Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074649
Oliver M. Jeromin, V. Calhoun, M. Pattichis
This study explores the ability to reconstruct functional magnetic resonance imaging (fMRI) brain slices from a limited number of K-space samples. We use compressed sensing methods to reconstruct brain imaging activity using different K-space sampling geometries. To determine the optimal sampling geometry, we compute the reconstruction error. Here, for each geometry, we also estimate the optimal weighting parameters for the total variation (TV) norm and L-2 norm penalty functions. Initial results show that the optimal sampling geometry varies significantly as a function of the required reduction in K-space sampling density (for 60% to 90% reduction). Furthermore, the reconstructed fMRI slices can be used to accurately detect regions of neural activity from a largely reduced number of K-space samples.
{"title":"Optimal sampling geometries for TV-norm reconstruction of fMRI data","authors":"Oliver M. Jeromin, V. Calhoun, M. Pattichis","doi":"10.1109/ACSSC.2008.5074649","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074649","url":null,"abstract":"This study explores the ability to reconstruct functional magnetic resonance imaging (fMRI) brain slices from a limited number of K-space samples. We use compressed sensing methods to reconstruct brain imaging activity using different K-space sampling geometries. To determine the optimal sampling geometry, we compute the reconstruction error. Here, for each geometry, we also estimate the optimal weighting parameters for the total variation (TV) norm and L-2 norm penalty functions. Initial results show that the optimal sampling geometry varies significantly as a function of the required reduction in K-space sampling density (for 60% to 90% reduction). Furthermore, the reconstructed fMRI slices can be used to accurately detect regions of neural activity from a largely reduced number of K-space samples.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"122 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131936304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074640
S. Maranò, V. Matta, P. Willett
An energy-constrained wireless sensor network (WSN) is engaged in a binary detection task. An eavesdropper intercepts the messages sent by the nodes towards the central unit, thus trying to infer the state of the nature scrutinized by the system. We show that, under appropriate countermeasures against the eavesdropper, and adopting appropriate energy saving strategies, the system performances are characterized by a divergence-cost function D(beta) belonging to the class of the Ali-Silvey distances, where beta is related to the total energy consumption of the network. We also show that the most economic way of conveying information for detection is characterized by the related divergence per unit cost function D = supbeta D(beta)/beta. The properties of these performance metrics are investigated and two scenarios of interest are addressed: parallel and multiple access channels.
{"title":"On the divergence-cost function in distributed detection with a secrecy constraint","authors":"S. Maranò, V. Matta, P. Willett","doi":"10.1109/ACSSC.2008.5074640","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074640","url":null,"abstract":"An energy-constrained wireless sensor network (WSN) is engaged in a binary detection task. An eavesdropper intercepts the messages sent by the nodes towards the central unit, thus trying to infer the state of the nature scrutinized by the system. We show that, under appropriate countermeasures against the eavesdropper, and adopting appropriate energy saving strategies, the system performances are characterized by a divergence-cost function D(beta) belonging to the class of the Ali-Silvey distances, where beta is related to the total energy consumption of the network. We also show that the most economic way of conveying information for detection is characterized by the related divergence per unit cost function D = supbeta D(beta)/beta. The properties of these performance metrics are investigated and two scenarios of interest are addressed: parallel and multiple access channels.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"45 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132220201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074764
M. Ellis, W. Walker
Recently, we have developed a model-based adaptive beamforming algorithm, entitled dTONE, which significantly increases both image contrast and resolution by conducting a global optimization based on a model of a sparse set of hypothetical source locations. Due to the global nature of this optimization, a single bright source from an un-modeled location can cause significant degradation of the resulting image. As a result, the entire space from which signal may be received must be finely sampled, requiring a model of very large scale and computational complexity. We have developed a method that uses a reduced rank formulation of a subset of the hypothetical source locations to reduce the computational complexity of dTONE by several orders of magnitude with minimal degradation in image quality. Computation times were reduced by anywhere from 3.7 to 18.3 times while maintaining an image contrast and resolution far superior to that of conventional beamforming.
{"title":"Reduced rank formulation for increased computational efficiency in medical ultrasound model-based beamforming","authors":"M. Ellis, W. Walker","doi":"10.1109/ACSSC.2008.5074764","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074764","url":null,"abstract":"Recently, we have developed a model-based adaptive beamforming algorithm, entitled dTONE, which significantly increases both image contrast and resolution by conducting a global optimization based on a model of a sparse set of hypothetical source locations. Due to the global nature of this optimization, a single bright source from an un-modeled location can cause significant degradation of the resulting image. As a result, the entire space from which signal may be received must be finely sampled, requiring a model of very large scale and computational complexity. We have developed a method that uses a reduced rank formulation of a subset of the hypothetical source locations to reduce the computational complexity of dTONE by several orders of magnitude with minimal degradation in image quality. Computation times were reduced by anywhere from 3.7 to 18.3 times while maintaining an image contrast and resolution far superior to that of conventional beamforming.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130065713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074430
Bryan A. Yocom, T. Yudichak, B. Cour
One goal of active-passive data fusion is to combine the complementary information provided by active and passive sonar sensors to better perform signal processing. Here, investigation is restricted to passive direction of arrival tracking of a single target of interest in the presence of high SNR interferers. Prior information, available in a Bayesian framework, is used to increase track accuracy and decrease computational demand. Comparisons are made to a conventional approach that uses no prior information.
{"title":"Passive beamforming enhancements in relation to active-passive data fusion","authors":"Bryan A. Yocom, T. Yudichak, B. Cour","doi":"10.1109/ACSSC.2008.5074430","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074430","url":null,"abstract":"One goal of active-passive data fusion is to combine the complementary information provided by active and passive sonar sensors to better perform signal processing. Here, investigation is restricted to passive direction of arrival tracking of a single target of interest in the presence of high SNR interferers. Prior information, available in a Bayesian framework, is used to increase track accuracy and decrease computational demand. Comparisons are made to a conventional approach that uses no prior information.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133945592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074718
J. Salmi, A. Richter, V. Koivunen
This paper contributes to the field of N-way (N ges 3) tensor decompositions, which are increasingly popular in various signal processing applications. A novel PARATREE decomposition structure is introduced, accompanied with sequential unfolding SVD (SUSVD) algorithm. SUSVD applies a matrix SVD sequentially on the unfolded tensor, which is reshaped from the right hand basis vectors of the SVD of the previous mode. The consequent PARATREE model is related to the well known family of PARAFAC tensor decompositions, describing a tensor as a sum of rank-1 tensors. PARATREE is an efficient model to be used for orthogonal lower rank approximations, offering significant computational savings in algorithm implementations due to a hierarchical tree structure. The performance of the proposed algorithm is illustrated through an application of measurement noise suppression in wideband MIMO measurements.
{"title":"Sequential unfolding SVD for low rank orthogonal tensor approximation","authors":"J. Salmi, A. Richter, V. Koivunen","doi":"10.1109/ACSSC.2008.5074718","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074718","url":null,"abstract":"This paper contributes to the field of N-way (N ges 3) tensor decompositions, which are increasingly popular in various signal processing applications. A novel PARATREE decomposition structure is introduced, accompanied with sequential unfolding SVD (SUSVD) algorithm. SUSVD applies a matrix SVD sequentially on the unfolded tensor, which is reshaped from the right hand basis vectors of the SVD of the previous mode. The consequent PARATREE model is related to the well known family of PARAFAC tensor decompositions, describing a tensor as a sum of rank-1 tensors. PARATREE is an efficient model to be used for orthogonal lower rank approximations, offering significant computational savings in algorithm implementations due to a hierarchical tree structure. The performance of the proposed algorithm is illustrated through an application of measurement noise suppression in wideband MIMO measurements.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"347 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132608853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074610
R. Ives, R. Broussard, L. Kennell, R. Rakvic, D. Etter
The authors present a new algorithm for iris recognition. Segmentation is based on local statistics, and after segmentation, the image is subjected to contrast-limited, adaptive histogram equalization. Feature extraction is then conducted using two directional filters (vertically and horizontally oriented). The presence (or absence) of ridges and their dominant directions are determined, based on maximum directional filter response. Templates are compared using fractional Hamming distance as a metric for a match/non match determination. This ridge-energy-direction (RED) algorithm reduces the effects of illumination, since only direction is used. Results are presented that utilize four iris databases, and some comparison of recognition performance against a Daugman-based algorithm is provided.
{"title":"Iris recognition using the Ridge Energy Direction (RED) algorithm","authors":"R. Ives, R. Broussard, L. Kennell, R. Rakvic, D. Etter","doi":"10.1109/ACSSC.2008.5074610","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074610","url":null,"abstract":"The authors present a new algorithm for iris recognition. Segmentation is based on local statistics, and after segmentation, the image is subjected to contrast-limited, adaptive histogram equalization. Feature extraction is then conducted using two directional filters (vertically and horizontally oriented). The presence (or absence) of ridges and their dominant directions are determined, based on maximum directional filter response. Templates are compared using fractional Hamming distance as a metric for a match/non match determination. This ridge-energy-direction (RED) algorithm reduces the effects of illumination, since only direction is used. Results are presented that utilize four iris databases, and some comparison of recognition performance against a Daugman-based algorithm is provided.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"418 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132793591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074795
L. Thiele, M. Schellmann, T. Wirth, V. Jungnickel
Multi-cellular radio systems are often limited due to the presence of cochannel interference. Physical layer concepts as e.g. interference rejection combining, optimize the receiver side and thus strengthen the signal while combating the interference at the terminal side only. It is well known that joint transceiver optimization, i.e. coordinated joint transmission from several base stations, yields large capacity improvement for downlink transmission. However, the performance highly depends on the available channel knowledge. We focus on how to realize a decentralized and limited cooperative downlink transmission in a multi-cellular network. This yields the crucial question: Is an efficient cooperative transmission possible by using simple channel quality identifiers, or is channel state information at the transmitter mandatory? Further, we use minimum mean square error equalization at the terminal side to combat residual cochannel interference. For baseline we apply receiver optimization only and compare these results with those obtained from cooperative transmission. We demonstrate potential capacity gains in a cellular orthogonal frequency division multiplexing system and their scaling with the number of cooperating antenna arrays.
{"title":"Cooperative multi-user MIMO based on limited feedback in downlink OFDM systems","authors":"L. Thiele, M. Schellmann, T. Wirth, V. Jungnickel","doi":"10.1109/ACSSC.2008.5074795","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074795","url":null,"abstract":"Multi-cellular radio systems are often limited due to the presence of cochannel interference. Physical layer concepts as e.g. interference rejection combining, optimize the receiver side and thus strengthen the signal while combating the interference at the terminal side only. It is well known that joint transceiver optimization, i.e. coordinated joint transmission from several base stations, yields large capacity improvement for downlink transmission. However, the performance highly depends on the available channel knowledge. We focus on how to realize a decentralized and limited cooperative downlink transmission in a multi-cellular network. This yields the crucial question: Is an efficient cooperative transmission possible by using simple channel quality identifiers, or is channel state information at the transmitter mandatory? Further, we use minimum mean square error equalization at the terminal side to combat residual cochannel interference. For baseline we apply receiver optimization only and compare these results with those obtained from cooperative transmission. We demonstrate potential capacity gains in a cellular orthogonal frequency division multiplexing system and their scaling with the number of cooperating antenna arrays.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126587590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074541
S. Stańczak, Michal Kaliszan, N. Bambos
In [1], the authors proposed an admission control scheme for power-controlled wireless networks with linear interference functions (fixed receivers). This paper extends the main results of [1] to standard interference functions that include optimal reception in the sense of maximizing the signal-to-interference ratios as a special case. Moreover, we consider the possibility of transmitter side optimization.
{"title":"Admission control for power-controlled wireless networks under general interference functions","authors":"S. Stańczak, Michal Kaliszan, N. Bambos","doi":"10.1109/ACSSC.2008.5074541","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074541","url":null,"abstract":"In [1], the authors proposed an admission control scheme for power-controlled wireless networks with linear interference functions (fixed receivers). This paper extends the main results of [1] to standard interference functions that include optimal reception in the sense of maximizing the signal-to-interference ratios as a special case. Moreover, we consider the possibility of transmitter side optimization.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"254 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117315859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074417
P. Layec, P. Piantanida, R. Visoz, A. Berthet
Linear transceiver design for multiple access channels (MACs) with spatial correlation at both transmitter and receiver is investigated in the presence of inaccurate channel state information (CSI). We consider a training-based channel estimation at the receiver while a limited-rate feedback channel conveys the transmitter information. Imperfect knowledge comes from the channel estimation errors and the quantization noise. Restricting the decoder to be linear yields to minimize of the sum-mean square error (sum-MSE) subject to individual power constraints. Although no closed-form solution is possible in a multi-user setting, an efficient iterative algorithm relying on the KKT conditions is derived. Numerical results show sum-MSE and BER performance to measure the sensitivity of a mismatched design as well as the effect of quantization noise. Furthermore, the study of channel uncertainty enables to assess the relative impact of imperfect CSI at both ends.
{"title":"Transceiver design for sum-MSE optimization in MIMO-MAC with imperfect channel estimation","authors":"P. Layec, P. Piantanida, R. Visoz, A. Berthet","doi":"10.1109/ACSSC.2008.5074417","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074417","url":null,"abstract":"Linear transceiver design for multiple access channels (MACs) with spatial correlation at both transmitter and receiver is investigated in the presence of inaccurate channel state information (CSI). We consider a training-based channel estimation at the receiver while a limited-rate feedback channel conveys the transmitter information. Imperfect knowledge comes from the channel estimation errors and the quantization noise. Restricting the decoder to be linear yields to minimize of the sum-mean square error (sum-MSE) subject to individual power constraints. Although no closed-form solution is possible in a multi-user setting, an efficient iterative algorithm relying on the KKT conditions is derived. Numerical results show sum-MSE and BER performance to measure the sensitivity of a mismatched design as well as the effect of quantization noise. Furthermore, the study of channel uncertainty enables to assess the relative impact of imperfect CSI at both ends.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131098163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-10-01DOI: 10.1109/ACSSC.2008.5074741
J. Moore, M. Thornton, D. Matula
We introduce an implementation of a radix 4 dual recoding procedure for the squaring operation of an n-bit number which reduces the number of bit product terms employed in the previously known squaring methods obtained by either Booth radix-4 recoded multiplication or by radix 2 squaring. Several other squaring algorithms have been developed such as [WSM99], [YW01], and [SNC01]. Employing the dual recoded radix-4 procedure for design of a squaring circuit introduces a significant reduction in power and area. Architecturally, radix-4 dual recoded squaring uses only the 1's complement representation which allows for a simpler PPG structure as compared to the 2's complement representation required for Booth radix-4 multiplication.
{"title":"A low power radix-4 dual recoded integer squaring implementation for use in design of application specific arithmetic circuits","authors":"J. Moore, M. Thornton, D. Matula","doi":"10.1109/ACSSC.2008.5074741","DOIUrl":"https://doi.org/10.1109/ACSSC.2008.5074741","url":null,"abstract":"We introduce an implementation of a radix 4 dual recoding procedure for the squaring operation of an n-bit number which reduces the number of bit product terms employed in the previously known squaring methods obtained by either Booth radix-4 recoded multiplication or by radix 2 squaring. Several other squaring algorithms have been developed such as [WSM99], [YW01], and [SNC01]. Employing the dual recoded radix-4 procedure for design of a squaring circuit introduces a significant reduction in power and area. Architecturally, radix-4 dual recoded squaring uses only the 1's complement representation which allows for a simpler PPG structure as compared to the 2's complement representation required for Booth radix-4 multiplication.","PeriodicalId":416114,"journal":{"name":"2008 42nd Asilomar Conference on Signals, Systems and Computers","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132846859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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