We compare the performance of iterative multi-user successive and parallel decision feedback detectors (DFDs) for code-division multiple access (CDMA). An adaptive successive-DFD (S-DFD) is first presented, which requires only a training sequence and associated timing to estimate all filter coefficients. Simulation results show that with limited training, the adaptive S-DFD performs significantly better than the adaptive parallel-DFD (P-DFD). A large system analysis of error rate for non-adaptive iterative DFDs is also presented, and shows that the S-DFD converges with fewer iterations than the P-DFD.
{"title":"Performance of iterative multiuser decision-feedback receivers","authors":"M. Honig, Yakun Sun","doi":"10.1109/ITW.2001.955126","DOIUrl":"https://doi.org/10.1109/ITW.2001.955126","url":null,"abstract":"We compare the performance of iterative multi-user successive and parallel decision feedback detectors (DFDs) for code-division multiple access (CDMA). An adaptive successive-DFD (S-DFD) is first presented, which requires only a training sequence and associated timing to estimate all filter coefficients. Simulation results show that with limited training, the adaptive S-DFD performs significantly better than the adaptive parallel-DFD (P-DFD). A large system analysis of error rate for non-adaptive iterative DFDs is also presented, and shows that the S-DFD converges with fewer iterations than the P-DFD.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132621944","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}
We consider a relay channel where a relay helps the transmission of messages from one sender to one receiver. The relay is considered not only as a sender that helps the message transmission but as a wire-tapper who can obtain some knowledge about the transmitted messages. In this paper we study the coding problem of the relay channel under the situation that some of transmitted messages are confidential to the relay. A security of such confidential messages is measured by the conditional entropy. We derive an explicit inner bound of the capacity region characterized with the set of transmission rates for which messages are reliably transmitted and the security of confidential messages is larger than a prescribed level.
{"title":"Coding for relay channels with confidential messages","authors":"Y. Oohama","doi":"10.1109/ITW.2001.955145","DOIUrl":"https://doi.org/10.1109/ITW.2001.955145","url":null,"abstract":"We consider a relay channel where a relay helps the transmission of messages from one sender to one receiver. The relay is considered not only as a sender that helps the message transmission but as a wire-tapper who can obtain some knowledge about the transmitted messages. In this paper we study the coding problem of the relay channel under the situation that some of transmitted messages are confidential to the relay. A security of such confidential messages is measured by the conditional entropy. We derive an explicit inner bound of the capacity region characterized with the set of transmission rates for which messages are reliably transmitted and the security of confidential messages is larger than a prescribed level.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134263125","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}
Constrained coding and error-control coding (ECC) are considered in a combined framework. In the context of soft iterative decoding, this allows the ECC decoder (e.g., for a turbo or LDPC code) to gain direct access to the probabilities from the channel decoder. In addition, a soft decoder for the constraint can be introduced to yield additional coding gain. Practical methods for combining the constraint and ECC include a modified concatenation scheme and a bit insertion scheme.
{"title":"Constrained coding and soft iterative decoding","authors":"J. L. Fan","doi":"10.1109/ITW.2001.955122","DOIUrl":"https://doi.org/10.1109/ITW.2001.955122","url":null,"abstract":"Constrained coding and error-control coding (ECC) are considered in a combined framework. In the context of soft iterative decoding, this allows the ECC decoder (e.g., for a turbo or LDPC code) to gain direct access to the probabilities from the channel decoder. In addition, a soft decoder for the constraint can be introduced to yield additional coding gain. Practical methods for combining the constraint and ECC include a modified concatenation scheme and a bit insertion scheme.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133910068","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}
Many decoding algorithms need to compute some lists of binary vectors that minimize a given weight function. Furthermore, it is often desirable that these vectors are generated by increasing weight. The considered weight function is usually decreasing in the a priori likelihood that the vector yields correct decoding. We present a new technique to generate candidates for error patterns from the most a priori likely to the least, that proves significantly more efficient than any other known method.
{"title":"Generation of binary vectors that optimize a given weight function with application to soft-decision decoding","authors":"A. Valembois, M. Fossorier","doi":"10.1109/ITW.2001.955163","DOIUrl":"https://doi.org/10.1109/ITW.2001.955163","url":null,"abstract":"Many decoding algorithms need to compute some lists of binary vectors that minimize a given weight function. Furthermore, it is often desirable that these vectors are generated by increasing weight. The considered weight function is usually decreasing in the a priori likelihood that the vector yields correct decoding. We present a new technique to generate candidates for error patterns from the most a priori likely to the least, that proves significantly more efficient than any other known method.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116115060","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}
We consider multiple antenna systems in which a large number of antennas occupy a given physical volume. In this regime the assumptions of the standard models of multiple antennas systems become questionable. We show that for such spatially dense multiple antenna systems one should expect the behavior of the capacity to be qualitatively different than what the standard multiple antenna models predict.
{"title":"Dense multiple antenna systems","authors":"N. Chiurtu, B. Rimoldi, E. Telatar","doi":"10.1109/ITW.2001.955153","DOIUrl":"https://doi.org/10.1109/ITW.2001.955153","url":null,"abstract":"We consider multiple antenna systems in which a large number of antennas occupy a given physical volume. In this regime the assumptions of the standard models of multiple antennas systems become questionable. We show that for such spatially dense multiple antenna systems one should expect the behavior of the capacity to be qualitatively different than what the standard multiple antenna models predict.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122748760","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}
The BCJR algorithm consists of two linear recursions whose joint transient response define the algorithm's response to errors. The transient behavior is described and some implications are discussed for sliding block decoder storage, recovery from incorrect starts, and good code design.
{"title":"Transient and convergence properties of the BCJR decoder via a linear system model","authors":"John B. Anderson","doi":"10.1109/ITW.2001.955162","DOIUrl":"https://doi.org/10.1109/ITW.2001.955162","url":null,"abstract":"The BCJR algorithm consists of two linear recursions whose joint transient response define the algorithm's response to errors. The transient behavior is described and some implications are discussed for sliding block decoder storage, recovery from incorrect starts, and good code design.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129903569","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}
There are several cases where the maximum free distance (MFD) time-invariant convolutional code of a given rate and total encoder memory does not meet the Heller bound or where the encoder that does meet the Heller bound is catastrophic. In order to find codes that meet the Heller bound, it is sometimes necessary to use time-varying convolutional codes. Some periodic time-varying convolutional codes with free distance greater than the best known time-invariant code of the same rate and total encoder memory are presented. These codes also achieve the Heller bound for the given code parameters. In addition, the use of time-varying encoders in order to achieve "spectral thinning" is explored.
{"title":"Time varying convolutional codes revisited","authors":"L. C. Pérez","doi":"10.1109/ITW.2001.955138","DOIUrl":"https://doi.org/10.1109/ITW.2001.955138","url":null,"abstract":"There are several cases where the maximum free distance (MFD) time-invariant convolutional code of a given rate and total encoder memory does not meet the Heller bound or where the encoder that does meet the Heller bound is catastrophic. In order to find codes that meet the Heller bound, it is sometimes necessary to use time-varying convolutional codes. Some periodic time-varying convolutional codes with free distance greater than the best known time-invariant code of the same rate and total encoder memory are presented. These codes also achieve the Heller bound for the given code parameters. In addition, the use of time-varying encoders in order to achieve \"spectral thinning\" is explored.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128538718","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}
Summary form only given. We address the capacity problem for a class of time-varying multiple-access channels (TVMAC), when the underlying channel state evolves in time according to a probability law which is known to the transmitters and the receiver. Additionally, the transmitters and the receiver have access to varying degrees of channel state information (CSI) concerning the condition of the channel. Discrete-time channels with finite input, output and state alphabets are considered first. The special case of a memoryless TVMAC, with the channel state process being a time-invariant, indecomposable, aperiodic Markov chain, shows a surprising anomaly in that imperfect transmitter CSI can cause the capacity under some distributions for the initial state to be strictly larger than that under a stationary distribution for the initial state. We also consider a time-varying multiple-access fading channel with additive Gaussian noise, when various amounts of CSI are provided to the transmitters and perfect CSI is available to the receiver, and the fades are assumed to be stationary and ergodic. Implications for transmitter power control are discussed.
{"title":"Capacities of time-varying multiple-access channels with side information","authors":"A. Das, P. Narayan","doi":"10.1109/ITW.2001.955152","DOIUrl":"https://doi.org/10.1109/ITW.2001.955152","url":null,"abstract":"Summary form only given. We address the capacity problem for a class of time-varying multiple-access channels (TVMAC), when the underlying channel state evolves in time according to a probability law which is known to the transmitters and the receiver. Additionally, the transmitters and the receiver have access to varying degrees of channel state information (CSI) concerning the condition of the channel. Discrete-time channels with finite input, output and state alphabets are considered first. The special case of a memoryless TVMAC, with the channel state process being a time-invariant, indecomposable, aperiodic Markov chain, shows a surprising anomaly in that imperfect transmitter CSI can cause the capacity under some distributions for the initial state to be strictly larger than that under a stationary distribution for the initial state. We also consider a time-varying multiple-access fading channel with additive Gaussian noise, when various amounts of CSI are provided to the transmitters and perfect CSI is available to the receiver, and the fades are assumed to be stationary and ergodic. Implications for transmitter power control are discussed.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132060286","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}
A simple multi-cell Rayleigh fading uplink communication model is suggested and analyzed for optimally coded randomly spread DS-CDMA with multiuser detection. The model adheres to Wyner's (1994) infinite linear cell-array setting, according to which only adjacent-cell interference is present, and characterized by a single parameter 0/spl les//spl alpha//spl les/1. The discussion is confined to asymptotic analysis where both the number of users per cell and the processing gain go to infinity, while their ratio goes to some finite constant. The spectral efficiency of various multiuser detection strategies is evaluated assuming single cell-site processing, and equal transmit powers for all users in all cells. Comparative results demonstrate how performance is affected by the introduction of inter-cell interference (with and without fading), and what is the penalty associated with the randomly spread coded DS-CDMA strategy.
{"title":"Random CDMA in the multiple cell uplink environment: the effect of fading on various receivers","authors":"B. M. Zaidel, S. Shamai, S. Verdú","doi":"10.1109/ITW.2001.955130","DOIUrl":"https://doi.org/10.1109/ITW.2001.955130","url":null,"abstract":"A simple multi-cell Rayleigh fading uplink communication model is suggested and analyzed for optimally coded randomly spread DS-CDMA with multiuser detection. The model adheres to Wyner's (1994) infinite linear cell-array setting, according to which only adjacent-cell interference is present, and characterized by a single parameter 0/spl les//spl alpha//spl les/1. The discussion is confined to asymptotic analysis where both the number of users per cell and the processing gain go to infinity, while their ratio goes to some finite constant. The spectral efficiency of various multiuser detection strategies is evaluated assuming single cell-site processing, and equal transmit powers for all users in all cells. Comparative results demonstrate how performance is affected by the introduction of inter-cell interference (with and without fading), and what is the penalty associated with the randomly spread coded DS-CDMA strategy.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129252620","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}
The design of uniquely decodable DC-free multi-user coding schemes with good rate sums for the multiple access adder channel is described in this paper. It is shown that by using the direct sum construction on short multi-user codes, it is possible to devise longer DC-free multi-user coding schemes with rate sums which increase quite rapidly at each iteration of the construction. Asymptotically, there is no penalty in requiring the coding schemes to be DC-free. In addition, the schemes can be efficiently soft decision decoded using a relatively low complexity sectionalised trellis.
{"title":"Direct sum construction of DC-free adder channel codes","authors":"Phillip Benachour, P. Farrell, B. Honary","doi":"10.1109/ITW.2001.955148","DOIUrl":"https://doi.org/10.1109/ITW.2001.955148","url":null,"abstract":"The design of uniquely decodable DC-free multi-user coding schemes with good rate sums for the multiple access adder channel is described in this paper. It is shown that by using the direct sum construction on short multi-user codes, it is possible to devise longer DC-free multi-user coding schemes with rate sums which increase quite rapidly at each iteration of the construction. Asymptotically, there is no penalty in requiring the coding schemes to be DC-free. In addition, the schemes can be efficiently soft decision decoded using a relatively low complexity sectionalised trellis.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115211026","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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