Pub Date : 2008-07-06DOI: 10.1109/SPAWC.2008.4641567
Xiaolu Zhang, M. Tao, C. Ng
Energy efficient transmission is of vital importance in the design of wireless sensor networks (WSN).Minimizing the sum of energy consumption of all sensor nodes in the network may lead to some nodes with non-rechargeable batteries running out of energy quickly. In this paper, we consider to maximize the time until the first node fails in the network, namely, the network lifetime. Transmission schemes in a WSN where multiple sensors observe a common physical phenomenon are investigated. We show that the optimal joint time and power control (JTPC) takes advantage of ldquolazy schedulingrdquo and ldquoopportunistic quantizationrdquo. We then demonstrate that the JTPC can be implemented in a partially distributed manner. Numerical results show that significant lifetime gain can be achieved when compared with existing scheduling algorithms.
{"title":"Maximum lifetime transmission in wireless sensor networks for a common source observation","authors":"Xiaolu Zhang, M. Tao, C. Ng","doi":"10.1109/SPAWC.2008.4641567","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641567","url":null,"abstract":"Energy efficient transmission is of vital importance in the design of wireless sensor networks (WSN).Minimizing the sum of energy consumption of all sensor nodes in the network may lead to some nodes with non-rechargeable batteries running out of energy quickly. In this paper, we consider to maximize the time until the first node fails in the network, namely, the network lifetime. Transmission schemes in a WSN where multiple sensors observe a common physical phenomenon are investigated. We show that the optimal joint time and power control (JTPC) takes advantage of ldquolazy schedulingrdquo and ldquoopportunistic quantizationrdquo. We then demonstrate that the JTPC can be implemented in a partially distributed manner. Numerical results show that significant lifetime gain can be achieved when compared with existing scheduling algorithms.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"77 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":"115936222","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.2008.4641605
C. Mosquera, Roberto López-Valcarce, S. Jayaweera
Distributed estimation and detection is of interest for those situations for which the sensor net must achieve an agreement by exchanging information without resorting to the use of an external fusion center. In this paper we deal with the distributed estimation of a static parameter which has been initially estimated by a set of sensors, and for which it is important to have similar estimates as accurate as possible. The cooperation is performed in a distributed way to guarantee scalability and robustness to failures, and it is designed to reduce the detrimental effects of the channel noise on the sensor exchanges. We pose a general framework to include the most relevant contributions dealing with this type of channel imperfection, so pros and cons can be discussed on common ground.
{"title":"Distributed estimation with noisy exchanges","authors":"C. Mosquera, Roberto López-Valcarce, S. Jayaweera","doi":"10.1109/SPAWC.2008.4641605","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641605","url":null,"abstract":"Distributed estimation and detection is of interest for those situations for which the sensor net must achieve an agreement by exchanging information without resorting to the use of an external fusion center. In this paper we deal with the distributed estimation of a static parameter which has been initially estimated by a set of sensors, and for which it is important to have similar estimates as accurate as possible. The cooperation is performed in a distributed way to guarantee scalability and robustness to failures, and it is designed to reduce the detrimental effects of the channel noise on the sensor exchanges. We pose a general framework to include the most relevant contributions dealing with this type of channel imperfection, so pros and cons can be discussed on common ground.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"28 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":"116894183","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.2008.4641681
A. Guimarães, E. Pinto
We use the particle filtering approach to develop a new Bayesian equalizer for turbo equalization under conditions of imperfect estimation of the channel impulse response (CIR) and the noise variance. This new equalizer is derived on the basis of fixed-lag smoothing, using the SIS (Sequential Importance Sampling) methodology to approximate the conditional probability distribution of a block of transmitted symbols, given the corresponding block of channel outputs and the estimates of the unknown parameters (channel gains and noise variance). Simulation results of performance evaluation and comparison with the MMSE equalizer proposed in [1] are provided, under different conditions of errors in the estimation of the mentioned parameters. It is shown that the proposed scheme significantly outperforms the SISO (soft-input soft-output) equalizer of [1], specially when the estimation errors are more significant.
{"title":"Particle filtering applied to turbo equalization with channel and noise variance estimation","authors":"A. Guimarães, E. Pinto","doi":"10.1109/SPAWC.2008.4641681","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641681","url":null,"abstract":"We use the particle filtering approach to develop a new Bayesian equalizer for turbo equalization under conditions of imperfect estimation of the channel impulse response (CIR) and the noise variance. This new equalizer is derived on the basis of fixed-lag smoothing, using the SIS (Sequential Importance Sampling) methodology to approximate the conditional probability distribution of a block of transmitted symbols, given the corresponding block of channel outputs and the estimates of the unknown parameters (channel gains and noise variance). Simulation results of performance evaluation and comparison with the MMSE equalizer proposed in [1] are provided, under different conditions of errors in the estimation of the mentioned parameters. It is shown that the proposed scheme significantly outperforms the SISO (soft-input soft-output) equalizer of [1], specially when the estimation errors are more significant.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"196 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":"116675510","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.2008.4641651
A. Das, B. Rao
Multiple antenna enhancements via symbol timing relative offsets (MAESTRO) was recently introduced as a scheme to improve the performance of a V-BLAST like multi-antenna system by introducing sub-symbol timing offsets between the transmit antennas. In this paper we address the role of receiver structure on performance and investigate the optimal choice of the time offset parameter. A similar timing offset V-BLAST scheme was also introduced by Shao et al., where the authors use a zero-forcing (ZF) receiver and conclude the system outperforms V-BLAST only for small block sizes. We show that the zero-forcing (ZF) receiver suggested by Shao et al. is deficient and is the main reason for some of the drawbacks observed by them. The optimal ZF receiver is derived, and along with the linear MMSE receiver, is shown to exhibit no such weaknesses. The problem of optimal offset is also examined and the optimal offset for a 2 times 2 MIMO system derived.
{"title":"Impact of receiver structure and timing offset on MIMO spatial multiplexing","authors":"A. Das, B. Rao","doi":"10.1109/SPAWC.2008.4641651","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641651","url":null,"abstract":"Multiple antenna enhancements via symbol timing relative offsets (MAESTRO) was recently introduced as a scheme to improve the performance of a V-BLAST like multi-antenna system by introducing sub-symbol timing offsets between the transmit antennas. In this paper we address the role of receiver structure on performance and investigate the optimal choice of the time offset parameter. A similar timing offset V-BLAST scheme was also introduced by Shao et al., where the authors use a zero-forcing (ZF) receiver and conclude the system outperforms V-BLAST only for small block sizes. We show that the zero-forcing (ZF) receiver suggested by Shao et al. is deficient and is the main reason for some of the drawbacks observed by them. The optimal ZF receiver is derived, and along with the linear MMSE receiver, is shown to exhibit no such weaknesses. The problem of optimal offset is also examined and the optimal offset for a 2 times 2 MIMO system derived.","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":"127427803","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.2008.4641665
M.S. Al Bashar, Z. Ding, Y. Li
We consider a heterogeneous multiuser OFDM wireless network serving both QoS constrained high-priority users and best-effort users. We investigate resource allocation to maximize the total network utility by specifying two different utility functions for the two user classes. Our strategy is to first maximize the number of satisfied high-priority users before allocating the remaining resource among the best-effort users. Our results show significant improvement of overall user satisfaction among both user classes.
{"title":"QOS aware resource allocation for heterogeneous multiuser OFDM wireless networks","authors":"M.S. Al Bashar, Z. Ding, Y. Li","doi":"10.1109/SPAWC.2008.4641665","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641665","url":null,"abstract":"We consider a heterogeneous multiuser OFDM wireless network serving both QoS constrained high-priority users and best-effort users. We investigate resource allocation to maximize the total network utility by specifying two different utility functions for the two user classes. Our strategy is to first maximize the number of satisfied high-priority users before allocating the remaining resource among the best-effort users. Our results show significant improvement of overall user satisfaction among both user classes.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"47 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":"126126874","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.2008.4641625
A. Ho, M. Boucheret, N. Thomas, M. Dervin, X. Deplancq
This paper proposes an OFDM receiver for the forward link of a fixed broadband satellite system. Although the satellite channel is not frequency selective, OFDM could be preferred to single carrier waveforms if it allows to improve the system spectral efficiency. The possible gain would arise from the possibility to reduce the overhead in a non-frequency selective channel. The cyclic prefix, introduced to suppress inter symbol interference (ISI), or the pilots used to estimate the channel, are not necessary in such context. Nevertheless, a part of the overhead in OFDM-based systems is necessary for synchronization purposes. This paper focuses on this problem. We propose a complete synchronization structure essentially based on a non pilot aided algorithm, only requiring some reduced overhead for a first coarse synchronization stage. The performance of the proposed receiver is assessed through simulation results.
{"title":"OFDM synchronization scheme for the forward link of a fixed broadband satellite system","authors":"A. Ho, M. Boucheret, N. Thomas, M. Dervin, X. Deplancq","doi":"10.1109/SPAWC.2008.4641625","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641625","url":null,"abstract":"This paper proposes an OFDM receiver for the forward link of a fixed broadband satellite system. Although the satellite channel is not frequency selective, OFDM could be preferred to single carrier waveforms if it allows to improve the system spectral efficiency. The possible gain would arise from the possibility to reduce the overhead in a non-frequency selective channel. The cyclic prefix, introduced to suppress inter symbol interference (ISI), or the pilots used to estimate the channel, are not necessary in such context. Nevertheless, a part of the overhead in OFDM-based systems is necessary for synchronization purposes. This paper focuses on this problem. We propose a complete synchronization structure essentially based on a non pilot aided algorithm, only requiring some reduced overhead for a first coarse synchronization stage. The performance of the proposed receiver is assessed through simulation results.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"74 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":"121028167","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.2008.4641597
S. Chatzinotas, Muhammad Ali Imran, C. Tzaras
The majority of information-theoretic hyper-receiver cellular models preserve a fundamental assumption which has initially appeared in Wynerpsilas [1] model, namely the collocation of user terminals (UTs). Although this assumption produces more tractable mathematical models, it is unrealistic with respect to current practical cellular systems. In this paper, we alleviate this assumption by assuming uniformly distributed UTs. The model under investigation is a Gaussian cellular multiple access channel (GCMAC) over a planar cellular array in the presence of power-law path loss and flat fading. In this context, we evaluate the effect of UT distribution on the optimal sum-rate capacity by considering a variable-density cellular system. Furthermore, we compare the sum-rate capacity produced by the planar and the linear cellular array. Finally, the analytical results are interpreted in the context of a typical macrocellular scenario.
{"title":"Optimal information theoretic capacity of the planar cellular uplink channel","authors":"S. Chatzinotas, Muhammad Ali Imran, C. Tzaras","doi":"10.1109/SPAWC.2008.4641597","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641597","url":null,"abstract":"The majority of information-theoretic hyper-receiver cellular models preserve a fundamental assumption which has initially appeared in Wynerpsilas [1] model, namely the collocation of user terminals (UTs). Although this assumption produces more tractable mathematical models, it is unrealistic with respect to current practical cellular systems. In this paper, we alleviate this assumption by assuming uniformly distributed UTs. The model under investigation is a Gaussian cellular multiple access channel (GCMAC) over a planar cellular array in the presence of power-law path loss and flat fading. In this context, we evaluate the effect of UT distribution on the optimal sum-rate capacity by considering a variable-density cellular system. Furthermore, we compare the sum-rate capacity produced by the planar and the linear cellular array. Finally, the analytical results are interpreted in the context of a typical macrocellular scenario.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"68 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":"128163110","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.2008.4641589
Ciou-Ping Wu, Jen-Ming Wu
Spatial multiplexing is a common technique for multiple-input multiple-output (MIMO) communications that independent information streams are sent over different antennas. The precoder design based on the channel state information (CSI) can process the transmitting symbol before transmission. However, the spatial multiplexing is still sensitive to the ill-conditioning of the channel matrix. The conventional beam directions in the precoder are designed via singular value decomposition (SVD) which diagonalize the MIMO channel matrix H into eigenmodes. In this paper, we present a different approach using LU decomposition (LUD) to obtain the beam directions. We show that the LUD yields better channel condition and hence better error performance. The LUD-based precoder also has less feedback channel bandwidth requirement and lower complexity than the conventional SVD-based precoder.
{"title":"Low complexity channel decomposition for spatial multiplexing MIMO systems","authors":"Ciou-Ping Wu, Jen-Ming Wu","doi":"10.1109/SPAWC.2008.4641589","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641589","url":null,"abstract":"Spatial multiplexing is a common technique for multiple-input multiple-output (MIMO) communications that independent information streams are sent over different antennas. The precoder design based on the channel state information (CSI) can process the transmitting symbol before transmission. However, the spatial multiplexing is still sensitive to the ill-conditioning of the channel matrix. The conventional beam directions in the precoder are designed via singular value decomposition (SVD) which diagonalize the MIMO channel matrix H into eigenmodes. In this paper, we present a different approach using LU decomposition (LUD) to obtain the beam directions. We show that the LUD yields better channel condition and hence better error performance. The LUD-based precoder also has less feedback channel bandwidth requirement and lower complexity than the conventional SVD-based precoder.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"67 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":"121572928","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.2008.4641677
D. Gregoratti, X. Mestre
This paper considers a DS/CDMA relay system where random spreading sequences are employed at the relays to allow multiple access to the channel between relays and destination. Two different protocols are considered and compared, the difference between them being whether the source remains silent or sends new information symbols during the relaying. For both protocols, we provide a low source power approximation for the spectral efficiency when employing, at the destination, either the optimal or the linear minimum mean square error receiver. The new expression is studied for the single relay case to identify under which conditions relaying results convenient over direct source-destination communication. Furthermore, we investigate the optimum percentage of relaying time in order to maximize the global spectral efficiency.
{"title":"On the lowsource power regime of the DS/CDMA relay channel","authors":"D. Gregoratti, X. Mestre","doi":"10.1109/SPAWC.2008.4641677","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641677","url":null,"abstract":"This paper considers a DS/CDMA relay system where random spreading sequences are employed at the relays to allow multiple access to the channel between relays and destination. Two different protocols are considered and compared, the difference between them being whether the source remains silent or sends new information symbols during the relaying. For both protocols, we provide a low source power approximation for the spectral efficiency when employing, at the destination, either the optimal or the linear minimum mean square error receiver. The new expression is studied for the single relay case to identify under which conditions relaying results convenient over direct source-destination communication. Furthermore, we investigate the optimum percentage of relaying time in order to maximize the global spectral efficiency.","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":"131752903","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.2008.4641650
Junwei Zhang, M. C. Gursoy
In this paper, communication over imperfectly-known fading channels with different degrees of cooperation is studied. The three-node relay channel is considered. It is assumed that communication starts with the network training phase in which the receivers estimate the fading coefficients of their respective channels. In the data transmission phase, amplify-and-forward and decode-and-forward relaying schemes are employed. For different cooperation protocols, achievable rate expressions are obtained. These achievable rate expressions are then used to find the optimal resource allocation strategies. In particular, the fraction of total time or bandwidth that needs to be allocated to the relay for best performance is identified. Under a total power constraint, optimal allocation of power between the source and relay is investigated. Finally, bit energy requirements in the low-power regime are studied.
{"title":"To Cooperate, or not to cooperate in imperfectly-known fading channels","authors":"Junwei Zhang, M. C. Gursoy","doi":"10.1109/SPAWC.2008.4641650","DOIUrl":"https://doi.org/10.1109/SPAWC.2008.4641650","url":null,"abstract":"In this paper, communication over imperfectly-known fading channels with different degrees of cooperation is studied. The three-node relay channel is considered. It is assumed that communication starts with the network training phase in which the receivers estimate the fading coefficients of their respective channels. In the data transmission phase, amplify-and-forward and decode-and-forward relaying schemes are employed. For different cooperation protocols, achievable rate expressions are obtained. These achievable rate expressions are then used to find the optimal resource allocation strategies. In particular, the fraction of total time or bandwidth that needs to be allocated to the relay for best performance is identified. Under a total power constraint, optimal allocation of power between the source and relay is investigated. Finally, bit energy requirements in the low-power regime are studied.","PeriodicalId":197154,"journal":{"name":"2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications","volume":"97 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":"131149242","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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