise,
abstract = {Spectrum sensing is a challenging key component of the Cognitive Radio paradigm, since primary signals must be detected in the face of noise uncertainty and at signal-to-noise ratios (SNRs) well below decodability levels. Multiantenna detectors exploit spatial independence of receiver thermal noise to boost detection performance and robustness. Here, we study the problem of detecting Gaussian signals with unknown rank-$P$ spatial covariance matrix when the noise at the receiver is independent across the antennas and with unknown power. A generic diagonal noise covariance matrix is allowed to model calibration uncertainties in the different antenna frontends. We derive the generalized likelihood ratio test (GLRT) for this detection problem. Although, in general, the corresponding statistic must be obtained by numerical means, in the low SNR regime the GLRT does admit a closed form. Numerical simulations show that the proposed asymptotic detector offers good performance even for moderate SNR values.},
address = {Prague, Czech Republic},
author = {D. Ram{\'i}rez and G. Vazquez-Vilar and R. L{\'o}pez-Valcarce and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Multiantenna detection under noise uncertainty and primary user's spatial structure},
year = {2011},
doi = {10.1109/ICASSP.2011.5946275},
}
[Abstract]
Spectrum sensing is a challenging key component of the Cognitive Radio paradigm, since primary signals must be detected in the face of noise uncertainty and at signal-to-noise ratios (SNRs) well below decodability levels. Multiantenna detectors exploit spatial independence of receiver thermal noise to boost detection performance and robustness. Here, we study the problem of detecting Gaussian signals with unknown rank-P spatial covariance matrix when the noise at the receiver is independent across the antennas and with unknown power. A generic diagonal noise covariance matrix is allowed to model calibration uncertainties in the different antenna frontends. We derive the generalized likelihood ratio test (GLRT) for this detection problem. Although, in general, the corresponding statistic must be obtained by numerical means, in the low SNR regime the GLRT does admit a closed form. Numerical simulations show that the proposed asymptotic detector offers good performance even for moderate SNR values. 187
Multiple-channel detection of a Gaussian time series over frequency-flat channels(
D. Ramírez,
J. Vía,
I. Santamaría and L. L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Prague, Czech Republic,
May 2011.DOI:10.1109/ICASSP.2011.5947194. [BibTeX]
@inproceedings{RamirezViaSantamaria:2011:Multiple-Channel-Detection-of-a-Gaussian-Time,
abstract = {This work addresses the problem of deciding whether a set of realizations of a vector-valued time series with unknown temporal correlation are spatially correlated or not. Specifically, the spatial correlation is induced by a colored source over a frequency-flat single-input multiple-output (SIMO) channel distorted by independent and identically distributed noises with temporal correlation. The generalized likelihood ratio test (GLRT) for this detection problem does not have a closed-form expression and we have to resort to numerical optimization techniques. In particular, we apply the successive convex approximations approach which relies on solving a series of convex problems that approximate the original (non-convex) one. The proposed solution resembles a power method for obtaining the dominant eigenvector of a matrix, which changes over iterations. Finally, the performance of the proposed detector is illustrated by means of computer simulations showing a great improvement over previously proposed detectors that do not fully exploit the temporal structure of the source.},
address = {Prague, Czech Republic},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a and L. L. Scharf},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Multiple-channel detection of a {G}aussian time series over frequency-flat channels},
year = {2011},
doi = {10.1109/ICASSP.2011.5947194},
}
[Abstract]
This work addresses the problem of deciding whether a set of realizations of a vector-valued time series with unknown temporal correlation are spatially correlated or not. Specifically, the spatial correlation is induced by a colored source over a frequency-flat single-input multiple-output (SIMO) channel distorted by independent and identically distributed noises with temporal correlation. The generalized likelihood ratio test (GLRT) for this detection problem does not have a closed-form expression and we have to resort to numerical optimization techniques. In particular, we apply the successive convex approximations approach which relies on solving a series of convex problems that approximate the original (non-convex) one. The proposed solution resembles a power method for obtaining the dominant eigenvector of a matrix, which changes over iterations. Finally, the performance of the proposed detector is illustrated by means of computer simulations showing a great improvement over previously proposed detectors that do not fully exploit the temporal structure of the source. 188
Capacity region of the two-way multi-antenna relay channel with analog Tx-Rx beamforming(
Christian Lameiro,
Alfredo Nazábal,
Fouad Gholam,
Javier Vía and Ignacio Santamaría)
Proc. Int. ICST Conf. Mobile Lightweight Wireless Syst.,
Bilbao, Spain,
May 2011.DOI:10.1007/978-3-642-29479-2_1. [BibTeX]
@inproceedings{LameiroNazabalGholam:2011:Capacity-Region-of-the-Two-Way-Multi-Antenna,
abstract = {In this paper we study the multiple-input multiple-output two-way relay channel (MIMO-TWRC) when the nodes use analog beamforming. Following the amplify-and-forward (AF) strategy, the problem consists of finding the transmit and receive beamformers of the nodes and the relay, and the power allocated to each one, that achieve the boundary of the capacity region. We express the optimal node beamformers in terms of the relay beamformers, and show that the capacity region can be efficiently characterized using convex optimization techniques. Numerical examples are provided to illustrate the results of this paper, and to compare the capacity region achieved by analog beamforming against the conventional MIMO schemes that operate at the baseband.},
address = {Bilbao, Spain},
author = {Lameiro, Christian and Naz{\'a}bal, Alfredo and Gholam, Fouad and V{\'i}a, Javier and Santamar{\'i}a, Ignacio},
booktitle = {Proc. Int. ICST Conf. Mobile Lightweight Wireless Syst.},
month = {{M}ay},
title = {Capacity region of the two-way multi-antenna relay channel with analog {Tx-Rx} beamforming},
year = {2011},
doi = {10.1007/978-3-642-29479-2_1},
}
[Abstract]
In this paper we study the multiple-input multiple-output two-way relay channel (MIMO-TWRC) when the nodes use analog beamforming. Following the amplify-and-forward (AF) strategy, the problem consists of finding the transmit and receive beamformers of the nodes and the relay, and the power allocated to each one, that achieve the boundary of the capacity region. We express the optimal node beamformers in terms of the relay beamformers, and show that the capacity region can be efficiently characterized using convex optimization techniques. Numerical examples are provided to illustrate the results of this paper, and to compare the capacity region achieved by analog beamforming against the conventional MIMO schemes that operate at the baseband. 189
Linear precoding for time-varying MIMO channels with low-complexity receivers(
Jun Tong,
Peter J. Schreier,
Steven R. Weller and Louis L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 3092–3095,
May 2011.DOI:10.1109/ICASSP.2011.5946312. [BibTeX]
@inproceedings{TongSchreierWeller:2011:Linear-precoding-for-time-varying-MIMO-c,
abstract = {This paper considers linear precoding for time-varying multiple input multiple-output (MIMO) channels. We show that linear minimum mean-squared error (LMMSE) equalization based on the conjugate gradient (CG) method can result in significantly reduced complexity compared with conventional approaches. This reduction is achieved by incorporating a condition number constraint into the precoder optimization framework, which leads to clustered eigen values of the measurement covariance matrix. The cost is a small increase in MSE compared to the optimal precoder.},
author = {Tong, Jun and Schreier, Peter J. and Weller, Steven R. and Scharf, Louis L.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Linear precoding for time-varying {MIMO} channels with low-complexity receivers},
year = {2011},
pages = {3092–3095},
doi = {10.1109/ICASSP.2011.5946312},
}
[Abstract]
This paper considers linear precoding for time-varying multiple input multiple-output (MIMO) channels. We show that linear minimum mean-squared error (LMMSE) equalization based on the conjugate gradient (CG) method can result in significantly reduced complexity compared with conventional approaches. This reduction is achieved by incorporating a condition number constraint into the precoder optimization framework, which leads to clustered eigen values of the measurement covariance matrix. The cost is a small increase in MSE compared to the optimal precoder. 190
Experimental validation of Interference Alignment Techniques using a Multiuser MIMO testbed(
Ó. González,
D. Ramírez,
I. Santamaría,
J. A. García-Naya and L. Castedo)
Proc. Int. ITG Work. on Smart Antennas,
Aachen, Germany,
February 2011.DOI:10.1109/WSA.2011.5741921. [BibTeX]
@inproceedings{GonzalezRamirezSantamaria:2011:Experimental-Validation-of-Interference-Alignment,
abstract = {Hardware platforms and testbeds are an essential tool to evaluate, in realistic scenarios, the performance of wireless communications systems. In this work we present a multiuser Multiple-Input Multiple-Output (MIMO) testbed made up of 6 nodes, each one with 4 antennas, which allows us to evaluate Interference Alignment (IA) techniques in indoor scenarios. We specifically study the performance of IA for the 3-user interference channel in the 5 GHz band. Our analysis identifies the main practical issues that potentially degrade the IA performance such as channel estimation errors or collinearity between the desired signal and interference subspaces.},
address = {Aachen, Germany},
author = {{\'O}. Gonz{\'a}lez and D. Ram{\'i}rez and I. Santamar{\'i}a and J. A. Garc{\'i}a-Naya and L. Castedo},
booktitle = {Proc.\ Int.\ ITG Work.\ on Smart Antennas},
month = {{F}ebruary},
title = {Experimental validation of {I}nterference {A}lignment Techniques using a Multiuser {MIMO} testbed},
year = {2011},
doi = {10.1109/WSA.2011.5741921},
}
[Abstract]
Hardware platforms and testbeds are an essential tool to evaluate, in realistic scenarios, the performance of wireless communications systems. In this work we present a multiuser Multiple-Input Multiple-Output (MIMO) testbed made up of 6 nodes, each one with 4 antennas, which allows us to evaluate Interference Alignment (IA) techniques in indoor scenarios. We specifically study the performance of IA for the 3-user interference channel in the 5 GHz band. Our analysis identifies the main practical issues that potentially degrade the IA performance such as channel estimation errors or collinearity between the desired signal and interference subspaces. 191
Multiantenna spectrum sensing: the case of wideband rank-one primary signals(
D. Ramírez,
J. Vía and I. Santamaría)
Proc. IEEE Sensor Array and Multichannel Signal Process. Work.,
Israel,
October 2010.DOI:10.1109/SAM.2010.5606502. [BibTeX]
@inproceedings{RamirezViaSantamaria:2010:Multiantenna-spectrum-sensing:-The-case,
abstract = {One of the key problems in cognitive radio (CR) is the detection of primary activity in order to determine which parts of the spectrum are available for opportunistic access. In this work, we present a new multiantenna detector which fully exploits the spatial and temporal structure of the signals. In particular, we derive the generalized likelihood ratio test (GLRT) for the problem of detecting a wideband rank-one signal under spatially uncorrelated noise with equal or different power spectral densities. In order to simplify the maximum likelihood (ML) estimation of the unknown parameters, we use the asymptotic likelihood in the frequency domain. Interestingly, for noises with different distributions and under a low SNR approximation, the GLRT is obtained as a function of the largest eigenvalue of the spectral coherence matrix. Finally, the performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages over previously proposed approaches.},
address = {Israel},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {S}ensor {A}rray and {M}ultichannel {S}ignal {P}rocess. {W}ork.},
month = {{O}ctober},
title = {Multiantenna spectrum sensing: the case of wideband rank-one primary signals},
year = {2010},
doi = {10.1109/SAM.2010.5606502},
}
[Abstract]
One of the key problems in cognitive radio (CR) is the detection of primary activity in order to determine which parts of the spectrum are available for opportunistic access. In this work, we present a new multiantenna detector which fully exploits the spatial and temporal structure of the signals. In particular, we derive the generalized likelihood ratio test (GLRT) for the problem of detecting a wideband rank-one signal under spatially uncorrelated noise with equal or different power spectral densities. In order to simplify the maximum likelihood (ML) estimation of the unknown parameters, we use the asymptotic likelihood in the frequency domain. Interestingly, for noises with different distributions and under a low SNR approximation, the GLRT is obtained as a function of the largest eigenvalue of the spectral coherence matrix. Finally, the performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages over previously proposed approaches. 192
Improperness measures for quaternion random vectors(
J. Vía,
D. Ramírez,
I. Santamaría and L. Vielva)
Proc. IEEE Int. Work. Machine Learning for Signal Process.,
Finland,
August 2010.DOI:10.1109/MLSP.2010.5589225. [BibTeX]
@inproceedings{ViaRamirezSantamaria:2010:Improperness-Measures-for-Quaternion-Random,
abstract = {It has been recently proved that the two main kinds of quaternion improperness require two different kinds of widely linear process- ing. In this work, we show that these definitions satisfy some im- portant properties, which include the invariance to quaternion lin- ear transformations and right Clifford translations, as well as some clear connections with the case of proper complex vectors. More- over, we introduce a new kind of quaternion properness, which clearly relates the two previous definitions, and propose three mea- sures for the degree of improperness of a quaternion vector. The proposed measures are based on the Kullback-Leibler divergence between two zero-mean quaternion Gaussian distributions, one of them with the actual augmented covariance matrix, and the other with its closest proper version. These measures allow us to quan- tify the entropy loss due to the improperness of the quaternion vec- tor, and they admit an intuitive geometrical interpretation based on Kullback-Leibler projections onto sets of proper augmented co- variance matrices.},
address = {Finland},
author = {J. V{\'i}a and D. Ram{\'i}rez and I. Santamar{\'i}a and L. Vielva},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {W}ork.\ Machine Learning for Signal Process.},
month = {{A}ugust},
title = {Improperness measures for quaternion random vectors},
year = {2010},
doi = {10.1109/MLSP.2010.5589225},
}
[Abstract]
It has been recently proved that the two main kinds of quaternion improperness require two different kinds of widely linear process- ing. In this work, we show that these definitions satisfy some im- portant properties, which include the invariance to quaternion lin- ear transformations and right Clifford translations, as well as some clear connections with the case of proper complex vectors. More- over, we introduce a new kind of quaternion properness, which clearly relates the two previous definitions, and propose three mea- sures for the degree of improperness of a quaternion vector. The proposed measures are based on the Kullback-Leibler divergence between two zero-mean quaternion Gaussian distributions, one of them with the actual augmented covariance matrix, and the other with its closest proper version. These measures allow us to quan- tify the entropy loss due to the improperness of the quaternion vec- tor, and they admit an intuitive geometrical interpretation based on Kullback-Leibler projections onto sets of proper augmented co- variance matrices. 193
Capacity region of the multiantenna gaussian broadcast channel with analog TX-RX beamforming(
Ignacio Santamaría,
Javier Vía,
Alfredo Nazábal and Christian Lameiro)
Proc. Int. ICST Conf. Comm. and Networking in China,
Beijing, China,
August 2010. [BibTeX]
@inproceedings{SantamariaViaNazabal:2010:Capacity-region-of-the-multiantenna-Gaussian,
abstract = {In this paper we characterize the capacity boundary of the two-user multiple-input multiple-output (MIMO) broadcast channel (BC) when the multiantenna terminals use analog beamforming at both sides of the link. Basically, the problem reduces to finding the optimal transmit direction and the optimal power allocation between users to operate at any point on the boundary. We show that both optimization problems can be solved in closed form. First, exploiting the fact that any Pareto optimal pair of rates must also be Pareto optimal of a convex region defined by the channel energies, the optimal transmit direction is shown to be the principal eigenvector of a matrix. Second, the optimal power allocation is obtained by exploiting again the Pareto optimality of the sought pair of rates. Although this paper focuses on the BC, the obtained results also serve to characterize the dual multiple-access channel (MAC). Moreover, this explicit characterization of the boundary can be extended to a $K$-user system for $K>2$. Numerical examples are provided to illustrate the results of the paper, and to show the enlargement of the capacity region achieved by analog beamforming in comparison to a single-input single-output (SISO) BC.},
address = {Beijing, China},
author = {Santamar{\'i}a, Ignacio and V{\'i}a, Javier and Naz{\'a}bal, Alfredo and Lameiro, Christian},
booktitle = {Proc. Int. ICST Conf. Comm. and Networking in China},
month = {{A}ugust},
title = {Capacity region of the multiantenna gaussian broadcast channel with analog {TX-RX} beamforming},
year = {2010},
}
[Abstract]
In this paper we characterize the capacity boundary of the two-user multiple-input multiple-output (MIMO) broadcast channel (BC) when the multiantenna terminals use analog beamforming at both sides of the link. Basically, the problem reduces to finding the optimal transmit direction and the optimal power allocation between users to operate at any point on the boundary. We show that both optimization problems can be solved in closed form. First, exploiting the fact that any Pareto optimal pair of rates must also be Pareto optimal of a convex region defined by the channel energies, the optimal transmit direction is shown to be the principal eigenvector of a matrix. Second, the optimal power allocation is obtained by exploiting again the Pareto optimality of the sought pair of rates. Although this paper focuses on the BC, the obtained results also serve to characterize the dual multiple-access channel (MAC). Moreover, this explicit characterization of the boundary can be extended to a K-user system for K>2. Numerical examples are provided to illustrate the results of the paper, and to show the enlargement of the capacity region achieved by analog beamforming in comparison to a single-input single-output (SISO) BC. 194
Multiantenna spectrum sensing: detection of spatial correlation among time-series with unknown spectra(
D. Ramírez,
J. Vía,
I. Santamaría,
R. López-Valcarce and L. L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Dallas, USA,
March 2010.DOI:10.1109/ICASSP.2010.5496151. [BibTeX]
@inproceedings{RamirezViaSantamaria:2010:Multiantenna-Spectrum-Sensing:-Detection,
abstract = {One of the key problems in cognitive radio (CR) is the detection of primary activity in order to determine which parts of the spectrum are available for opportunistic access. This detection task is challenging, since the wireless environment often results in very low SNR conditions. Moreover, calibration errors and imperfect analog components at the CR spectral monitor result in uncertainties in the noise spectrum, making the problem more difficult. In this work, we present a new multiantenna detector which is based on the fact that the observation noise processes are spatially uncorrelated, whereas any primary signal present should result inspatial correlation. In particular, we derive the generalized likelihood ratio test (GLRT) for this problem, which is given by the quotient between the determinant of the sample covariance matrix and the determinant of its block-diagonal version. For stationary processes the GLRT tends asymptotically to the integral of the logarithm of the Hadamard ratio of the estimated power spectral density matrix. Additionally, we present an approximation of the frequency domain detector in the low SNR regime, which results in computational savings. The performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages over existing detectors.},
address = {Dallas, USA},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a and R. L{\'o}pez-Valcarce and L. L. Scharf},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Multiantenna spectrum sensing: detection of spatial correlation among time-series with unknown spectra},
year = {2010},
doi = {10.1109/ICASSP.2010.5496151},
}
[Abstract]
One of the key problems in cognitive radio (CR) is the detection of primary activity in order to determine which parts of the spectrum are available for opportunistic access. This detection task is challenging, since the wireless environment often results in very low SNR conditions. Moreover, calibration errors and imperfect analog components at the CR spectral monitor result in uncertainties in the noise spectrum, making the problem more difficult. In this work, we present a new multiantenna detector which is based on the fact that the observation noise processes are spatially uncorrelated, whereas any primary signal present should result inspatial correlation. In particular, we derive the generalized likelihood ratio test (GLRT) for this problem, which is given by the quotient between the determinant of the sample covariance matrix and the determinant of its block-diagonal version. For stationary processes the GLRT tends asymptotically to the integral of the logarithm of the Hadamard ratio of the estimated power spectral density matrix. Additionally, we present an approximation of the frequency domain detector in the low SNR regime, which results in computational savings. The performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages over existing detectors. 195
Widely and semi-widely linear processing of quaternion vectors(
J. Vía,
D. Ramírez,
I. Santamaría and L. Vielva)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Dallas, USA,
March 2010.DOI:10.1109/ICASSP.2010.5495787. [BibTeX]
@inproceedings{ViaRamirezSantamaria:2010:Widely-and-semi-widely-linear-processing,
abstract = {In this paper the two main definitions of quaternion properness (or second order circularity) are reviewed, showing their connection with the structure of the optimal quaternion linear processing. Specifically, we present a rigorous generalization of the most common multivariate statistical analysis techniques to the case of quaternion vectors, and show that the different kinds of quaternion improperness require different kinds of widely linear processing. In general, the optimal linear processing is \emph{full-widely linear}, which requires the joint processing of the quaternion vector and its involutions over three pure unit quaternions. However, in the case of jointly $\mathbb{Q}$-proper and $\mathbb{C}^{\eta}$-proper vectors, the optimal processing reduces, respectively, to the \emph{conventional} and \emph{semi-widely linear processing}, with the latter only requiring to operate on the quaternion vector and its involution over the pure unit quaternion $\eta$. Finally, a simulation example poses some interesting questions for future research.},
address = {Dallas, USA},
author = {J. V{\'i}a and D. Ram{\'i}rez and I. Santamar{\'i}a and L. Vielva},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}arch},
title = {Widely and semi-widely linear processing of quaternion vectors},
year = {2010},
doi = {10.1109/ICASSP.2010.5495787},
}
[Abstract]
In this paper the two main definitions of quaternion properness (or second order circularity) are reviewed, showing their connection with the structure of the optimal quaternion linear processing. Specifically, we present a rigorous generalization of the most common multivariate statistical analysis techniques to the case of quaternion vectors, and show that the different kinds of quaternion improperness require different kinds of widely linear processing. In general, the optimal linear processing is full-widely linear, which requires the joint processing of the quaternion vector and its involutions over three pure unit quaternions. However, in the case of jointly mathbbQ-proper and mathbbC^eta-proper vectors, the optimal processing reduces, respectively, to the conventional and semi-widely linear processing, with the latter only requiring to operate on the quaternion vector and its involution over the pure unit quaternion eta. Finally, a simulation example poses some interesting questions for future research. 196
Coherent fusion of information for optimal detection in sensor networks(
D. Ramírez,
J. Vía and I. Santamaría)
Proc. IEEE Work. Stat. Signal Process.,
Cardiff, UK,
September 2009.DOI:10.1109/SSP.2009.5278473. [BibTeX]
@inproceedings{RamirezViaSantamaria:2009:Coherent-Fusion-of-Information-for-Optimal,
abstract = {In this work, we consider the problem of centralized detection in wireless sensor networks when the sensors transmit coherently through a multiple access channel. We derive the optimal weighting at each sensor that maximizes the error exponent. Firstly, the noiseless case is considered and a closed-form solution to the problem is found. Secondly, we generalize the formulation to consider additive noise at the fusion center. For the noisy case, we propose a suboptimal approach which allows us to find a closed-form solution. Interestingly, the proposed approaches reduce to the extraction of a normalized eigenvector of a generalized eigenvalue problem. The performance of the proposed scheme is illustrated by means of numerical results, showing that the suboptimal approach has a similar performance to that of the optimal one; and that the proposed scheme outperforms other techniques, such as orthogonal transmissions or the maximization of the signal-to-noise ratio.},
address = {Cardiff, UK},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {W}ork.\ {S}tat.\ {S}ignal {P}rocess.},
month = {{S}eptember},
title = {Coherent fusion of information for optimal detection in sensor networks},
year = {2009},
doi = {10.1109/SSP.2009.5278473},
}
[Abstract]
In this work, we consider the problem of centralized detection in wireless sensor networks when the sensors transmit coherently through a multiple access channel. We derive the optimal weighting at each sensor that maximizes the error exponent. Firstly, the noiseless case is considered and a closed-form solution to the problem is found. Secondly, we generalize the formulation to consider additive noise at the fusion center. For the noisy case, we propose a suboptimal approach which allows us to find a closed-form solution. Interestingly, the proposed approaches reduce to the extraction of a normalized eigenvector of a generalized eigenvalue problem. The performance of the proposed scheme is illustrated by means of numerical results, showing that the suboptimal approach has a similar performance to that of the optimal one; and that the proposed scheme outperforms other techniques, such as orthogonal transmissions or the maximization of the signal-to-noise ratio. 197
Entropy and Kullback-Leibler divergence estimation based on Szegö's theorem(
D. Ramírez,
J. Vía,
I. Santamaría and P. Crespo)
Proc. Eur. Signal Process. Conf.,
Glasgow, Scotland,
August 2009. [BibTeX]
@inproceedings{RamirezViaSantamaria:2009:Entropy-and-Kullback-Leibler-divergence-estimation,
abstract = {In this work, a new technique for the estimation of the Shannon's entropy and the Kullback-Leibler (KL) divergence for one dimensional data is presented. The estimator is based on the Szeg\"o's theorem for sequences of Toeplitz matrices, which deals with the asymptotic behavior of the eigenvalues of those matrices, and the analogy between a probability density function (PDF) and a power spectral density (PSD), which allows us to estimate a PDF of bounded support using the well-known spectral estimation techniques. Specifically, an AR model is used for the PDF PSD estimation, and the entropy is easily estimated as a function of the eigenvalues of the autocorrelation Toeplitz matrix. The performance of the Szeg\"o's estimators is illustrated by means of Monte Carlo simulations and compared with previously proposed alternatives, showing a good performance.},
address = {Glasgow, Scotland},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a and P. Crespo},
booktitle = {{P}roc.\ {E}ur.\ {S}ignal {P}rocess.\ {C}onf.},
month = {{A}ugust},
title = {Entropy and {K}ullback-{L}eibler divergence estimation based on {S}zeg\"o's theorem},
year = {2009},
}
[Abstract]
In this work, a new technique for the estimation of the Shannon's entropy and the Kullback-Leibler (KL) divergence for one dimensional data is presented. The estimator is based on the Szeg"o's theorem for sequences of Toeplitz matrices, which deals with the asymptotic behavior of the eigenvalues of those matrices, and the analogy between a probability density function (PDF) and a power spectral density (PSD), which allows us to estimate a PDF of bounded support using the well-known spectral estimation techniques. Specifically, an AR model is used for the PDF PSD estimation, and the entropy is easily estimated as a function of the eigenvalues of the autocorrelation Toeplitz matrix. The performance of the Szeg"o's estimators is illustrated by means of Monte Carlo simulations and compared with previously proposed alternatives, showing a good performance. 198
The Wiener filter for locally stationary stochastic processes is rarely locally stationary
(Patrik Wahlberg and Peter J. Schreier)
Proc. 17th European Signal Process. Conf., pp. 2465–2469, August 2009. [BibTeX]
@inproceedings{WahlbergSchreier:2009:The-Wiener-filter-for-locally-stationary,
abstract = {The Wiener filter (i.e., linear minimum mean squared error filter) for wide-sense stationary stochastic processes is translation-invariant, i.e., its impulse response, like the covariance function, is only a function of the time-shift. We investigate whether there is a generalization of this result to continuous-time stochastic processes that are locally stationary in Silverman's sense: Is the optimal filter for locally stationary processes locally stationary itself? The answer is surprisingly negative: Even though the optimal filter can be locally stationary in special cases, it rarely is, even when the covariance functions have Gaussian shape.},
author = {Wahlberg, Patrik and Schreier, Peter J.},
booktitle = {{P}roc.\ 17th\ {E}uropean {S}ignal {P}rocess.\ {C}onf.},
month = {{A}ugust},
title = {The {Wiener} filter for locally stationary stochastic processes is rarely locally stationary},
year = {2009},
pages = {2465–2469},
}
[Abstract]
The Wiener filter (i.e., linear minimum mean squared error filter) for wide-sense stationary stochastic processes is translation-invariant, i.e., its impulse response, like the covariance function, is only a function of the time-shift. We investigate whether there is a generalization of this result to continuous-time stochastic processes that are locally stationary in Silverman's sense: Is the optimal filter for locally stationary processes locally stationary itself? The answer is surprisingly negative: Even though the optimal filter can be locally stationary in special cases, it rarely is, even when the covariance functions have Gaussian shape.
199
On ICA of improper and noncircular sources(
Peter J. Schreier,
Tülay Adali and Louis L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 3561–3564,
April 2009.DOI:10.1109/ICASSP.2009.4960395. [BibTeX]
@inproceedings{SchreierAdaliScharf:2009:On-ICA-of-improper-and-noncircular-sourc,
abstract = {We provide a review of independent component analysis (ICA) for complex-valued improper and noncircular random sources. An improper random signal is correlated with its complex conjugate, and a noncircular random signal has a rotationally variant probability distribution. We present methods for ICA using second-order statistics, and higher-order statistics. For ICA based on second-order statistics, we emphasize the key role played by the circularity coefficients, which are the canonical correlations between the source and the complex conjugate. For ICA based on higher-order statistics, we show how to extend algorithms for real-valued ICA to the complex domain using Wirtinger calculus.},
author = {Schreier, Peter J. and Adali, T{\"u}lay and Scharf, Louis L.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {On {ICA} of improper and noncircular sources},
year = {2009},
pages = {3561–3564},
doi = {10.1109/ICASSP.2009.4960395},
}
[Abstract]
We provide a review of independent component analysis (ICA) for complex-valued improper and noncircular random sources. An improper random signal is correlated with its complex conjugate, and a noncircular random signal has a rotationally variant probability distribution. We present methods for ICA using second-order statistics, and higher-order statistics. For ICA based on second-order statistics, we emphasize the key role played by the circularity coefficients, which are the canonical correlations between the source and the complex conjugate. For ICA based on higher-order statistics, we show how to extend algorithms for real-valued ICA to the complex domain using Wirtinger calculus. 200
Impact of signaling schemes on iterative linear minimum-mean-square-error detection(
Li Ping,
Jun Tong,
Xiaojun Yuan and Qinghua Guo)
Proc. IEEE Global Telecomm. Conf.,
pp. 1–5,
December 2008.DOI:10.1109/GLOCOM.2008.ECP.665. [BibTeX]
@inproceedings{PingTongYuan:2008:Impact-of-signaling-schemes-on-iterative,
abstract = {In this paper, we study the iterative detection problem for a coded system with multi-ary modulation. We show that, with iterative linear minimum-mean-square-error (LMMSE) detection, superposition coded modulation (SCM) can provide performance superior to that with other traditional signaling schemes used in trellis coded modulation (TCM) and bit-interleaved coded modulation (BICM). This finding provides a useful guideline for system design considering inter-symbol interference (ISI) and other forms of interference. Simulation results are provided to illustrate the efficiency of the iterative LMMSE detection with different signaling schemes.},
author = {Ping, Li and Tong, Jun and Yuan, Xiaojun and Guo, Qinghua},
booktitle = {{P}roc.\ {IEEE} {G}lobal {T}elecomm.\ {C}onf.},
month = {{D}ecember},
title = {Impact of signaling schemes on iterative linear minimum-mean-square-error detection},
year = {2008},
pages = {1–5},
doi = {10.1109/GLOCOM.2008.ECP.665},
}
[Abstract]
In this paper, we study the iterative detection problem for a coded system with multi-ary modulation. We show that, with iterative linear minimum-mean-square-error (LMMSE) detection, superposition coded modulation (SCM) can provide performance superior to that with other traditional signaling schemes used in trellis coded modulation (TCM) and bit-interleaved coded modulation (BICM). This finding provides a useful guideline for system design considering inter-symbol interference (ISI) and other forms of interference. Simulation results are provided to illustrate the efficiency of the iterative LMMSE detection with different signaling schemes. 201
Iterative detection techniques for clipped OFDM systems(
Jun Tong and Li Ping)
Proc. IEEE Global Telecomm. Conf.,
pp. 1–5,
December 2008.DOI:10.1109/GLOCOM.2008.ECP.225. [BibTeX]
@inproceedings{TongPing:2008:Iterative-detection-techniques-for-clipp,
abstract = {This paper studies orthogonal frequency-division multiplexing (OFDM) systems employing coded modulation. Clipping is applied to reduce the peak-to-average-power-ratio (PAPR) of the transmit signal. A soft compensation method is proposed to combat the clipping effect. It is shown that the proposed method can outperform conventional clipping effect mitigation methods. The impact of signaling schemes of the coded modulation on system performance is investigated. The average variance analysis and numerical results demonstrate that superposition coded modulation (SCM) together with the proposed detection technique provides a simple and efficient solution to clipped OFDM transmission.},
author = {Tong, Jun and Ping, Li},
booktitle = {{P}roc.\ {IEEE} {G}lobal {T}elecomm.\ {C}onf.},
month = {{D}ecember},
title = {Iterative detection techniques for clipped {OFDM} systems},
year = {2008},
pages = {1–5},
doi = {10.1109/GLOCOM.2008.ECP.225},
}
[Abstract]
This paper studies orthogonal frequency-division multiplexing (OFDM) systems employing coded modulation. Clipping is applied to reduce the peak-to-average-power-ratio (PAPR) of the transmit signal. A soft compensation method is proposed to combat the clipping effect. It is shown that the proposed method can outperform conventional clipping effect mitigation methods. The impact of signaling schemes of the coded modulation on system performance is investigated. The average variance analysis and numerical results demonstrate that superposition coded modulation (SCM) together with the proposed detection technique provides a simple and efficient solution to clipped OFDM transmission. 202
Performance analysis of multi-ary systems with iterative linear minimum-mean-square-error detection(
Li Ping,
Jun Tong,
Xiaojun Yuan and Qinghua Guo)
5th Int. Symp. Turbo Codes & Rel. Top.,
pp. 192–197,
September 2008.DOI:10.1109/TURBOCODING.2008.4658696. [BibTeX]
@inproceedings{PingTongYuan:2008:Performance-analysis-of-multi-ary-system,
abstract = {This paper is concerned with coded multi-ary systems over linear channels. Based on a semi-analytical evolution technique, the impact of signaling schemes on the performance of low-cost iterative linear minimum-mean-square-error (LMMSE) detection is studied. It is shown that superposition coded modulation (SCM) maximizes the output signal-to-noise ratio (SNR) of LMMSE detectors. Consequently, SCM may potentially outperform other conventional signaling schemes when LMMSE detectors are used. Numerical examples are provided to verify the theoretical analysis.},
author = {Ping, Li and Tong, Jun and Yuan, Xiaojun and Guo,Qinghua},
booktitle = {5th\ {I}nt.\ {S}ymp.\ {T}urbo {C}odes \& {R}el.\ {T}op.},
month = {{S}eptember},
title = {Performance analysis of multi-ary systems with iterative linear minimum-mean-square-error detection},
year = {2008},
pages = {192–197},
doi = {10.1109/TURBOCODING.2008.4658696},
}
[Abstract]
This paper is concerned with coded multi-ary systems over linear channels. Based on a semi-analytical evolution technique, the impact of signaling schemes on the performance of low-cost iterative linear minimum-mean-square-error (LMMSE) detection is studied. It is shown that superposition coded modulation (SCM) maximizes the output signal-to-noise ratio (SNR) of LMMSE detectors. Consequently, SCM may potentially outperform other conventional signaling schemes when LMMSE detectors are used. Numerical examples are provided to verify the theoretical analysis. 203
Optimal MIMO transmission schemes with adaptive antenna combining in the RF path(
I. Santamaría,
V. Elvira,
J. Vía,
D. Ramírez,
J. Pérez,
J. Ibáñez,
R. Eickhoff and F. Ellinger)
Proc. Eur. Signal Process. Conf.,
Lausanne, Switzerland,
August 2008. [BibTeX]
@inproceedings{SantamariaElviraVia:2008:Optimal-MIMO-transmission-schemes,
abstract = {In this paper we study space-time coding schemes for a novel MIMO transceiver which performs adaptive signal combining in radio-frequency (RF). The limitations of the RF circuitry make necessary to develop specific designs for this architecture. For instance, the space and time encoders must operate separately (the former works in the RF domain and the latter works in baseband), and at different time scales: the spatial encoder or RF beamformer must remain fixed dur- ing the transmission of a probably large number of symbols, whereas the time-encoder can work at the symbol rate. We show in the paper that although the multiplexing gain of the system is limited to one, we are still able to achieve the full spatial diversity of the MIMO channel as well as to increase the received signal-to-noise ratio through array gain. Specifically, when perfect channel state information (CSI) is available only at the receiver we propose to use a scheme referred to as orthogonal beam division multiplexing (OBDM). With this scheme the symbols are time-precoded with a unitary discrete Fourier transform (DFT) matrix, then they are successively transmitted through orthogonal direc- tions and, finally, we use a receiver comprising maximal ra- tio combining (MRC) followed by a minimum mean-square error (MMSE) decoder. The performance of the proposed techniques in terms of outage capacity and bit error rate is illustrated by means of several simulations examples.},
address = {Lausanne, Switzerland},
author = {I. Santamar{\'i}a and V. Elvira and J. V{\'i}a and D. Ram{\'i}rez and J. P{\'e}rez and J. Ib{\'a}{\~n}ez and R. Eickhoff and F. Ellinger},
booktitle = {{P}roc.\ {E}ur.\ {S}ignal {P}rocess.\ {C}onf.},
month = {{A}ugust},
title = {Optimal {MIMO} transmission schemes with adaptive antenna combining in the {RF} path},
year = {2008},
}
[Abstract]
In this paper we study space-time coding schemes for a novel MIMO transceiver which performs adaptive signal combining in radio-frequency (RF). The limitations of the RF circuitry make necessary to develop specific designs for this architecture. For instance, the space and time encoders must operate separately (the former works in the RF domain and the latter works in baseband), and at different time scales: the spatial encoder or RF beamformer must remain fixed dur- ing the transmission of a probably large number of symbols, whereas the time-encoder can work at the symbol rate. We show in the paper that although the multiplexing gain of the system is limited to one, we are still able to achieve the full spatial diversity of the MIMO channel as well as to increase the received signal-to-noise ratio through array gain. Specifically, when perfect channel state information (CSI) is available only at the receiver we propose to use a scheme referred to as orthogonal beam division multiplexing (OBDM). With this scheme the symbols are time-precoded with a unitary discrete Fourier transform (DFT) matrix, then they are successively transmitted through orthogonal direc- tions and, finally, we use a receiver comprising maximal ra- tio combining (MRC) followed by a minimum mean-square error (MMSE) decoder. The performance of the proposed techniques in terms of outage capacity and bit error rate is illustrated by means of several simulations examples. 204
Performance analysis of OFDM-IDMA systems with peak-power limitation(
Jun Tong,
Qinghua Guo and Li Ping)
IEEE 10th Int. Symp. Spread Spectrum Techn. & Appl.,
pp. 555–559,
August 2008.DOI:10.1109/ISSSTA.2008.109. [BibTeX]
@inproceedings{TongGuoPing:2008:Performance-analysis-of-OFDM-IDMA-system,
abstract = {This paper is concerned with orthogonal frequencydivision multiplexing interleave-division multiple-access (OFDMIDMA) systems over frequency-selective fading channels. Deliberate clipping is applied to reduce the peak-to-average power ratio (PAPR) of each user's transmitted signal. An iterative multiuser detection (MUD) technique is developed to recover the performance loss due to clipping. A semi-analytical signal-to-noise ratio (SNR) evolution technique is proposed, which can provide quick and accurate prediction of the iterative MUD performance. Numerical results show that the performance of OFDM-IDMA is not sensitive to the frequency selectivity of channels, and OFDM-IDMA is more power-efficient than other alternative multi-carrier transmission techniques},
author = {Tong, Jun and Guo, Qinghua and Ping, Li},
booktitle = {{IEEE} 10th\ {I}nt.\ {S}ymp.\ {S}pread {S}pectrum {T}echn.\ \& {A}ppl.},
month = {{A}ugust},
title = {Performance analysis of {OFDM-IDMA} systems with peak-power limitation},
year = {2008},
pages = {555–559},
doi = {10.1109/ISSSTA.2008.109},
}
[Abstract]
This paper is concerned with orthogonal frequencydivision multiplexing interleave-division multiple-access (OFDMIDMA) systems over frequency-selective fading channels. Deliberate clipping is applied to reduce the peak-to-average power ratio (PAPR) of each user's transmitted signal. An iterative multiuser detection (MUD) technique is developed to recover the performance loss due to clipping. A semi-analytical signal-to-noise ratio (SNR) evolution technique is proposed, which can provide quick and accurate prediction of the iterative MUD performance. Numerical results show that the performance of OFDM-IDMA is not sensitive to the frequency selectivity of channels, and OFDM-IDMA is more power-efficient than other alternative multi-carrier transmission techniques 205
A time-frequency formula for LMMSE filters for nonstationary underspread continuous-time stochastic processes
(Patrik Wahlberg and Peter J. Schreier)
Proc. 16th European Signal Process. Conf., August 2008. [BibTeX]
@inproceedings{WahlbergSchreier:2008:A-time-frequency-formula-for-LMMSE-filte,
abstract = {We study linear minimum mean square error (LMMSE) filters for estimating a nonstationary second-order continuous-time stochastic process from a noisy observation. The equation for the optimal filter is treated in the Weyl symbol domain, and the involved Weyl symbols are assumed to belong to certain modulation spaces. By discretizing this equation using a Gabor frame we transform it into a matrix equation and obtain a formula for the filter by matrix inversion. The inverse matrix has off-diagonal decay at a rate that increases the more underspread the process is.},
author = {Wahlberg, Patrik and Schreier, Peter J.},
booktitle = {{P}roc.\ 16th\ {E}uropean {S}ignal {P}rocess.\ {C}onf.},
month = {{A}ugust},
title = {A time-frequency formula for {LMMSE} filters for nonstationary underspread continuous-time stochastic processes},
year = {2008},
}
[Abstract]
We study linear minimum mean square error (LMMSE) filters for estimating a nonstationary second-order continuous-time stochastic process from a noisy observation. The equation for the optimal filter is treated in the Weyl symbol domain, and the involved Weyl symbols are assumed to belong to certain modulation spaces. By discretizing this equation using a Gabor frame we transform it into a matrix equation and obtain a formula for the filter by matrix inversion. The inverse matrix has off-diagonal decay at a rate that increases the more underspread the process is.
206
Multiple-channel signal detection using the generalized coherence spectrum(
D. Ramírez,
J. Vía and I. Santamaría)
Proc. IAPR Work. Cognitive Information Process.,
Santorini, Greece,
June 2008. [BibTeX]
@inproceedings{RamirezViaSantamaria:2008:Multiple-Channel-Signal-Detection-using,
abstract = {Recently, a generalization of the magnitude squared coherence (MSC) spectrum for more than two random processes has been proposed. The generalized MSC (GMSC) spectrum definition, which is based on the largest eigenvalue of a matrix containing all the pairwise complex coherence spectra, provides a frequency-dependent measure of the linear relationship among several stationary random processes. Moreover, it can be easily estimated by solving a generalized eigenvalue problem. In this paper we apply the GMSC spectrum for detecting the presence of a common signal from a set of linearly distorted and noisy observations. Specifically, the new statistic for the multiple-channel detection problem is the integral of the square root of the GMSC, which can be estimated as the sum of the $P$ largest generalized canonical correlations (typically $P=1$ is enough in practice). Unlike previous approaches, the new statistic implicitly takes into account the spectral characteristics of the signal to be detected (e.g., its bandwidth). Finally, the performance of the proposed detector is compared in terms of its receiver operating characteristic (ROC) curve with the generalized coherence (GC) showing a clear improvement in most scenarios.},
address = {Santorini, Greece},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {Proc.\ {IAPR} Work.\ Cognitive Information Process.},
month = {{J}une},
title = {Multiple-channel signal detection using the generalized coherence spectrum},
year = {2008},
}
[Abstract]
Recently, a generalization of the magnitude squared coherence (MSC) spectrum for more than two random processes has been proposed. The generalized MSC (GMSC) spectrum definition, which is based on the largest eigenvalue of a matrix containing all the pairwise complex coherence spectra, provides a frequency-dependent measure of the linear relationship among several stationary random processes. Moreover, it can be easily estimated by solving a generalized eigenvalue problem. In this paper we apply the GMSC spectrum for detecting the presence of a common signal from a set of linearly distorted and noisy observations. Specifically, the new statistic for the multiple-channel detection problem is the integral of the square root of the GMSC, which can be estimated as the sum of the P largest generalized canonical correlations (typically P=1 is enough in practice). Unlike previous approaches, the new statistic implicitly takes into account the spectral characteristics of the signal to be detected (e.g., its bandwidth). Finally, the performance of the proposed detector is compared in terms of its receiver operating characteristic (ROC) curve with the generalized coherence (GC) showing a clear improvement in most scenarios. 207
A generalization of the magnitude squared coherence spectrum for more than two signals: definition, properties and estimation(
D. Ramírez,
J. Vía and I. Santamaría)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Las Vegas, USA,
April 2008.DOI:10.1109/ICASSP.2008.4518473. [BibTeX]
@inproceedings{RamirezViaSantamaria:2008:A-generalization-of-the-magnitude-squared-coherence,
abstract = {The coherence spectrum is a well-known measure of the linear statistical relationship between two time series. In this paper, we extend this concept to several processes and define the generalized magnitude squared coherence (GMSC) spectrum as a function of the largest eigenvalue of a matrix containing all the pairwise complex coherence spectra. The GMSC is bounded between zero and one, and attains its maximum when all the processes are perfectly correlated at a given frequency. Furthermore, three different GMSC spectrum estimators, extending those previously proposed for the MSC of two processes, are presented. Specifically, we compare the Welch method, the minimum variance distortionless response (MVDR) estimator and a new estimator based on canonical correlation analysis (CCA).},
address = {Las Vegas, USA},
author = {D. Ram{\'i}rez and J. V{\'i}a and I. Santamar{\'i}a},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {A generalization of the magnitude squared coherence spectrum for more than two signals: definition, properties and estimation},
year = {2008},
doi = {10.1109/ICASSP.2008.4518473},
}
[Abstract]
The coherence spectrum is a well-known measure of the linear statistical relationship between two time series. In this paper, we extend this concept to several processes and define the generalized magnitude squared coherence (GMSC) spectrum as a function of the largest eigenvalue of a matrix containing all the pairwise complex coherence spectra. The GMSC is bounded between zero and one, and attains its maximum when all the processes are perfectly correlated at a given frequency. Furthermore, three different GMSC spectrum estimators, extending those previously proposed for the MSC of two processes, are presented. Specifically, we compare the Welch method, the minimum variance distortionless response (MVDR) estimator and a new estimator based on canonical correlation analysis (CCA). 208
The degree of impropriety (noncircularity) of complex random vectors(Peter J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 3909–3912,
April 2008.DOI:10.1109/ICASSP.2008.4518508. [BibTeX]
@inproceedings{Schreier:2008:The-degree-of-impropriety-noncircularit,
abstract = {A complex random vector is called improper (noncircular) if it is correlated with its complex conjugate. We consider measures for the degree of impropriety that are invariant under linear transformation. These measures are functions of the canonical correlations between the vector and its complex conjugate, which have been termed the circularity coefficients. However, we show that these circularity coefficients do not tell the whole story: Two random vectors with identical covariance matrix and identical circularity coefficients can still behave differently in second-order estimation and detection.},
author = {Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {The degree of impropriety (noncircularity) of complex random vectors},
year = {2008},
pages = {3909–3912},
doi = {10.1109/ICASSP.2008.4518508},
}
[Abstract]
A complex random vector is called improper (noncircular) if it is correlated with its complex conjugate. We consider measures for the degree of impropriety that are invariant under linear transformation. These measures are functions of the canonical correlations between the vector and its complex conjugate, which have been termed the circularity coefficients. However, we show that these circularity coefficients do not tell the whole story: Two random vectors with identical covariance matrix and identical circularity coefficients can still behave differently in second-order estimation and detection. 209
Near-capacity turbo equalization using optimized turbo codes(
Vladimir D. Trajkovic,
Minyue Fu and Peter J. Schreier)
Proc. Australasian Telecomm. Netw. Applic. Conf.,
pp. 480–484,
December 2007.DOI:10.1109/ATNAC.2007.4665276. [BibTeX]
@inproceedings{TrajkovicFuSchreier:2007:Near-capacity-turbo-equalization-using-o,
abstract = {In this paper we analyze a turbo equalization scheme that combines maximum a posteriori probability (MAP) equalization and turbo decoding. Our aim is to optimize the turbo equalizer in order to approach the information capacity limit for channels with severe inter-symbol interference (ISI). For this purpose, we perform an extensive search for turbo codes that give an SNR-BER performance closest to the channel information capacity limit. Our results show that the optimized turbo equalizer can approach the information capacity limit to within 0.7 dB. We also optimize the turbo equalizer in terms of the minimum number of required turbo decoding iterations. Our results show that a turbo decoder within a turbo equalization loop requires only a small number of iterations. Finally, our analysis reveals that when there are turbo codes with similar extrinsic information transfer characteristics, the computational complexity can be reduced by choosing the code with the smallest constraint length with no loss in SNR-BER performance.},
author = {Trajkovic, Vladimir D. and Fu, Minyue and Schreier, Peter J.},
booktitle = {{P}roc.\ {A}ustralasian {T}elecomm. {N}etw.\ {A}pplic.\ {C}onf.},
month = {{D}ecember},
title = {Near-capacity turbo equalization using optimized turbo codes},
year = {2007},
pages = {480–484},
doi = {10.1109/ATNAC.2007.4665276},
}
[Abstract]
In this paper we analyze a turbo equalization scheme that combines maximum a posteriori probability (MAP) equalization and turbo decoding. Our aim is to optimize the turbo equalizer in order to approach the information capacity limit for channels with severe inter-symbol interference (ISI). For this purpose, we perform an extensive search for turbo codes that give an SNR-BER performance closest to the channel information capacity limit. Our results show that the optimized turbo equalizer can approach the information capacity limit to within 0.7 dB. We also optimize the turbo equalizer in terms of the minimum number of required turbo decoding iterations. Our results show that a turbo decoder within a turbo equalization loop requires only a small number of iterations. Finally, our analysis reveals that when there are turbo codes with similar extrinsic information transfer characteristics, the computational complexity can be reduced by choosing the code with the smallest constraint length with no loss in SNR-BER performance. 210
Correlation coefficients for complex random vectors(Peter J. Schreier)
Proc. 41st Asilomar Conf. Signals Syst. Computers,
pp. 577–581,
November 2007.DOI:10.1109/ACSSC.2007.4487279. [BibTeX]
@inproceedings{Schreier:2007:Correlation-Coefficients-for-Complex-Ran,
abstract = {We consider the assessment of multivariate association between two complex random vectors. For complex data, there are three types of correlation coefficients, which account for rotational, reflectional, and total (i.e., rotational and reflectional) dependencies. We define and analyze these three types for different correlation coefficients, based on two popular correlation analysis techniques: canonical correlation analysis and multivariate linear regression (also known as half-canonical correlation analysis).},
author = {Schreier, Peter J.},
booktitle = {{P}roc.\ 41st\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Correlation coefficients for complex random vectors},
year = {2007},
pages = {577–581},
doi = {10.1109/ACSSC.2007.4487279},
}
[Abstract]
We consider the assessment of multivariate association between two complex random vectors. For complex data, there are three types of correlation coefficients, which account for rotational, reflectional, and total (i.e., rotational and reflectional) dependencies. We define and analyze these three types for different correlation coefficients, based on two popular correlation analysis techniques: canonical correlation analysis and multivariate linear regression (also known as half-canonical correlation analysis). 211
Frequency-domain properties of locally stationary improper second-order stochastic processes(
Patrik Wahlberg and Peter J. Schreier)
Proc. 41st Asilomar Conf. Signals Syst. Computers,
pp. 1093–1097,
November 2007.DOI:10.1109/ACSSC.2007.4487391. [BibTeX]
@inproceedings{WahlbergSchreier:2007:Frequency-domain-properties-of-locally-s,
abstract = {This paper concerns continuous-time second-order complex improper stochastic processes that satisfy Silverman's condition of local stationarity, which is a generalization of wide-sense stationarity (WSS). We study their spectral relations, proving a necessary condition that is related to a characterizing inequality of the pair of complementary spectral measure and spectral measure in the WSS case.},
author = {Wahlberg, Patrik and Schreier, Peter J.},
booktitle = {{P}roc.\ 41st\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Frequency-domain properties of locally stationary improper second-order stochastic processes},
year = {2007},
pages = {1093–1097},
doi = {10.1109/ACSSC.2007.4487391},
}
[Abstract]
This paper concerns continuous-time second-order complex improper stochastic processes that satisfy Silverman's condition of local stationarity, which is a generalization of wide-sense stationarity (WSS). We study their spectral relations, proving a necessary condition that is related to a characterizing inequality of the pair of complementary spectral measure and spectral measure in the WSS case. 212
Turbo equalization with irregular turbo codes(
Vladimir D. Trajkovic,
Minyue Fu and Peter J. Schreier)
Proc. 4th Int. Symp. Wireless Comm. Syst.,
pp. 153–157,
October 2007.DOI:10.1109/ISWCS.2007.4392320. [BibTeX]
@inproceedings{TrajkovicFuSchreier:2007:Turbo-Equalization-With-Irregular-Turbo-,
abstract = {We analyze a turbo equalization system that combines maximum a posteriori probability (MAP) equalization with irregular turbo codes. Our goal is to approach the information capacity limit for severe inter-symbol interference (ISI) channels. To this end, we optimize the degree profile of irregular turbo codes by maximizing the minimum distance between the mutual information transfer functions for the MAP equalizer and decoder. We show that turbo equalizers employing such optimized irregular turbo codes can approach the information capacity limit of some severe ISI channels within 0.75 dB.},
author = {Trajkovic, Vladimir D. and Fu, Minyue and Schreier, Peter J.},
booktitle = {{P}roc.\ 4th\ {I}nt.\ {S}ymp.\ {W}ireless {C}omm.\ {S}yst.},
month = {{O}ctober},
title = {Turbo equalization with irregular turbo codes},
year = {2007},
pages = {153–157},
doi = {10.1109/ISWCS.2007.4392320},
}
[Abstract]
We analyze a turbo equalization system that combines maximum a posteriori probability (MAP) equalization with irregular turbo codes. Our goal is to approach the information capacity limit for severe inter-symbol interference (ISI) channels. To this end, we optimize the degree profile of irregular turbo codes by maximizing the minimum distance between the mutual information transfer functions for the MAP equalizer and decoder. We show that turbo equalizers employing such optimized irregular turbo codes can approach the information capacity limit of some severe ISI channels within 0.75 dB. 213
Performance of STBC transmissions with real data(
J. A. García-Naya,
T. M. Fernández-Caramés,
H. J. Pérez-Iglesias,
M. González-López,
L. Castedo,
D. Ramírez,
I. Santamaría,
J. Pérez,
J. Vía and J. M. Torres-Royo)
Proc. IST Mobile & Wireless Comms. Summit,
Budapest, Hungary,
July 2007.DOI:10.1109/ISTMWC.2007.4299296. [BibTeX]
@inproceedings{Garcia-NayaFernandez-CaramesPerez-Iglesias:2007:Performance-of-STBC-transmissions-with,
abstract = {This paper presents a comparative study of three Space-Time Block Coding (STBC) techniques in realistic indoor scenarios. In particular, we focus on the Alamouti orthogonal scheme considering two types of Channel State Information (CSI) estimation: a conventional pilot-aided technique and a new blind method based on Second Order Statistics (SOS). We also considered a Differential (non-coherent) Space-Time Block code (DSTBC) that can be optimally decoded without CSI estimation, although it incurs in a 3 dB loss in performance. Experimental evaluation is carried out with a flexible and easy-to-use $2 \times 2$ MIMO platform at 2.4 GHz. Results show the excellent performance of the blind channel estimation technique in either Line-Of-Sight (LOS) and Non-LOS (NLOS) indoor scenarios.},
address = {Budapest, Hungary},
author = {J. A. Garc{\'i}a-Naya and T. M. Fern{\'a}ndez-Caram{\'e}s and H. J. P{\'e}rez-Iglesias and M. Gonz{\'a}lez-L{\'o}pez and L. Castedo and D. Ram{\'i}rez and I. Santamar{\'i}a and J. P{\'e}rez and J. V{\'i}a and J. M. Torres-Royo},
booktitle = {Proc.\ IST Mobile $\&$ Wireless Comms.\ Summit},
month = {{J}uly},
title = {Performance of {STBC} transmissions with real data},
year = {2007},
doi = {10.1109/ISTMWC.2007.4299296},
}
[Abstract]
This paper presents a comparative study of three Space-Time Block Coding (STBC) techniques in realistic indoor scenarios. In particular, we focus on the Alamouti orthogonal scheme considering two types of Channel State Information (CSI) estimation: a conventional pilot-aided technique and a new blind method based on Second Order Statistics (SOS). We also considered a Differential (non-coherent) Space-Time Block code (DSTBC) that can be optimally decoded without CSI estimation, although it incurs in a 3 dB loss in performance. Experimental evaluation is carried out with a flexible and easy-to-use 2 times 2 MIMO platform at 2.4 GHz. Results show the excellent performance of the blind channel estimation technique in either Line-Of-Sight (LOS) and Non-LOS (NLOS) indoor scenarios. 214
Spectra of multidimensional complex improper (almost) cyclostationary processes(
Patrik Wahlberg and Peter J. Schreier)
Proc. IEEE Int. Symp. Inform. Theory,
pp. 971–975,
June 2007.DOI:10.1109/ISIT.2007.4557350. [BibTeX]
@inproceedings{WahlbergSchreier:2007:Spectra-of-multidimensional-complex-impr,
abstract = {We analyze the spectral measure and complementary spectral measure for strongly harmonizable cyclostationary and almost cyclostationary multidimensional complex improper processes. We show that the off-diagonal components of the spectral measure are absolutely continuous with respect to the diagonal component, which is a generalization of a result for scalar processes. For scalar almost cyclostationary processes, we derive representation formulas for the complementary spectral measure and the off-diagonal components of the spectral measure, in terms of the diagonal component of the spectral measure. These results are similar to the cyclostationary case, with some modifications concerning the off-diagonal components of the complementary spectral measure.},
author = {Wahlberg, Patrik and Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {S}ymp.\ {I}nform.\ {T}heory},
month = {{J}une},
title = {Spectra of multidimensional complex improper (almost) cyclostationary processes},
year = {2007},
pages = {971–975},
doi = {10.1109/ISIT.2007.4557350},
}
[Abstract]
We analyze the spectral measure and complementary spectral measure for strongly harmonizable cyclostationary and almost cyclostationary multidimensional complex improper processes. We show that the off-diagonal components of the spectral measure are absolutely continuous with respect to the diagonal component, which is a generalization of a result for scalar processes. For scalar almost cyclostationary processes, we derive representation formulas for the complementary spectral measure and the off-diagonal components of the spectral measure, in terms of the diagonal component of the spectral measure. These results are similar to the cyclostationary case, with some modifications concerning the off-diagonal components of the complementary spectral measure. 215
A new interpretation of bilinear time-frequency distributions(Peter J. Schreier)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 1133–1136,
April 2007.DOI:10.1109/ICASSP.2007.366884. [BibTeX]
@inproceedings{Schreier:2007:A-New-Interpretation-of-Bilinear-Time-Fr,
abstract = {Wigner's theorem states that there exists no bilinear time-frequency distribution (TFD) that has correct marginals and is nonnegative everywhere. This means that any attempt to interpret a bilinear TFD as an energy or power distribution must be fraught with problems. In this paper, an alternative perspective is proposed, which allows a local interpretation at a point in the time-frequency plane. This approach is based on analyzing the properties of a chirping ellipse that, at a given time instant, gives the best local approximation of the signal from a given frequency. This chirping ellipse is described in terms of its mean shape, orientation, and direction of polarization (counterclockwise or clockwise). A time-frequency coherence measures the quality of the approximation that this ellipse presents. The ellipse parameters and the time-frequency coherence can be expressed in terms of the Rihaczek TFD},
author = {Schreier, Peter J.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {A new interpretation of bilinear time-frequency distributions},
year = {2007},
pages = {1133–1136},
doi = {10.1109/ICASSP.2007.366884},
}
[Abstract]
Wigner's theorem states that there exists no bilinear time-frequency distribution (TFD) that has correct marginals and is nonnegative everywhere. This means that any attempt to interpret a bilinear TFD as an energy or power distribution must be fraught with problems. In this paper, an alternative perspective is proposed, which allows a local interpretation at a point in the time-frequency plane. This approach is based on analyzing the properties of a chirping ellipse that, at a given time instant, gives the best local approximation of the signal from a given frequency. This chirping ellipse is described in terms of its mean shape, orientation, and direction of polarization (counterclockwise or clockwise). A time-frequency coherence measures the quality of the approximation that this ellipse presents. The ellipse parameters and the time-frequency coherence can be expressed in terms of the Rihaczek TFD 216
Causal cyclic Wiener filtering(
Mark S. Spurbeck,
Peter J. Schreier and Louis L. Scharf)
Proc. 40th Asilomar Conf. Signals Syst. Computers,
pp. 1425–1429,
November 2006.DOI:10.1109/ACSSC.2006.354993. [BibTeX]
@inproceedings{SchreierSpurbeckScharf:2006:Causal-cyclic-Wiener-filtering,
abstract = {We develop a causal filter bank implementation of the cyclic Wiener filter for periodically correlated (PC, or cyclostationary) time series. By converting the PC time series into a vector-valued wide-sense stationary (WSS) time series, we may utilize the existing literature on factorization of spectral density matrices. However, because PC analytic and equivalent baseband signals are generally improper, spectral factorization algorithms must be modified for the improper case. Then, given the spectral density matrix for the equivalent WSS vector process, a causal cyclic Wiener filter can be implemented as a multirate filter bank or an equivalent polyphase structure.},
author = {Spurbeck, Mark S. and Schreier, Peter J. and Scharf, Louis L.},
booktitle = {{P}roc.\ 40th\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Causal cyclic {Wiener} filtering},
year = {2006},
pages = {1425–1429},
doi = {10.1109/ACSSC.2006.354993},
}
[Abstract]
We develop a causal filter bank implementation of the cyclic Wiener filter for periodically correlated (PC, or cyclostationary) time series. By converting the PC time series into a vector-valued wide-sense stationary (WSS) time series, we may utilize the existing literature on factorization of spectral density matrices. However, because PC analytic and equivalent baseband signals are generally improper, spectral factorization algorithms must be modified for the improper case. Then, given the spectral density matrix for the equivalent WSS vector process, a causal cyclic Wiener filter can be implemented as a multirate filter bank or an equivalent polyphase structure. 217
A flexible testbed for the rapid prototyping of MIMO baseband modules(
D. Ramírez,
I. Santamaría,
J. Pérez,
J. Vía,
A. Tazón,
J. A. Garcia-Naya,
T. M. Fernandez-Carames,
M. Gonzalez Lopez,
H. J. Pérez Iglesias and L. Castedo)
Proc. Int. Symp. on Wireless Comm. Systems,
Valencia, Spain,
September 2006.DOI:10.1109/ISWCS.2006.4362407. [BibTeX]
@inproceedings{RamirezSantamariaPerez:2006:A-flexible-testbed-for-the-rapid-prototyping,
abstract = {Hardware platforms and testbeds are an essential tool to evaluate, in realistic scenarios, the performance of Multiple-Input-Multiple-Ouput (MIMO) systems. In this work we present a simple and easily reconfigurable $2 \times 2$ MIMO testbed for the rapid prototyping of the signal processing baseband functions. The signal generation module consists of a host PC equipped with a board that contains two high performance 100 MHz DACs and a 1 GB memory module that allows the transmission of extremely large frames of data. At the receiver side, we use another host PC equipped with two 105 MHz ADCs, another 1 GB memory module and a trigger that starts the acquisition process when the presence of signal is detected. The platform has been designed to operate at the ISM band of 2.4 GHz with a RF bandwidth of 20 MHz. In order to minimize the number of DAC and ADC circuits, signals are generated and acquired at an IF of 15 MHz. Upconversion to RF is performed with two RF vectorial signal generators (Agilent E4438C) and downconversion with two specific circuits designed from commercial components. Transmitter and receiver signal processing functions are implemented off-line in Matlab. To illustrate the performance and capabilities of the platform, we present the results of two experiments of a $2 \times 2$ MIMO transmission with Alamouti coding.},
address = {Valencia, Spain},
author = {D. Ram{\'i}rez and I. Santamar{\'i}a and J. P{\'e}rez and J. V{\'i}a and A. Taz{\'o}n and J. A. Garcia-Naya and T. M. Fernandez-Carames and M. Gonzalez Lopez and H. J. P{\'e}rez Iglesias and L. Castedo},
booktitle = {Proc.\ Int. Symp. on Wireless Comm. Systems},
month = {{S}eptember},
title = {A flexible testbed for the rapid prototyping of {MIMO} baseband modules},
year = {2006},
doi = {10.1109/ISWCS.2006.4362407},
}
[Abstract]
Hardware platforms and testbeds are an essential tool to evaluate, in realistic scenarios, the performance of Multiple-Input-Multiple-Ouput (MIMO) systems. In this work we present a simple and easily reconfigurable 2 times 2 MIMO testbed for the rapid prototyping of the signal processing baseband functions. The signal generation module consists of a host PC equipped with a board that contains two high performance 100 MHz DACs and a 1 GB memory module that allows the transmission of extremely large frames of data. At the receiver side, we use another host PC equipped with two 105 MHz ADCs, another 1 GB memory module and a trigger that starts the acquisition process when the presence of signal is detected. The platform has been designed to operate at the ISM band of 2.4 GHz with a RF bandwidth of 20 MHz. In order to minimize the number of DAC and ADC circuits, signals are generated and acquired at an IF of 15 MHz. Upconversion to RF is performed with two RF vectorial signal generators (Agilent E4438C) and downconversion with two specific circuits designed from commercial components. Transmitter and receiver signal processing functions are implemented off-line in Matlab. To illustrate the performance and capabilities of the platform, we present the results of two experiments of a 2 times 2 MIMO transmission with Alamouti coding. 218
Superposition coding with peak-power limitation(
Jun Tong,
Li Ping and Xiao Ma)
Proc. IEEE Int. Conf. Comm.,
pp. 1718–1723,
June 2006.DOI:10.1109/ICC.2006.254967. [BibTeX]
@inproceedings{TongPingMa:2006:Superposition-coding-with-peak-power-lim,
abstract = {This paper presents a peak-power-limited superposition coding scheme based on clipping. A low-complexity soft compensation algorithm (SCA) for combating the clipping effect is investigated. It can be easily combined with soft-input soft-output (SISO) decoding algorithms in an iterative manner. Various numerical results show that the SCA can effectively mitigate the performance loss due to clipping.},
author = {Tong, Jun and Ping, Li and Ma, Xiao},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {C}omm.},
month = {{J}une},
title = {Superposition coding with peak-power limitation},
year = {2006},
pages = {1718–1723},
doi = {10.1109/ICC.2006.254967},
}
[Abstract]
This paper presents a peak-power-limited superposition coding scheme based on clipping. A low-complexity soft compensation algorithm (SCA) for combating the clipping effect is investigated. It can be easily combined with soft-input soft-output (SISO) decoding algorithms in an iterative manner. Various numerical results show that the SCA can effectively mitigate the performance loss due to clipping. 219
Blind decoding of MISO-OSTBC systems based on principal component analysis(
J. Vía,
I. Santamaría,
J. Pérez and D. Ramírez)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
Toulouse, France,
May 2006.DOI:10.1109/ICASSP.2006.1661026. [BibTeX]
@inproceedings{ViaSantamariaPerez:2006:Blind-decoding-of-MISO-OSTBC-systems,
abstract = {In this paper, a new second-order statistics (SOS) based method for blind decoding of orthogonal space time block coded (OSTBC) systems with only one receive antenna is proposed. To avoid the in- herent ambiguities of this problem, the spatial correlation matrix of the source signals must be non-white and known at the receiver. In practice, this can be achieved by a number of simple linear preco- ding techniques at the transmitter side. More specifically, it is shown in the paper that if the source correlation matrix has different eigen- values, then the decoding process can be formulated as the problem of maximizing the sum of a set of weighted variances of the signal estimates. Exploiting the special structure of OSTBCs, this problem can be reduced to a principal component analysis (PCA) problem, which allows us to derive computationally efficient batch and adap- tive blind decoding algorithms. The algorithm works for any OSTBC (including the popular Alamouti code) with a single receive antenna. Some simulation results are presented to demonstrate the potential of the proposed procedure.},
address = {Toulouse, France},
author = {J. V{\'i}a and I. Santamar{\'i}a and J. P{\'e}rez and D. Ram{\'i}rez},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Blind decoding of {MISO-OSTBC} systems based on principal component analysis},
year = {2006},
doi = {10.1109/ICASSP.2006.1661026},
}
[Abstract]
In this paper, a new second-order statistics (SOS) based method for blind decoding of orthogonal space time block coded (OSTBC) systems with only one receive antenna is proposed. To avoid the in- herent ambiguities of this problem, the spatial correlation matrix of the source signals must be non-white and known at the receiver. In practice, this can be achieved by a number of simple linear preco- ding techniques at the transmitter side. More specifically, it is shown in the paper that if the source correlation matrix has different eigen- values, then the decoding process can be formulated as the problem of maximizing the sum of a set of weighted variances of the signal estimates. Exploiting the special structure of OSTBCs, this problem can be reduced to a principal component analysis (PCA) problem, which allows us to derive computationally efficient batch and adap- tive blind decoding algorithms. The algorithm works for any OSTBC (including the popular Alamouti code) with a single receive antenna. Some simulation results are presented to demonstrate the potential of the proposed procedure. 220
A statistical test for impropriety of complex random signals(
Peter J. Schreier,
Louis L. Scharf and Alfred Hanssen)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 796–799,
May 2006.DOI:10.1109/ICASSP.2006.1660774. [BibTeX]
@inproceedings{SchreierScharfHanssen:2006:A-Statistical-Test-for-Impropriety-of-Co,
abstract = {A complex random vector is called improper if it is correlated with its complex conjugate. In this paper, we present a generalized likelihood ratio test (GLRT) for impropriety. This test is compelling because it displays the right invariances: The proposed GLR is invariant to linear transformations on the data, including rotation and scaling, just as propriety is preserved by linear transformations. Because canonical correlations make up a complete, or maximal, set of invariants for the Hermitian and complementary covariance matrices under linear transformations, the GLR can be shown to be a function of the squared canonical correlations between the data and its complex conjugate. This validates our intuition that the internal coordinate system should not matter for this hypothesis test},
author = {Schreier, Peter J. and Scharf, Louis L. and Hanssen, Alfred},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {A statistical test for impropriety of complex random signals},
year = {2006},
pages = {796–799},
doi = {10.1109/ICASSP.2006.1660774},
}
[Abstract]
A complex random vector is called improper if it is correlated with its complex conjugate. In this paper, we present a generalized likelihood ratio test (GLRT) for impropriety. This test is compelling because it displays the right invariances: The proposed GLR is invariant to linear transformations on the data, including rotation and scaling, just as propriety is preserved by linear transformations. Because canonical correlations make up a complete, or maximal, set of invariants for the Hermitian and complementary covariance matrices under linear transformations, the GLR can be shown to be a function of the squared canonical correlations between the data and its complex conjugate. This validates our intuition that the internal coordinate system should not matter for this hypothesis test 221
Iterative decoding of superposition coding
(Jun Tong and Li Ping)
6th Int. Symp. Turbo Codes & Rel. Top., pp. 1–6, April 2006. [BibTeX]
@inproceedings{TongPing:2006:Iterative-decoding-of-superposition-codi,
abstract = {Clipping is applied to superposition coding systems to reduce the peak-to-average power ratio (PAPR) of the transmitted signal. The performance limit is investigated through evaluating the mutual information driven by the induced peak-power-limited input signals. It is shown that the channel capacity can be approached by clipped superposition coding systems. To alleviate the performance degradation due to clipping noises, we develop a soft compensation algorithm that is combined with soft-input-soft-output (SISO) decoding algorithms in an iterative manner. Simulation results show that with the proposed algorithm, most performance loss can be recovered.},
author = {Tong, Jun and Ping, Li},
booktitle = {6th\ {I}nt.\ {S}ymp.\ {T}urbo {C}odes \& {R}el.\ {T}op.},
month = {{A}pril},
title = {Iterative decoding of superposition coding},
year = {2006},
pages = {1–6},
}
[Abstract]
Clipping is applied to superposition coding systems to reduce the peak-to-average power ratio (PAPR) of the transmitted signal. The performance limit is investigated through evaluating the mutual information driven by the induced peak-power-limited input signals. It is shown that the channel capacity can be approached by clipped superposition coding systems. To alleviate the performance degradation due to clipping noises, we develop a soft compensation algorithm that is combined with soft-input-soft-output (SISO) decoding algorithms in an iterative manner. Simulation results show that with the proposed algorithm, most performance loss can be recovered.
222
A geometric interpretation of the Rihaczek time-frequency distribution for stochastic signals(
Peter J. Schreier,
Louis L. Scharf and Alfred Hanssen)
Proc. IEEE Int. Symp. Inform. Theory,
pp. 966–969,
September 2005.DOI:10.1109/ISIT.2005.1523481. [BibTeX]
@inproceedings{SchreierScharfHanssen:2005:A-geometric-interpretation-of-the-Rihacz,
abstract = {Based on the Cramer-Loeve spectral representation for a harmonizable random process, the Rihaczek distribution is a time- and frequency-shift covariant, bilinear time-frequency distribution. It can be expressed as a complex Hilbert space inner product between the time series and its infinitesimal stochastic Fourier generator. We show that we may attach an illuminating geometry to this inner product, wherein the cosine-squared of the angle between the time series and its infinitesimal stochastic Fourier generator is given by the Rihaczek distribution. We propose to construct estimators of the Rihaczek distribution using a factored kernel in Cohen's class of bilinear time-frequency distributions},
author = {Schreier, Peter J. and Scharf, Louis L. and Hanssen, Alfred},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {S}ymp.\ {I}nform.\ {T}heory},
month = {{S}eptember},
title = {A geometric interpretation of the {Rihaczek} time-frequency distribution for stochastic signals},
year = {2005},
pages = {966–969},
doi = {10.1109/ISIT.2005.1523481},
}
[Abstract]
Based on the Cramer-Loeve spectral representation for a harmonizable random process, the Rihaczek distribution is a time- and frequency-shift covariant, bilinear time-frequency distribution. It can be expressed as a complex Hilbert space inner product between the time series and its infinitesimal stochastic Fourier generator. We show that we may attach an illuminating geometry to this inner product, wherein the cosine-squared of the angle between the time series and its infinitesimal stochastic Fourier generator is given by the Rihaczek distribution. We propose to construct estimators of the Rihaczek distribution using a factored kernel in Cohen's class of bilinear time-frequency distributions 223
A note on aliasing in higher order spectra(Peter J. Schreier)
Proc. 6th Australian Comm. Theory Works.,
pp. 184–188,
February 2005.DOI:10.1109/AUSCTW.2005.1624249. [BibTeX]
@inproceedings{Schreier:2005:A-note-on-aliasing-in-higher-order-spect,
abstract = {There are two types of aliasing in higher order spectra: ``regular aliasing'' due to sampling below the Nyquist frequency, and ``higher order aliasing''. Spectra of discrete-time signals may suffer from higher-order aliasing if the signals are not sufficiently oversampled. By providing some insight into the cause of higher order aliasing, we show that higher order aliasing can just as well occur in second order spectra. More importantly, we demonstrate that spectra of stationary random signals defined as ensemble-averages and spectra of ergodic random signals defined as the Fourier transform of infinite time-averages never exhibit higher order aliasing},
author = {Schreier, Peter J.},
booktitle = {{P}roc.\ 6th\ {A}ustralian {C}omm.\ {T}heory {W}orks.},
month = {{F}ebruary},
title = {A note on aliasing in higher order spectra},
year = {2005},
pages = {184–188},
doi = {10.1109/AUSCTW.2005.1624249},
}
[Abstract]
There are two types of aliasing in higher order spectra: ``regular aliasing'' due to sampling below the Nyquist frequency, and ``higher order aliasing''. Spectra of discrete-time signals may suffer from higher-order aliasing if the signals are not sufficiently oversampled. By providing some insight into the cause of higher order aliasing, we show that higher order aliasing can just as well occur in second order spectra. More importantly, we demonstrate that spectra of stationary random signals defined as ensemble-averages and spectra of ergodic random signals defined as the Fourier transform of infinite time-averages never exhibit higher order aliasing 224
An adaptive channel tracking method for MIMO-OFDM systems(
Jun Tong,
Yaohuan Gong and Shengxian Sun)
Int. Conf. Comm. Circuits Syst.,
pp. 354–358,
June 2004.DOI:10.1109/ICCCAS.2004.1346098. [BibTeX]
@inproceedings{TongGongSun:2004:An-adaptive-channel-tracking-method-for-,
abstract = {The tracking of the time-varying channel is crucial for MIMO-OFDM wireless communication systems. Aiming at doubly-selective fading MIMO channels, we present a novel pilot pattern and the corresponding adaptive channel tracking algorithm. Compared with the traditional pilot patterns, the new pattern has higher frequency efficiency and is more suitable for large transmit arrays. The computational complexity, frequency efficiency and BER performance of the system assisted by the proposed channel tracking scheme are analyzed. Simulation results demonstrate that the proposed scheme can track the timevarying channel effectively.},
author = {Tong, Jun and Gong, Yaohuan and Sun, Shengxian},
booktitle = {{I}nt.\ {C}onf.\ {C}omm.\ {C}ircuits {S}yst.},
month = {{J}une},
title = {An adaptive channel tracking method for {MIMO-OFDM} systems},
year = {2004},
pages = {354–358},
doi = {10.1109/ICCCAS.2004.1346098},
}
[Abstract]
The tracking of the time-varying channel is crucial for MIMO-OFDM wireless communication systems. Aiming at doubly-selective fading MIMO channels, we present a novel pilot pattern and the corresponding adaptive channel tracking algorithm. Compared with the traditional pilot patterns, the new pattern has higher frequency efficiency and is more suitable for large transmit arrays. The computational complexity, frequency efficiency and BER performance of the system assisted by the proposed channel tracking scheme are analyzed. Simulation results demonstrate that the proposed scheme can track the timevarying channel effectively. 225
Polyspectra of analytic signals(
Peter J. Schreier and Louis L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 473–476,
May 2004.DOI:10.1109/ICASSP.2004.1326297. [BibTeX]
@inproceedings{SchreierScharf:2004:Polyspectra-of-analytic-signals,
abstract = {For complex signals, n-th order moment functions can be defined in 2n different ways, depending on the placement of complex conjugates. We demonstrate that, for stationary analytic signals, only a few of these different moments are actually required for a complete n-th order description. Which, and how many of them, depends on the signal's spectrum. We investigate properties of n-th order moments and spectra with different conjugation patterns and show how they provide different information about the signal.},
author = {Schreier, Peter J. and Scharf, Louis L.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Polyspectra of analytic signals},
year = {2004},
pages = {473–476},
doi = {10.1109/ICASSP.2004.1326297},
}
[Abstract]
For complex signals, n-th order moment functions can be defined in 2n different ways, depending on the placement of complex conjugates. We demonstrate that, for stationary analytic signals, only a few of these different moments are actually required for a complete n-th order description. Which, and how many of them, depends on the signal's spectrum. We investigate properties of n-th order moments and spectra with different conjugation patterns and show how they provide different information about the signal. 226
Widely-linear beamforming(
Todd McWhorter and Peter J. Schreier)
Proc. 37th Asilomar Conf. Signals Syst. Computers,
pp. 753–759,
November 2003.DOI:10.1109/ACSSC.2003.1292015. [BibTeX]
@inproceedings{McWhorterSchreier:2003:Widely-linear-beamforming,
abstract = {In this paper we describe a beamforming algorithm based on widely-linear rather than linear data models. Initially, we develop this beamformer by generalizing the Capon (MVDR) optimization problem. That is, if the objective is to minimize output power while maintaining a specified directional gain, then we show that the output power of the widely-linear beamformer is less than or equal to the output power of the Capon (MVDR) beamformer. This result is valid regardless of the ``true'' distribution of the data. We also derive the widely-linear beamformer by considering beamforming to be an estimation problem. Linear models assume that the composite covariance matrix formed from the real and imaginary parts of the array-snapshot has a particular structure. This structure is often summarized by stating that the covariance formed from the array snapshot and its transpose (not Hermitian transpose) is zero. We could also call these data ``proper'' Gaussian vectors. The beamformers in this paper are appropriate for situations in which these implicit assumptions are violated.},
author = {McWhorter, Todd and Schreier, Peter J.},
booktitle = {{P}roc.\ 37th\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Widely-linear beamforming},
year = {2003},
pages = {753–759},
doi = {10.1109/ACSSC.2003.1292015},
}
[Abstract]
In this paper we describe a beamforming algorithm based on widely-linear rather than linear data models. Initially, we develop this beamformer by generalizing the Capon (MVDR) optimization problem. That is, if the objective is to minimize output power while maintaining a specified directional gain, then we show that the output power of the widely-linear beamformer is less than or equal to the output power of the Capon (MVDR) beamformer. This result is valid regardless of the ``true'' distribution of the data. We also derive the widely-linear beamformer by considering beamforming to be an estimation problem. Linear models assume that the composite covariance matrix formed from the real and imaginary parts of the array-snapshot has a particular structure. This structure is often summarized by stating that the covariance formed from the array snapshot and its transpose (not Hermitian transpose) is zero. We could also call these data ``proper'' Gaussian vectors. The beamformers in this paper are appropriate for situations in which these implicit assumptions are violated. 227
Canonical coordinates are the right coordinate system for transform coding of noisy sources(
Peter J. Schreier,
Louis L. Scharf,
Tianjian Hu and Stephen D. Voran)
Proc. IEEE Works. Statistical Signal Proces.,
pp. 234–237,
September 2003.DOI:10.1109/SSP.2003.1289387. [BibTeX]
@inproceedings{SchreierScharfHu:2003:Canonical-coordinates-are-the-right-coor,
abstract = {Historically, transform coding of noisy sources has been performed by first estimating the message and then quantizing this estimate. We show that it is also optimum to first transform the noisy observations into canonical coordinates, quantize, apply a Wiener filter in this coordinate system, and then transform the result back to the original coordinates. Canonical coordinates are uncorrelated, and quantizing and Wiener filtering are applied to each component independently. Optimality of this approach can be proved assuming additive white quantization noise. Half canonical coordinates minimize the mean-squared error by minimizing the trace of the error covariance matrix and full canonical coordinates maximize information rate by minimizing the determinant of the error covariance matrix.},
author = {Schreier, Peter J. and Scharf, Louis L. and Hu, Tianjian and Voran, Stephen D.},
booktitle = {{P}roc.\ {IEEE} {W}orks.\ {S}tatistical {S}ignal {P}roces.},
month = {{S}eptember},
title = {Canonical coordinates are the right coordinate system for transform coding of noisy sources},
year = {2003},
pages = {234–237},
doi = {10.1109/SSP.2003.1289387},
}
[Abstract]
Historically, transform coding of noisy sources has been performed by first estimating the message and then quantizing this estimate. We show that it is also optimum to first transform the noisy observations into canonical coordinates, quantize, apply a Wiener filter in this coordinate system, and then transform the result back to the original coordinates. Canonical coordinates are uncorrelated, and quantizing and Wiener filtering are applied to each component independently. Optimality of this approach can be proved assuming additive white quantization noise. Half canonical coordinates minimize the mean-squared error by minimizing the trace of the error covariance matrix and full canonical coordinates maximize information rate by minimizing the determinant of the error covariance matrix. 228
A unified approach to performance comparisons between linear and widely linear processing(
Peter J. Schreier,
Louis L. Scharf and Clifford T. Mullis)
Proc. IEEE Works. Statistical Signal Proces.,
pp. 114–117,
September 2003.DOI:10.1109/SSP.2003.1289353. [BibTeX]
@inproceedings{SchreierScharfMullis:2003:A-unified-approach-to-performance-compar,
abstract = {Recently, a number of papers have been published that show significant performance gains can be obtained by accounting for the fact that communication signals can be improper. In this paper, we derive a general result comparing the performance of conventional processing, which ignores the improper nature of signals, with processing that takes it into account. In particular, for an estimation and a detection problem, we find that the performance gain, as measured by mean-squared error and deflection, respectively, can be as large as a factor of 2, but no larger. In a communications example, we show how this finding generalizes the result that coherent processing enjoys a 3 dB gain over non-coherent processing.},
author = {Schreier, Peter J. and Scharf, Louis L. and Mullis, Clifford T.},
booktitle = {{P}roc.\ {IEEE} {W}orks.\ {S}tatistical {S}ignal {P}roces.},
month = {{S}eptember},
title = {A unified approach to performance comparisons between linear and widely linear processing},
year = {2003},
pages = {114–117},
doi = {10.1109/SSP.2003.1289353},
}
[Abstract]
Recently, a number of papers have been published that show significant performance gains can be obtained by accounting for the fact that communication signals can be improper. In this paper, we derive a general result comparing the performance of conventional processing, which ignores the improper nature of signals, with processing that takes it into account. In particular, for an estimation and a detection problem, we find that the performance gain, as measured by mean-squared error and deflection, respectively, can be as large as a factor of 2, but no larger. In a communications example, we show how this finding generalizes the result that coherent processing enjoys a 3 dB gain over non-coherent processing. 229
The Karhunen-Loève expansion of improper complex random signals with applications in detection(
Peter J. Schreier and Louis L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 717–720,
April 2003.DOI:10.1109/ICASSP.2003.1201782. [BibTeX]
@inproceedings{SchreierScharf:2003:The-Karhunen-Loeve-expansion-of-improper,
abstract = {Non-stationary complex random signals are in general improper (not circularly symmetric), which means that their complementary covariance is non-zero. Since the Karhunen-Loeve expansion in its known form is only valid for proper processes, we derive the improper version of this expansion. It produces two sets of eigenvalues and an improper internal description. We use the Karhunen-Loeve expansion to solve the problem of detecting non-stationary improper complex random signals in additive white Gaussian noise. Using the deflection criterion we compare the performance of conventional processing, which ignores complementary covariances, with processing that takes these into account. The performance gain can be as great as a factor of 2.},
author = {Schreier, Peter J. and Scharf, Louis L.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{A}pril},
title = {The {Karhunen-Lo{\`{e}}ve} expansion of improper complex random signals with applications in detection},
year = {2003},
pages = {717–720},
doi = {10.1109/ICASSP.2003.1201782},
}
[Abstract]
Non-stationary complex random signals are in general improper (not circularly symmetric), which means that their complementary covariance is non-zero. Since the Karhunen-Loeve expansion in its known form is only valid for proper processes, we derive the improper version of this expansion. It produces two sets of eigenvalues and an improper internal description. We use the Karhunen-Loeve expansion to solve the problem of detecting non-stationary improper complex random signals in additive white Gaussian noise. Using the deflection criterion we compare the performance of conventional processing, which ignores complementary covariances, with processing that takes these into account. The performance gain can be as great as a factor of 2. 230
Reducing interference in stochastic time-frequency analysis without losing information(
Peter J. Schreier and Louis L. Scharf)
Proc. 36th Asilomar Conf. Signals Syst. Computers,
pp. 1565–1570,
November 2002.DOI:10.1109/ACSSC.2002.1197041. [BibTeX]
@inproceedings{SchreierScharf:2002:Reducing-interference-in-stochastic-time,
abstract = {The analytic signal is commonly used in stochastic time-frequency analysis in Cohen's class to reduce interference terms. However, we show that the usual time-frequency representation (TFR) based on the analytic signal gives only an incomplete signal description. This is because the analytic signal constructed from a non-stationary real signal is in general improper, which means that it has non-zero complementary correlation. We show how to augment the standard TFR by a complementary TFR to obtain a complete second-order characterization of the signal while still reducing interference terms compared to the TFR of the real signal.},
author = {Schreier, Peter J. and Scharf, Louis L.},
booktitle = {{P}roc.\ 36th\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Reducing interference in stochastic time-frequency analysis without losing information},
year = {2002},
pages = {1565–1570},
doi = {10.1109/ACSSC.2002.1197041},
}
[Abstract]
The analytic signal is commonly used in stochastic time-frequency analysis in Cohen's class to reduce interference terms. However, we show that the usual time-frequency representation (TFR) based on the analytic signal gives only an incomplete signal description. This is because the analytic signal constructed from a non-stationary real signal is in general improper, which means that it has non-zero complementary correlation. We show how to augment the standard TFR by a complementary TFR to obtain a complete second-order characterization of the signal while still reducing interference terms compared to the TFR of the real signal. 231
Canonical coordinates for reduced-rank estimation of improper complex random vectors(
Peter J. Schreier and Louis L. Scharf)
Proc. IEEE Int. Conf. Acoustics, Speech and Signal Process.,
pp. 1153–1156,
May 2002.DOI:10.1109/ICASSP.2002.5744004. [BibTeX]
@inproceedings{SchreierScharf:2002:Canonical-coordinates-for-reduced-rank-e,
abstract = {We consider the problem of minimum mean squared error (MMSE) estimation of complex random vectors in the improper case. Accounting for the information present in the complementary covariance requires the use of widely linear transformations. Based on these, we present the eigenanalysis of improper complex random vectors. This paves the way for a study of two different rank-reduced implementations of the complex Wiener Filter that make use of canonical coordinates: one that is optimum with respect to maximizing mutual information and one that minimizes mean squared error.},
author = {Schreier, Peter J. and Scharf, Louis L.},
booktitle = {{P}roc.\ {IEEE} {I}nt.\ {C}onf.\ {A}coustics, {S}peech and {S}ignal {P}rocess.},
month = {{M}ay},
title = {Canonical coordinates for reduced-rank estimation of improper complex random vectors},
year = {2002},
pages = {1153–1156},
doi = {10.1109/ICASSP.2002.5744004},
}
[Abstract]
We consider the problem of minimum mean squared error (MMSE) estimation of complex random vectors in the improper case. Accounting for the information present in the complementary covariance requires the use of widely linear transformations. Based on these, we present the eigenanalysis of improper complex random vectors. This paves the way for a study of two different rank-reduced implementations of the complex Wiener Filter that make use of canonical coordinates: one that is optimum with respect to maximizing mutual information and one that minimizes mean squared error. 232
Low-rank approximation of improper complex random vectors(
Peter J. Schreier and Louis L. Scharf)
Proc. 35th Asilomar Conf. Signals Syst. Computers,
pp. 597–601,
November 2001.DOI:10.1109/ACSSC.2001.986993. [BibTeX]
@inproceedings{SchreierScharf:2001:Low-rank-approximation-of-improper-compl,
abstract = {In reduced-rank signal processing for radar, sonar, and digital communications, we seek the right tradeoff between model bias and model variance for reconstructing signals from noisy data. Here, we extend the classical theory by considering the low-rank approximation of complex random vectors, which may or may not be proper. We show that, in general, widely linear approximation is superior to strictly linear approximation, unless the vector to be approximated is proper, in which case the optimum procedure is strictly linear. We analyze the case where the approximated random vector becomes proper in its internal coordinate system. This class of random vector, which we call generalized proper, possesses qualities similar to proper random vectors.},
author = {Schreier, Peter J. and Scharf, Louis L.},
booktitle = {{P}roc.\ 35th\ {A}silomar {C}onf.\ {S}ignals {S}yst.\ {C}omputers},
month = {{N}ovember},
title = {Low-rank approximation of improper complex random vectors},
year = {2001},
pages = {597–601},
doi = {10.1109/ACSSC.2001.986993},
}
[Abstract]
In reduced-rank signal processing for radar, sonar, and digital communications, we seek the right tradeoff between model bias and model variance for reconstructing signals from noisy data. Here, we extend the classical theory by considering the low-rank approximation of complex random vectors, which may or may not be proper. We show that, in general, widely linear approximation is superior to strictly linear approximation, unless the vector to be approximated is proper, in which case the optimum procedure is strictly linear. We analyze the case where the approximated random vector becomes proper in its internal coordinate system. This class of random vector, which we call generalized proper, possesses qualities similar to proper random vectors. 233
MAP decoding of linear block codes based on a sectionalized trellis of the dual code(
Peter J. Schreier and Daniel J. Costello, Jr.)
Proc. Int. Zurich Seminar Broadband Comm.,
pp. 271–278,
February 2000.DOI:10.1109/IZSBC.2000.829262. [BibTeX]
@inproceedings{SchreierCostello:2000:MAP-decoding-of-linear-block-codes-based,
abstract = {Block codes for use in turbo coding schemes provide an alternative to punctured convolutional codes when high rate component codes are needed. Since block codes have large, time-varying trellis diagrams, full maximum a posteriori (MAP) soft-in soft-out decoders are very complex. It is shown how to modify the MAP algorithm to utilize a sectionalized trellis diagram of the dual code for decoding, which minimizes computational complexity for high rate component codes. This paper also gives simulation results for some high rate block turbo codes},
author = {Schreier, Peter J. and {Costello, Jr.}, Daniel J.},
booktitle = {{P}roc.\ {I}nt.\ {Z}urich {S}eminar {B}roadband {C}omm.},
month = {{F}ebruary},
title = {{MAP} decoding of linear block codes based on a sectionalized trellis of the dual code},
year = {2000},
pages = {271–278},
doi = {10.1109/IZSBC.2000.829262},
}
[Abstract]
Block codes for use in turbo coding schemes provide an alternative to punctured convolutional codes when high rate component codes are needed. Since block codes have large, time-varying trellis diagrams, full maximum a posteriori (MAP) soft-in soft-out decoders are very complex. It is shown how to modify the MAP algorithm to utilize a sectionalized trellis diagram of the dual code for decoding, which minimizes computational complexity for high rate component codes. This paper also gives simulation results for some high rate block turbo codes