Recent research activities in the area of mobile radio communications have moved to third generation (3G) cellular systems to achieve higher quality with variable transmission rate of multimedia information. In this paper, an overview is presented of various interference cancellation and iterative detection techniques that are believed to be suitable for 3G wireless communications systems. Key concepts are space-time processing and space-division multiple access (or SDMA) techniques. SDMA techniques are possible with software antennas. Furthermore, to reduce receiver implementation complexity, iterative detection techniques are considered. A particularly attractive method uses tentative hard decisions, made on the received positions with the highest reliability, according to some criterion, and can potentially yield an important reduction in the computational requirements of an iterative receiver, with minimum penalty in error performance. A study of the tradeoffs between complexity and performance loss of iterative multiuser detection techniques is a good research topic.
{"title":"On interference cancellation and iterative techniques","authors":"R. Kohno, R. Morelos-Zaragoza","doi":"10.1109/ITW.2001.955129","DOIUrl":"https://doi.org/10.1109/ITW.2001.955129","url":null,"abstract":"Recent research activities in the area of mobile radio communications have moved to third generation (3G) cellular systems to achieve higher quality with variable transmission rate of multimedia information. In this paper, an overview is presented of various interference cancellation and iterative detection techniques that are believed to be suitable for 3G wireless communications systems. Key concepts are space-time processing and space-division multiple access (or SDMA) techniques. SDMA techniques are possible with software antennas. Furthermore, to reduce receiver implementation complexity, iterative detection techniques are considered. A particularly attractive method uses tentative hard decisions, made on the received positions with the highest reliability, according to some criterion, and can potentially yield an important reduction in the computational requirements of an iterative receiver, with minimum penalty in error performance. A study of the tradeoffs between complexity and performance loss of iterative multiuser detection techniques is a good research topic.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"71 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":"127397924","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 the design of robust codes that exploit both space and time diversity, using bit-interleaved coded modulation. Under quasi-static fading conditions, codes constructed in this way achieve full diversity and perform close to the best space-time trellis codes of comparable complexity. Under fast-fading conditions, these same codes achieve higher diversity than previously known codes of the same complexity.
{"title":"Robust space-time codes for time-selective fading","authors":"Z. Hong, B. Hughes","doi":"10.1109/ITW.2001.955155","DOIUrl":"https://doi.org/10.1109/ITW.2001.955155","url":null,"abstract":"We consider the design of robust codes that exploit both space and time diversity, using bit-interleaved coded modulation. Under quasi-static fading conditions, codes constructed in this way achieve full diversity and perform close to the best space-time trellis codes of comparable complexity. Under fast-fading conditions, these same codes achieve higher diversity than previously known codes of the same complexity.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"21 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":"126811137","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}
In a previous paper we proposed a multiuser space-time modulation scheme that leverages single-user space-time constellations and guarantees both, a full diversity order, as well as an asymptotic (high SNR) single-user like performance for every user. This is achieved by multiplying each user's space-time information matrix symbol by a low-dimensional "spreading matrix." For instance, for N/sub T/-transmit antennas per user and if the single-user space-time constellation employed requires only the minimum dimension N/sub T/, no more than N/sub T/+1 dimensions are required for the common signal space of all users, i.e., each user's spreading matrix is of size (N/sub T/+1)/spl times/N/sub T/, independent of the number of users. In this paper, we present a simplified design criterion to obtain these spreading matrices by numerical optimization. Since the columns of each user's spreading matrix are constrained to be orthonormal, we propose to perform the optimization using a parameterization of the Grassmann manifold. A special feature of the simplified criterion, and thus of the resulting spreading matrices, is that they are independent of the particular single-user space-time constellations (of a given dimension), so that different spectral efficiencies can be attained without changing or redesigning the spreading matrices.
{"title":"Low-dimensional spreading matrices for multiuser space-time modulation","authors":"M. Brehler, M. Varanasi","doi":"10.1109/ITW.2001.955133","DOIUrl":"https://doi.org/10.1109/ITW.2001.955133","url":null,"abstract":"In a previous paper we proposed a multiuser space-time modulation scheme that leverages single-user space-time constellations and guarantees both, a full diversity order, as well as an asymptotic (high SNR) single-user like performance for every user. This is achieved by multiplying each user's space-time information matrix symbol by a low-dimensional \"spreading matrix.\" For instance, for N/sub T/-transmit antennas per user and if the single-user space-time constellation employed requires only the minimum dimension N/sub T/, no more than N/sub T/+1 dimensions are required for the common signal space of all users, i.e., each user's spreading matrix is of size (N/sub T/+1)/spl times/N/sub T/, independent of the number of users. In this paper, we present a simplified design criterion to obtain these spreading matrices by numerical optimization. Since the columns of each user's spreading matrix are constrained to be orthonormal, we propose to perform the optimization using a parameterization of the Grassmann manifold. A special feature of the simplified criterion, and thus of the resulting spreading matrices, is that they are independent of the particular single-user space-time constellations (of a given dimension), so that different spectral efficiencies can be attained without changing or redesigning the spreading matrices.","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":"128868472","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}
In 1998, Hagenauer and Loeliger et al. independently proposed to decode error correcting codes by analog electronic networks. In contrast to previous work on analog Viterbi decoders, the work both by Hagenauer and by Loeliger et al. was inspired by turbo-style decoding of codes described by graphs. Large gains, in terms of speed or power consumption, over digital implementations were envisaged. Since 1998, much effort has been spent towards turning these ideas into working chips. While only decoders of "toy" codes have so far been successfully manufactured, extensive simulations of such circuits have not revealed any fundamental problems. Some progress has also been made in analyzing the effects of transistor mismatch. While much remains to be learned, the author feels confident that analog decoders will eventually find their way into applications. The present paper, rather than reporting on circuit details, offers some thoughts on "the bigger picture"- the underlying principles, motivations, and possible directions of future research.
{"title":"Analog decoding and beyond","authors":"Hans-Andrea Loeliger","doi":"10.1109/ITW.2001.955159","DOIUrl":"https://doi.org/10.1109/ITW.2001.955159","url":null,"abstract":"In 1998, Hagenauer and Loeliger et al. independently proposed to decode error correcting codes by analog electronic networks. In contrast to previous work on analog Viterbi decoders, the work both by Hagenauer and by Loeliger et al. was inspired by turbo-style decoding of codes described by graphs. Large gains, in terms of speed or power consumption, over digital implementations were envisaged. Since 1998, much effort has been spent towards turning these ideas into working chips. While only decoders of \"toy\" codes have so far been successfully manufactured, extensive simulations of such circuits have not revealed any fundamental problems. Some progress has also been made in analyzing the effects of transistor mismatch. While much remains to be learned, the author feels confident that analog decoders will eventually find their way into applications. The present paper, rather than reporting on circuit details, offers some thoughts on \"the bigger picture\"- the underlying principles, motivations, and possible directions of future research.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"11 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120903664","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 examine a multiple-access AWGN channel with synchronous DS-CDMA in which the channel amplitude and noise variance parameters are unknown a priori. We derive an iterative joint multiuser decoder and parameter estimator based on soft interference cancellation and on soft decision-driven least-squares estimation. Our derivation is obtained by applying the sum-product algorithm to the factor graph of the joint a posteriori probability measure of the information bits and of the unknown channel parameters.
{"title":"Iterative multiuser joint detection and parameter estimation: a factor-graph approach","authors":"G. Caire, A. Tulino, E. Biglieri","doi":"10.1109/ITW.2001.955128","DOIUrl":"https://doi.org/10.1109/ITW.2001.955128","url":null,"abstract":"We examine a multiple-access AWGN channel with synchronous DS-CDMA in which the channel amplitude and noise variance parameters are unknown a priori. We derive an iterative joint multiuser decoder and parameter estimator based on soft interference cancellation and on soft decision-driven least-squares estimation. Our derivation is obtained by applying the sum-product algorithm to the factor graph of the joint a posteriori probability measure of the information bits and of the unknown channel parameters.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"130 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":"124275748","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}
An investigation of unequal error protection (UEP) methods applied to JPEG image transmission using turbo codes is presented. The JPEG image is partitioned into two groups, i.e., DC components and AC components according to their respective sensitivity to channel noise. The highly sensitive DC components are better protected with a lower coding rate, while the less sensitive AC components use a higher coding rate. Simulation results are given to demonstrate how the UEP schemes outperforms the equal error protection (EEP) scheme in terms of bit error rate (BER) and peak signal to noise ratio (PSNR).
{"title":"Unequal error protection applied to JPEG image transmission using turbo codes","authors":"W. Xiang, S. A. Barbulescu, S. S. Pietrobon","doi":"10.1109/ITW.2001.955137","DOIUrl":"https://doi.org/10.1109/ITW.2001.955137","url":null,"abstract":"An investigation of unequal error protection (UEP) methods applied to JPEG image transmission using turbo codes is presented. The JPEG image is partitioned into two groups, i.e., DC components and AC components according to their respective sensitivity to channel noise. The highly sensitive DC components are better protected with a lower coding rate, while the less sensitive AC components use a higher coding rate. Simulation results are given to demonstrate how the UEP schemes outperforms the equal error protection (EEP) scheme in terms of bit error rate (BER) and peak signal to noise ratio (PSNR).","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"115 2 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":"121266085","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}
Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. It is shown that the code performance is dominated by the minimum rank r and the minimum determinant of the codeword distance matrix when the product of the minimum rank r and the number of receive antennas n/sub R/ is less than 4. However, when r/spl middot/n/sub R/ is greater than or equal to 4, the code error performance is dominated by the minimum trace of the codeword distance matrix. Furthermore, we present recursive spacetime trellis coded modulation (STTC) which outperforms feedforward STTC on slow and fast fading channels. A substantial increase in performance can be obtained by constructing spacetime turbo trellis coded modulation (ST turbo TCM) which consists of concatenated recursive STTC, decoded by iterative decoding algorithm. The proposed recursive STTC are used as constituent codes in this scheme. The proposed ST turbo TCM significantly outperforms the best known STTC on both slow and fast fading channels.
提出了一种新的慢瑞利衰落信道空时码设计准则。结果表明，当最小秩r与接收天线数n/sub r /的乘积小于4时，编码性能受最小秩r和码字距离矩阵的最小行列式的支配。然而，当r/spl中点/n/下标r/大于等于4时，码字距离矩阵的最小迹线主导码错性能。此外，我们提出了递归时空网格编码调制(STTC)，它在慢速和快速衰落信道上优于前馈STTC。通过构建由串联递归STTC组成的时空turbo栅格编码调制(ST turbo TCM)，采用迭代译码算法进行解码，可以大幅提高性能。在该方案中，采用所提出的递归STTC作为组成码。所提出的ST turbo TCM在慢速和快速衰落信道上都明显优于最著名的STTC。
{"title":"Design of space-time turbo TCM on fading channels","authors":"Jinhong Yuan, B. Vucetic, Zhuo Chen, W. Firmanto","doi":"10.1109/ITW.2001.955158","DOIUrl":"https://doi.org/10.1109/ITW.2001.955158","url":null,"abstract":"Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. It is shown that the code performance is dominated by the minimum rank r and the minimum determinant of the codeword distance matrix when the product of the minimum rank r and the number of receive antennas n/sub R/ is less than 4. However, when r/spl middot/n/sub R/ is greater than or equal to 4, the code error performance is dominated by the minimum trace of the codeword distance matrix. Furthermore, we present recursive spacetime trellis coded modulation (STTC) which outperforms feedforward STTC on slow and fast fading channels. A substantial increase in performance can be obtained by constructing spacetime turbo trellis coded modulation (ST turbo TCM) which consists of concatenated recursive STTC, decoded by iterative decoding algorithm. The proposed recursive STTC are used as constituent codes in this scheme. The proposed ST turbo TCM significantly outperforms the best known STTC on both slow and fast fading channels.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"92 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":"115607569","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}
Joint iterative decoding of forward error control (FEC) encoded code-division multiple-access (CDMA) systems is studied. Serially concatenated convolutional codes are used as FEC codes. We apply iterative decoding to this system and study the effect of component decoders and different decoding partition schemes via a variance transfer analysis. It is shown that distinct partition schemes result in similar pinch off SNRs.
{"title":"Joint decoding of serially concatenated coded CDMA: iterative schedule study","authors":"Zhenning Shi, C. Schlegel","doi":"10.1109/ITW.2001.955135","DOIUrl":"https://doi.org/10.1109/ITW.2001.955135","url":null,"abstract":"Joint iterative decoding of forward error control (FEC) encoded code-division multiple-access (CDMA) systems is studied. Serially concatenated convolutional codes are used as FEC codes. We apply iterative decoding to this system and study the effect of component decoders and different decoding partition schemes via a variance transfer analysis. It is shown that distinct partition schemes result in similar pinch off SNRs.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"15 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":"127230855","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 give the asymptotic signal-to-interference ratio for the so-called widely linear minimum mean-squared error multiuser receiver for transmission of multiple users to a common receiver with DS-CDMA. Observing that widely linear multiuser detection virtually doubles the spreading factor, we show that transmission with real-valued channel symbols can lead to a higher spectral efficiency than with complex-valued channel symbols when each user employs its own complex-valued random spreading sequence.
{"title":"Asymptotic analysis of widely linear MMSE multiuser detection-complex vs real modulation","authors":"A. Lampe, M. Breiling","doi":"10.1109/ITW.2001.955134","DOIUrl":"https://doi.org/10.1109/ITW.2001.955134","url":null,"abstract":"We give the asymptotic signal-to-interference ratio for the so-called widely linear minimum mean-squared error multiuser receiver for transmission of multiple users to a common receiver with DS-CDMA. Observing that widely linear multiuser detection virtually doubles the spreading factor, we show that transmission with real-valued channel symbols can lead to a higher spectral efficiency than with complex-valued channel symbols when each user employs its own complex-valued random spreading sequence.","PeriodicalId":288814,"journal":{"name":"Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494)","volume":"5 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":"122393152","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}
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