Pub Date : 2006-07-02DOI: 10.1109/SPAWC.2006.346340
S. Rhioui, E. Moreau
This paper considers the problem of blind separation of a MIMO convolutive mixture of i.i.d. source signals. Separation criteria are considered for the overall extraction of source signals according to the use of so-called reference signals. We present a new MIMO contrast function using reference signals, which is moreover seen to have joint-diagonalization interpretation. A link with the PARAFAC decomposition is also emphasized. Finally the performance are investigated through computer simulations
{"title":"Convolutive Separation of I.I.D. Signals Based on Simultaneous Tensors Diagonalization","authors":"S. Rhioui, E. Moreau","doi":"10.1109/SPAWC.2006.346340","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346340","url":null,"abstract":"This paper considers the problem of blind separation of a MIMO convolutive mixture of i.i.d. source signals. Separation criteria are considered for the overall extraction of source signals according to the use of so-called reference signals. We present a new MIMO contrast function using reference signals, which is moreover seen to have joint-diagonalization interpretation. A link with the PARAFAC decomposition is also emphasized. Finally the performance are investigated through computer simulations","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133145418","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346371
S. M. Saberali
Overlaying spread spectrum systems on narrowband services has been proposed as a way to take greater bandwidth efficients with respect to sparsely narrowband systems. It is shown that, the performance of both narrowband and spread spectrum systems in a overlay situation significantly degraded by each other. This paper presents a new nonlinear detector which enhances the performance of narrowband considerably. In our approach we use maximum likelihood (ML) as maximum entropy, which are two optimal criteria. Computer simulation results show that the proposed detector has much better performance than the conventional matched filter. The estimated narrowband signal can be subtracted from received signal in the spread spectrum receiver to enhance its performance
{"title":"New Nonlinear Detector for Interference Cancellation in Spread Spectrum Overlay Systems","authors":"S. M. Saberali","doi":"10.1109/SPAWC.2006.346371","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346371","url":null,"abstract":"Overlaying spread spectrum systems on narrowband services has been proposed as a way to take greater bandwidth efficients with respect to sparsely narrowband systems. It is shown that, the performance of both narrowband and spread spectrum systems in a overlay situation significantly degraded by each other. This paper presents a new nonlinear detector which enhances the performance of narrowband considerably. In our approach we use maximum likelihood (ML) as maximum entropy, which are two optimal criteria. Computer simulation results show that the proposed detector has much better performance than the conventional matched filter. The estimated narrowband signal can be subtracted from received signal in the spread spectrum receiver to enhance its performance","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128659096","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346347
I. Perisa, J. Lindner
In previous works, many efficient phase-based estimators with small computational complexity have been proposed. Most of them suffer from a very high threshold - i.e. below a certain signal-to-noise ratio (SNR) the estimator variance increases rapidly. Most of the approaches that improve the threshold are quite complex or have a limited estimation range. In a previous paper it was shown that iterative frequency offset estimation schemes can achieve a low threshold at a moderate complexity. Here we show how they can be combined with different estimators to achieve a faster convergence rate. This enables the construction of estimators that can easily be adapted to different requirements concerning estimation range, performance, and complexity
{"title":"Iterative Phase-Based Frequency Estimation with Extended Threshold and Estimation Range at Moderate Complexity","authors":"I. Perisa, J. Lindner","doi":"10.1109/SPAWC.2006.346347","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346347","url":null,"abstract":"In previous works, many efficient phase-based estimators with small computational complexity have been proposed. Most of them suffer from a very high threshold - i.e. below a certain signal-to-noise ratio (SNR) the estimator variance increases rapidly. Most of the approaches that improve the threshold are quite complex or have a limited estimation range. In a previous paper it was shown that iterative frequency offset estimation schemes can achieve a low threshold at a moderate complexity. Here we show how they can be combined with different estimators to achieve a faster convergence rate. This enables the construction of estimators that can easily be adapted to different requirements concerning estimation range, performance, and complexity","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127217171","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346350
A. Sezgin, Eduard Axel Jorswieck, H. Boche
It was shown recently, that in case of Rayleigh fading and an uninformed transmitter the average rate achieved with quasi-orthogonal space-time block codes (QSTBC), which use an orthogonal space-time block code (OSTBC) as building element, is equal to the average rate of the underlying OSTBC. In this work, we assume that the transmitter knows the mean channel matrix in a more general scenario either by feedback or channel estimation and the receiver has perfect CSI. We then analyze the optimal transmit strategy with respect to the average rate. Interestingly, at first the optimization problem is non-convex. However, after choosing the optimal directions, the remaining power allocation problem turns out to be convex. We analyze the impact of the mean component on the average rate, the optimal transmit strategy including the optimal power allocation. We show that in case of mean knowledge the QSTBC outperform the OSTBC with respect to the average rate and illustrate our theoretical results using numerical simulations
{"title":"On the Average Rate of Precoded QSTBC in MIMO Channels with Non-Zero Mean","authors":"A. Sezgin, Eduard Axel Jorswieck, H. Boche","doi":"10.1109/SPAWC.2006.346350","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346350","url":null,"abstract":"It was shown recently, that in case of Rayleigh fading and an uninformed transmitter the average rate achieved with quasi-orthogonal space-time block codes (QSTBC), which use an orthogonal space-time block code (OSTBC) as building element, is equal to the average rate of the underlying OSTBC. In this work, we assume that the transmitter knows the mean channel matrix in a more general scenario either by feedback or channel estimation and the receiver has perfect CSI. We then analyze the optimal transmit strategy with respect to the average rate. Interestingly, at first the optimization problem is non-convex. However, after choosing the optimal directions, the remaining power allocation problem turns out to be convex. We analyze the impact of the mean component on the average rate, the optimal transmit strategy including the optimal power allocation. We show that in case of mean knowledge the QSTBC outperform the OSTBC with respect to the average rate and illustrate our theoretical results using numerical simulations","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"2011 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130812723","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346464
T. Ramstad
The paper presents performance limits for transmitting correlated Gaussian signals over additive, Gaussian channels with memory and limited transmit power. Both absolute performance limits as well as performance limits for linear systems are given. A bandwidth matching technique is introduced for the adaptation of the signal to the channel. This can be used as an instrument for resource allocation when combining subband source decomposition and OFDM transmission in a source-channel coding environment
{"title":"On Joint Source-Channel Coding for the Non-White Gaussian Case","authors":"T. Ramstad","doi":"10.1109/SPAWC.2006.346464","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346464","url":null,"abstract":"The paper presents performance limits for transmitting correlated Gaussian signals over additive, Gaussian channels with memory and limited transmit power. Both absolute performance limits as well as performance limits for linear systems are given. A bandwidth matching technique is introduced for the adaptation of the signal to the channel. This can be used as an instrument for resource allocation when combining subband source decomposition and OFDM transmission in a source-channel coding environment","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134479450","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346471
Andrew G. Klein, Pierre Duhamel
We consider blind channel estimation for orthogonal modulation and its variants - which include pulse position modulation (PPM) and frequency shift keying (FSK). While equalization of this modulation format has been given some attention by the research community, little attention has been paid to techniques for (blind) channel estimation in systems employing orthogonal modulation. We extend classical subspace-based blind techniques in a way that is suitable for use with orthogonal modulation. Unlike classical subspace-based blind channel estimators, however, our scheme does not require oversampling and/or multiple sensors. After introducing the system model, we present the proposed method of channel estimation, and include conditions under which the scheme is valid. We conclude with several simulations.
{"title":"Subspace-Based Blind Channel Identification for Orthogonal Modulation","authors":"Andrew G. Klein, Pierre Duhamel","doi":"10.1109/SPAWC.2006.346471","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346471","url":null,"abstract":"We consider blind channel estimation for orthogonal modulation and its variants - which include pulse position modulation (PPM) and frequency shift keying (FSK). While equalization of this modulation format has been given some attention by the research community, little attention has been paid to techniques for (blind) channel estimation in systems employing orthogonal modulation. We extend classical subspace-based blind techniques in a way that is suitable for use with orthogonal modulation. Unlike classical subspace-based blind channel estimators, however, our scheme does not require oversampling and/or multiple sensors. After introducing the system model, we present the proposed method of channel estimation, and include conditions under which the scheme is valid. We conclude with several simulations.","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129401952","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346382
P. Shariatpanahi, B. Khalaj
Adaptive scheduling schemes which consider channel conditions are examples of cross-layer design in wireless networks. Research work which has been done on optimizing the performance of scheduling systems have shown that in each time slot it is better to transmit to the users with the best channel condition. In order to realize such schemes, most of earlier works have considered perfect feedback channels to send channel state information (CSI) to the scheduler. However, in practical systems there are some sources of imperfectness in feedback channels such as delay and quantization error. In this paper, we consider the effect of CSI delay on the performance of such systems. A new delay-aware scheduling scheme is proposed, which takes into account the difference in delay profiles of different users in the scheduling algorithm. Also a reduced complexity alternative scheme is investigated
{"title":"Delay-Aware Scheduling in Heterogeneous Multiuser Systems","authors":"P. Shariatpanahi, B. Khalaj","doi":"10.1109/SPAWC.2006.346382","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346382","url":null,"abstract":"Adaptive scheduling schemes which consider channel conditions are examples of cross-layer design in wireless networks. Research work which has been done on optimizing the performance of scheduling systems have shown that in each time slot it is better to transmit to the users with the best channel condition. In order to realize such schemes, most of earlier works have considered perfect feedback channels to send channel state information (CSI) to the scheduler. However, in practical systems there are some sources of imperfectness in feedback channels such as delay and quantization error. In this paper, we consider the effect of CSI delay on the performance of such systems. A new delay-aware scheduling scheme is proposed, which takes into account the difference in delay profiles of different users in the scheduling algorithm. Also a reduced complexity alternative scheme is investigated","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131390065","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346388
L. G. Barbero, John S. Thompson
A new detection algorithm for uncoded multiple input-multiple output (MIMO) systems based on the complex version of the sphere decoder (SD) is presented in this paper. The algorithm performs a fixed number of operations to detect the symbols, independent of the noise level. The algorithm achieves this by combining a novel channel matrix preprocessing with a search through a small subset of the complete receive constellation. Simulation results show it has only a very small bit error ratio (BER) degradation compared to the original SD while being suited for a fully-pipelined hardware implementation due to its fixed complexity
{"title":"A Fixed-Complexity MIMO Detector Based on the Complex Sphere Decoder","authors":"L. G. Barbero, John S. Thompson","doi":"10.1109/SPAWC.2006.346388","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346388","url":null,"abstract":"A new detection algorithm for uncoded multiple input-multiple output (MIMO) systems based on the complex version of the sphere decoder (SD) is presented in this paper. The algorithm performs a fixed number of operations to detect the symbols, independent of the noise level. The algorithm achieves this by combining a novel channel matrix preprocessing with a search through a small subset of the complete receive constellation. Simulation results show it has only a very small bit error ratio (BER) degradation compared to the original SD while being suited for a fully-pipelined hardware implementation due to its fixed complexity","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115922485","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346425
G. Scutari, S. Barbarossa, L. Pescosolido
In this paper we focus on a sensor network scheme whose nodes are locally coupled oscillators that evolve in time according to a differential equation, whose parameters depend on the local estimate. The proposed system is capable, by self-synchronization, to reach the network consensus that coincides with the globally optimum maximum likelihood estimate, even though each sensor is only locally coupled with nearby nodes. Our main contribution is to study the effect of propagation delay on both the synchronization capability of the system and the final estimate. We provide delay-independent conditions for the proposed system to synchronize, and we derive closed-form expression of the synchronized state. Interestingly, the effect of propagation delays is simply to introduce a bias on the final estimate, that depends on the network topology and on the values of the delays. The analysis of this bias, suggest us how to design the coupling mechanism in order to alleviate it or even remove it
{"title":"Optimal Decentralized Estimation Through Self-Synchronizing Networks in the Presence of Propagation Delays","authors":"G. Scutari, S. Barbarossa, L. Pescosolido","doi":"10.1109/SPAWC.2006.346425","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346425","url":null,"abstract":"In this paper we focus on a sensor network scheme whose nodes are locally coupled oscillators that evolve in time according to a differential equation, whose parameters depend on the local estimate. The proposed system is capable, by self-synchronization, to reach the network consensus that coincides with the globally optimum maximum likelihood estimate, even though each sensor is only locally coupled with nearby nodes. Our main contribution is to study the effect of propagation delay on both the synchronization capability of the system and the final estimate. We provide delay-independent conditions for the proposed system to synchronize, and we derive closed-form expression of the synchronized state. Interestingly, the effect of propagation delays is simply to introduce a bias on the final estimate, that depends on the network topology and on the values of the delays. The analysis of this bias, suggest us how to design the coupling mechanism in order to alleviate it or even remove it","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"190 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115494685","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 : 2006-07-02DOI: 10.1109/SPAWC.2006.346396
James C. F. Li, S. Dey
In this paper we address a sensor network lifetime optimization problem, where the network is given a task of reconstructing a Gaussian source with a specified rate-distortion constraint. The multiple agents observing the source relay their information through a multihop network to a sink or a base station. Although this problem has been addressed by other authors recently, only upper and lower bounds were obtained to the optimal lifetime as the nonlinear optimization problem was approximated by linearized constraints. We show that by a clever variable substitution, the original nonlinear optimization problem can be reformulated as a convex optimization problem and can be solved by sophisticated convex optimization tools. We provide numerical results comparing our optimal lifetime with the upper and lower bounds obtained in previous work and demonstrate that those bounds are not very tight. Some possible future research directions are mentioned in the concluding remarks
{"title":"Lifetime Optimization for Multi-hop Wireless Sensor Networks with Rate Distortion Constraints","authors":"James C. F. Li, S. Dey","doi":"10.1109/SPAWC.2006.346396","DOIUrl":"https://doi.org/10.1109/SPAWC.2006.346396","url":null,"abstract":"In this paper we address a sensor network lifetime optimization problem, where the network is given a task of reconstructing a Gaussian source with a specified rate-distortion constraint. The multiple agents observing the source relay their information through a multihop network to a sink or a base station. Although this problem has been addressed by other authors recently, only upper and lower bounds were obtained to the optimal lifetime as the nonlinear optimization problem was approximated by linearized constraints. We show that by a clever variable substitution, the original nonlinear optimization problem can be reformulated as a convex optimization problem and can be solved by sophisticated convex optimization tools. We provide numerical results comparing our optimal lifetime with the upper and lower bounds obtained in previous work and demonstrate that those bounds are not very tight. Some possible future research directions are mentioned in the concluding remarks","PeriodicalId":414942,"journal":{"name":"2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115219238","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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