Pub Date : 2008-07-06DOI: 10.1109/SPAWC.2008.4641649
James C. F. Li, S. Dey
Motivated by delay-sensitive information transmission applications, we propose an expected achievable rate maximization scheme with a K-block delay constraint on data transmission using a three node cooperative relay network assuming a block fading channel model. Channel information is fed back to the transmitter only in a causal fashion, so that the optimal power allocation strategy is only based on the current and past channel gains.We consider the two simplest schemes for information transmission using a three node (a source, a relay and a destination) relay network, namely the amplify and forward (AF) and decode and forward (DF) protocols. We use a dynamic programming based methodology to solve the (K-block delay constrained) expected capacity maximization problem with a short term (over K blocks) sum power (total transmission power of the source and the relay) constraint. Furthermore, two simple power allocation schemes for high and low SNR situations are proposed. Extensive numerical results are presented for Rayleigh fading channels, including results demonstrating the accuracy of the high/low SNR approximation based power allocation schemes.
{"title":"Delay-constrained achievable rate maximization in wireless relay networks with causal feedback","authors":"James C. F. Li, S. Dey","doi":"10.1109/SPAWC.2008.4641649","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641649","url":null,"abstract":"Motivated by delay-sensitive information transmission applications, we propose an expected achievable rate maximization scheme with a K-block delay constraint on data transmission using a three node cooperative relay network assuming a block fading channel model. Channel information is fed back to the transmitter only in a causal fashion, so that the optimal power allocation strategy is only based on the current and past channel gains.We consider the two simplest schemes for information transmission using a three node (a source, a relay and a destination) relay network, namely the amplify and forward (AF) and decode and forward (DF) protocols. We use a dynamic programming based methodology to solve the (K-block delay constrained) expected capacity maximization problem with a short term (over K blocks) sum power (total transmission power of the source and the relay) constraint. Furthermore, two simple power allocation schemes for high and low SNR situations are proposed. Extensive numerical results are presented for Rayleigh fading channels, including results demonstrating the accuracy of the high/low SNR approximation based power allocation schemes.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123744382","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641577
J. Chong, Y. Sung, D. Sung
The performance of the carrier sense multiple access/collision avoidance (CSMA/CA) protocol under the presence of carrier sensing errors is analyzed. Two types of carrier sensing errors, false alarm and miss detection, are considered, and their impact on system performance is analyzed using a new CSMA/CA model based on a Markov chain capturing the sensing errors at the physical layer. The throughput as a function of these sensing error probabilities as well as other CSMA/CA parameters is obtained. It is shown that the throughput loss by a poorly chosen sensing threshold is tolerable at intermediate values of the ratio of the packet size to the contention window size, whereas care should be taken in choosing the sensing threshold when the ratio is small or large.
{"title":"Cross-layer performance analysis for CSMA/CA system: Impact of imperfect sensing","authors":"J. Chong, Y. Sung, D. Sung","doi":"10.1109/SPAWC.2008.4641577","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641577","url":null,"abstract":"The performance of the carrier sense multiple access/collision avoidance (CSMA/CA) protocol under the presence of carrier sensing errors is analyzed. Two types of carrier sensing errors, false alarm and miss detection, are considered, and their impact on system performance is analyzed using a new CSMA/CA model based on a Markov chain capturing the sensing errors at the physical layer. The throughput as a function of these sensing error probabilities as well as other CSMA/CA parameters is obtained. It is shown that the throughput loss by a poorly chosen sensing threshold is tolerable at intermediate values of the ratio of the packet size to the contention window size, whereas care should be taken in choosing the sensing threshold when the ratio is small or large.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123919836","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641660
A. Beex, T. Ikuma
Recent results show that an adaptive transversal least-mean-square (LMS) equalizer in a narrowband-interference dominated environment operates at a mean weight vector that is different from that of the Wiener equalizer of the same structure. In addition, the time-varying component of the LMS weight vector results in a steady-state mean square error (MSE) that can be substantially lower than that for the fixed Wiener equalizer. However, the MSE for this LMS equalizer is higher than the MSE prediction in which LMS is assumed to be operating in a neighborhood of the Wiener weight vector. We find that -although the transversal LMS equalizer itself does not produce the Wiener weight vector as its steady-state mean - the adaptive algorithm can be modified so that its mean weight vector is the fixed Wiener weight vector, while simultaneously facilitating the time-varying weight behavior that is responsible for the reduction in MSE. The resulting bi-scale LMS (BLMS) algorithm achieves further improvement in MSE.
{"title":"Bi-scale LMS equalization for improved performance","authors":"A. Beex, T. Ikuma","doi":"10.1109/SPAWC.2008.4641660","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641660","url":null,"abstract":"Recent results show that an adaptive transversal least-mean-square (LMS) equalizer in a narrowband-interference dominated environment operates at a mean weight vector that is different from that of the Wiener equalizer of the same structure. In addition, the time-varying component of the LMS weight vector results in a steady-state mean square error (MSE) that can be substantially lower than that for the fixed Wiener equalizer. However, the MSE for this LMS equalizer is higher than the MSE prediction in which LMS is assumed to be operating in a neighborhood of the Wiener weight vector. We find that -although the transversal LMS equalizer itself does not produce the Wiener weight vector as its steady-state mean - the adaptive algorithm can be modified so that its mean weight vector is the fixed Wiener weight vector, while simultaneously facilitating the time-varying weight behavior that is responsible for the reduction in MSE. The resulting bi-scale LMS (BLMS) algorithm achieves further improvement in MSE.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115868075","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641672
G. Fraidenraich, Zhengyuan Xu, S. Rane, J. Cioffi
This paper presents results of ergodic capacity of frequency selective multipath fading channels with path correlations. The exact capacity expression is derived. The main result establishes that, for the uncorrelated case, the ergodic capacity does not depend on either the number of taps or the power delay profile of the channel. However when tap correlation is taken into account, this statement is no longer valid, and high dependence on the channel profile is observed. Although it is impossible to test the impact of different tap correlation models exhaustively, detailed analytical study is carried out under a particular neighbor tap correlation model, i.e., only two neighbor taps are correlated. The worst case that yields the minimal capacity is identified after the intractable and non-convex problem is translated into a convex optimization one. An exact analytical power delay profile for arbitrary number of taps is derived in this case.
{"title":"On capacity of frequency selective multipath channels with path correlations","authors":"G. Fraidenraich, Zhengyuan Xu, S. Rane, J. Cioffi","doi":"10.1109/SPAWC.2008.4641672","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641672","url":null,"abstract":"This paper presents results of ergodic capacity of frequency selective multipath fading channels with path correlations. The exact capacity expression is derived. The main result establishes that, for the uncorrelated case, the ergodic capacity does not depend on either the number of taps or the power delay profile of the channel. However when tap correlation is taken into account, this statement is no longer valid, and high dependence on the channel profile is observed. Although it is impossible to test the impact of different tap correlation models exhaustively, detailed analytical study is carried out under a particular neighbor tap correlation model, i.e., only two neighbor taps are correlated. The worst case that yields the minimal capacity is identified after the intractable and non-convex problem is translated into a convex optimization one. An exact analytical power delay profile for arbitrary number of taps is derived in this case.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121479257","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641671
F. Lima, R.B. dos Santos, F. Cavalcanti, W. Freitas
This paper proposes a time-frequency scheduling algorithm to maximize the satisfaction of users served by an orthogonal frequency division multiple access (OFDMA) system. The satisfaction oriented resource allocation (SORA) algorithm takes into account in its formulation the channel quality, quality of service (QoS) requirements and effect of past allocations, so as to select, in an intelligent way, the set of users that can be more easily satisfied according to the system conditions.
{"title":"Radio resource allocation for maximization of user satisfaction","authors":"F. Lima, R.B. dos Santos, F. Cavalcanti, W. Freitas","doi":"10.1109/SPAWC.2008.4641671","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641671","url":null,"abstract":"This paper proposes a time-frequency scheduling algorithm to maximize the satisfaction of users served by an orthogonal frequency division multiple access (OFDMA) system. The satisfaction oriented resource allocation (SORA) algorithm takes into account in its formulation the channel quality, quality of service (QoS) requirements and effect of past allocations, so as to select, in an intelligent way, the set of users that can be more easily satisfied according to the system conditions.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126089334","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641588
R. D. de Lamare, M. Lowe
This paper presents a low-complexity reduced-rank approach to adaptive linearly constrained minimum variance (LCMV) beamforming. The proposed reduced-rank scheme is based on a constrained joint iterative optimization of adaptive filters according to the minimum variance criterion. The constrained joint iterative optimization procedure adjusts the parameters of a bank of full-rank adaptive filters that forms the projection matrix and an adaptive reduced-rank filter that operates at the output of the bank of filters. We describe LCMV expressions for the design of the projection matrix and the reduced-rank filter and low-complexity stochastic gradient adaptive algorithms for their efficient implementation. Simulations for a beamforming application show that the proposed scheme outperforms in convergence and tracking the state-of-the-art existing reduced-rank schemes with significantly lower complexity.
{"title":"A reduced-rank approach to adaptive linearly constrained minimum variance beamforming based on joint iterative optimization of adaptive filters","authors":"R. D. de Lamare, M. Lowe","doi":"10.1109/SPAWC.2008.4641588","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641588","url":null,"abstract":"This paper presents a low-complexity reduced-rank approach to adaptive linearly constrained minimum variance (LCMV) beamforming. The proposed reduced-rank scheme is based on a constrained joint iterative optimization of adaptive filters according to the minimum variance criterion. The constrained joint iterative optimization procedure adjusts the parameters of a bank of full-rank adaptive filters that forms the projection matrix and an adaptive reduced-rank filter that operates at the output of the bank of filters. We describe LCMV expressions for the design of the projection matrix and the reduced-rank filter and low-complexity stochastic gradient adaptive algorithms for their efficient implementation. Simulations for a beamforming application show that the proposed scheme outperforms in convergence and tracking the state-of-the-art existing reduced-rank schemes with significantly lower complexity.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127112738","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641666
R. Kwak, J. Cioffi
This paper develops the optimal power-allocation algorithm to maximize the sum-rate in orthogonal frequency-division multiple-access (OFDMA) regenerative relaying downlink systems with separate power constraints. The optimal algorithm is based on the Lagrange dual-decomposition method when subchannels are pre-assigned to users and relay stations (RS). This paper also proposes a heuristic algorithm, which performance is exactly the same as that of the optimal algorithm in almost all cases. The simulation results show that OFDMA relaying systems with proposed algorithms outperform the systems without the algorithms by more than 250% and outperform OFDMA systems without RSs by more than 45% when the power of a base station and the power of RSs are optimally adjusted.
{"title":"The optimal power-allocation for OFDMA regenerative relaying downlink systems","authors":"R. Kwak, J. Cioffi","doi":"10.1109/SPAWC.2008.4641666","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641666","url":null,"abstract":"This paper develops the optimal power-allocation algorithm to maximize the sum-rate in orthogonal frequency-division multiple-access (OFDMA) regenerative relaying downlink systems with separate power constraints. The optimal algorithm is based on the Lagrange dual-decomposition method when subchannels are pre-assigned to users and relay stations (RS). This paper also proposes a heuristic algorithm, which performance is exactly the same as that of the optimal algorithm in almost all cases. The simulation results show that OFDMA relaying systems with proposed algorithms outperform the systems without the algorithms by more than 250% and outperform OFDMA systems without RSs by more than 45% when the power of a base station and the power of RSs are optimally adjusted.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125874754","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641613
M. Loiola, R. R. Lopes
In this paper, we propose a semi-blind state-space based receiver that jointly performs channel estimation and data detection in MIMO systems subject to fast frequency-selective fading. To accomplish these two tasks, we first define state equations representing the dynamics of channel and transmitted signals. Then, we obtain the state vector by concatenating the transmitted signals and the channel coefficients. This choice of state vector leads to a nonlinear observation equation and hence to the use of the extended Kalman filter (EKF) to estimate the states variables. We then develop the EKF and show that the proposed receiver is a generalization of many similar receivers for SISO channels. We also develop a reduced complexity version of the proposed algorithm. Simulation results show the performance gains of the proposed receiver when compared to other commonly used receivers.
{"title":"A state-space approach to semi-blind signal detection in fast frequency-selective fading MIMO channels","authors":"M. Loiola, R. R. Lopes","doi":"10.1109/SPAWC.2008.4641613","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641613","url":null,"abstract":"In this paper, we propose a semi-blind state-space based receiver that jointly performs channel estimation and data detection in MIMO systems subject to fast frequency-selective fading. To accomplish these two tasks, we first define state equations representing the dynamics of channel and transmitted signals. Then, we obtain the state vector by concatenating the transmitted signals and the channel coefficients. This choice of state vector leads to a nonlinear observation equation and hence to the use of the extended Kalman filter (EKF) to estimate the states variables. We then develop the EKF and show that the proposed receiver is a generalization of many similar receivers for SISO channels. We also develop a reduced complexity version of the proposed algorithm. Simulation results show the performance gains of the proposed receiver when compared to other commonly used receivers.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125937434","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641639
Y. Nasser, J. Hélard, M. Crussiére, O. Pasquero
This article introduces a 3D space-time-space block code for future terrestrial digital TV in single frequency networks. The proposed 3D code is based on a double layer structure designed for inter-cell and intra-cell space time coded transmissions. We show that this new structure is particularly efficient for SFN environments regardless of the location of the receiver. It is then suitable for fixed, portable and mobile receptions.
{"title":"Efficient 3D space time space block code for future terrestrial digital TV","authors":"Y. Nasser, J. Hélard, M. Crussiére, O. Pasquero","doi":"10.1109/SPAWC.2008.4641639","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641639","url":null,"abstract":"This article introduces a 3D space-time-space block code for future terrestrial digital TV in single frequency networks. The proposed 3D code is based on a double layer structure designed for inter-cell and intra-cell space time coded transmissions. We show that this new structure is particularly efficient for SFN environments regardless of the location of the receiver. It is then suitable for fixed, portable and mobile receptions.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122175070","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 : 2008-07-06DOI: 10.1109/SPAWC.2008.4641664
T. Ben Jabeur, K. Abed-Meraim, H. Boujemaa
In OFDM systems, the inter-symbol interference and inter-block interference are eliminated by using null-tones (NT) and cyclic prefix (CP) redundancy of length higher than the channel size. To preserve a high bit rate, channel shortening method is required to reduce the redundancy. Recently, channel shortening technique with differential encoded OFDM systems without the NT was introduced. This technique is very simple and achieves the channel shortening using only one symbol (the first emitted symbol). In this paper, we prove that, in the presence of null-tones (used in most OFDM-based communication standards), the performance of the previous technique decreases. Therefore, we propose an alternative solution that improves the receiverpsilas performance and preserves a high BER (Bit Error Rate) quality in presence of null-tones.
{"title":"A new blind channel shortening for differential encoded OFDM system","authors":"T. Ben Jabeur, K. Abed-Meraim, H. Boujemaa","doi":"10.1109/SPAWC.2008.4641664","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641664","url":null,"abstract":"In OFDM systems, the inter-symbol interference and inter-block interference are eliminated by using null-tones (NT) and cyclic prefix (CP) redundancy of length higher than the channel size. To preserve a high bit rate, channel shortening method is required to reduce the redundancy. Recently, channel shortening technique with differential encoded OFDM systems without the NT was introduced. This technique is very simple and achieves the channel shortening using only one symbol (the first emitted symbol). In this paper, we prove that, in the presence of null-tones (used in most OFDM-based communication standards), the performance of the previous technique decreases. Therefore, we propose an alternative solution that improves the receiverpsilas performance and preserves a high BER (Bit Error Rate) quality in presence of null-tones.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"109 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126765111","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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