The Experts below are selected from a list of 18114 Experts worldwide ranked by ideXlab platform
Helmut Bölcskei - One of the best experts on this subject based on the ideXlab platform.
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Optimal Diversity-Multiplexing Tradeoff in Selective-Fading MIMO Channels
arXiv: Information Theory, 2009Co-Authors: Pedro Coronel, Helmut BölcskeiAbstract:We establish the optimal diversity-multiplexing (DM) tradeoff of coherent time, frequency, and time-frequency Selective-Fading multiple-input multiple-output (MIMO) channels and provide a code design criterion for DM tradeoff optimality. Our results are based on the new concept of the "Jensen channel" associated to a given Selective-Fading MIMO channel. While the original problem seems analytically intractable due to the mutual information between channel input and output being a sum of correlated random variables, the Jensen channel is equivalent to the original channel in the sense of the DM tradeoff and lends itself nicely to analytical treatment. We formulate a systematic procedure for designing DM tradeoff optimal codes for general Selective-Fading MIMO channels by demonstrating that the design problem can be separated into two simpler and independent problems: the design of an inner code, or precoder, adapted to the channel statistics (i.e., the selectivity characteristics) and an outer code independent of the channel statistics. Our results are supported by appealing geometric intuition, first pointed out for the flat-Fading case by Zheng and Tse, IEEE Trans. Inf. Theory, 2003.
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Diversity-Multiplexing Tradeoff in Selective-Fading MIMO Channels
arXiv: Information Theory, 2007Co-Authors: Pedro Coronel, Helmut BölcskeiAbstract:We establish the optimal diversity-multiplexing (DM) tradeoff of coherent time, frequency and time-frequency Selective-Fading MIMO channels and provide a code design criterion for DM-tradeoff optimality. Our results are based on the analysis of the "Jensen channel" associated to a given Selective-Fading MIMO channel. While the original problem seems analytically intractable due to the mutual information being a sum of correlated random variables, the Jensen channel is equivalent to the original channel in the sense of the DM-tradeoff and lends itself nicely to analytical treatment. Finally, as a consequence of our results, we find that the classical rank criterion for space-time code design (in Selective-Fading MIMO channels) ensures optimality in the sense of the DM-tradeoff.
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ISIT - Diversity-Multiplexing Tradeoff in Selective-Fading MIMO Channels
2007 IEEE International Symposium on Information Theory, 2007Co-Authors: Pedro Coronel, Helmut BölcskeiAbstract:We establish the optimal diversity-multiplexing (DM) tradeoff of coherent time, frequency and time-frequency Selective-Fading MIMO channels and provide a code design criterion for DM-tradeoff optimality. Our results are based on the analysis of the "Jensen channel" associated to a given Selective-Fading MIMO channel. While the original problem seems analytically intractable due to the mutual information being a sum of correlated random variables, the Jensen channel is equivalent to the original channel in the sense of the DM-tradeoff and lends itself nicely to analytical treatment. Finally, as a consequence of our results, we find that the classical rank criterion for space-time code design (in Selective-Fading MIMO channels) ensures optimality in the sense of the DM-tradeoff.
Tolga M. Duman - One of the best experts on this subject based on the ideXlab platform.
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Belief Propagation over SISO/MIMO Frequency Selective Fading Channels
IEEE Transactions on Wireless Communications, 2007Co-Authors: Kaynak Mustafa N, Tolga M. Duman, Erozan M. KurtasAbstract:In this letter, we propose an iterative belief propagation (BP) channel detector (equalizer) over single-input single- output (SISO) and multiple-input multiple-output (MIMO) frequency Selective Fading channels as an alternative to the typically used maximum a-posteriori (MAP) or maximum likelihood (ML) detectors. The proposed detector has a parallel structure, resulting in fast hardware implementations. Moreover, BP detector is less complex than the MAP detector and it has a short decoding delay. We analyze the bit error rate and the mutual information and show that, over frequency Selective Fading channels, the proposed BP detector achieves a near-optimal performance, even in the presence of the length 4 cycles in the corresponding channel factor graph.
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ICAS/ICNS - Belief Propagation over MIMO Frequency Selective Fading Channels
Joint International Conference on Autonomic and Autonomous Systems and International Conference on Networking and Services - (icas-isns'05), 2005Co-Authors: Kaynak Mustafa N, Tolga M. Duman, Erozan M. KurtasAbstract:In this paper, we propose an iterative belief propagation (BP) detector over multiple-input multiple-output (MIMO) frequency Selective Fading channels as an alternative to the typically used maximum a-posteriori (MAP) or Viterbi detectors. Unlike the trellis based detectors having serial structure, the proposed detector has the advantage of having a parallel structure, resulting in more efficient and fast hardware implementations. Moreover, BP detector is less complicated than the MAP detector and it has a short decoding delay which is essential for reduced memory requirements. Via simulations we show that, over frequency Selective Fading channels, the proposed BP detector achieves a near-optimal performance, even in the presence of the length 4 cycles in the channel factor graph
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ICC - Soft input soft output stack equalization for MIMO frequency Selective Fading channels
IEEE International Conference on Communications 2005. ICC 2005. 2005, 1Co-Authors: Tansal Gucluoglu, Tolga M. DumanAbstract:In this paper, we propose a soft-input soft-output stack equalizer for multiple input multiple output (MIMO) frequency Selective Fading channels. In the literature, the soft or hard input/output stack algorithms to equalize single or multiple antenna time-invariant intersymbol interference (ISI) channels exist. After some modifications of the original sequential decoding metric, we show that the soft-input soft-output stack algorithm can be used at the receiver of the coded systems over frequency Selective Fading channels. Our examples illustrate that the proposed metrics result in promising near-optimum equalizers while offering a complexity independent of the memory of the channel.
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VTC Fall (2) - Belief propagation over frequency Selective Fading channels
IEEE 60th Vehicular Technology Conference 2004. VTC2004-Fall. 2004, 1Co-Authors: Kaynak Mustafa N, Tolga M. Duman, Erozan M. KurtasAbstract:In this paper, we propose an iterative belief propagation (BP) based equalizer for frequency Selective Fading channels as an alternative to the typically used maximum a-posteriori (MAP), Viterbi, or soft output Viterbi algorithm (SOVA) based equalizers. The proposed equalizer has a parallel structure unlike the trellis based equalizers and it is less complicated than the MAP equalizer. Via simulations we show that, over frequency Selective Fading channels, a BP based equalizer achieves the optimal maximum a-posteriori performance, even in the presence of the length 4 cycles. We also discuss the joint decoding of an outer error correcting code and the equalization of the frequency Selective Fading channel using a joint factor graph and a BP based equalizer.
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ICASSP (4) - Antenna selection for space time coding over frequency-Selective Fading channels
2004 IEEE International Conference on Acoustics Speech and Signal Processing, 1Co-Authors: Tansal Gucluoglu, Tolga M. Duman, Ali GhrayebAbstract:We deal with antenna selection at the receiver side for space-time coded systems over frequency-Selective Fading channels. We reveal that introducing antenna selection based on the signal-to-noise-ratio (SNR) observed can still achieve the full diversity available, if the underlying space-time code (STC) is full-rank (i.e., if it achieves full diversity without antenna selection over the frequency-Selective Fading channel). We also argue that if the code is not full-rank, antenna selection results in a loss in the diversity of the system.
Heung Ki Baik - One of the best experts on this subject based on the ideXlab platform.
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PIMRC - Decision feedback detection for space-time block coding over time-Selective Fading channels
14th IEEE Proceedings on Personal Indoor and Mobile Radio Communications 2003. PIMRC 2003., 1Co-Authors: Kyung Seung Ahn, Heung Ki BaikAbstract:Most existing space-time coding (STC) schemes have been developed for flat Fading channels. To obtain antenna diversity gain, they rely on channel state information (CSl) required at the receiver through channel estimation techniques. This paper proposes a new decision feedback decoding scheme for Alamouti-based space-time block coding (STBC) transmission over time-Selective Fading channels. In wireless channels, time-Selective Fading effects arise mainly due to Doppler shift and carrier frequency offset. Modelling the time-Selective Fading channels as the first-order Gauss-Markov processes, we use recursive algorithms such as Kalman filtering, LMS and RLS algorithms for channel tracking. The proposed scheme consists of the symbol decoding stage and channel tracking algorithms. Computer simulations confirm that the proposed scheme shows the better performance and robustness to time-selectivity.
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ICASSP (4) - Bit error rate performance of decision feedback detection for space-time block coded systems over time-Selective Fading channels
Proceedings. (ICASSP '05). IEEE International Conference on Acoustics Speech and Signal Processing 2005., 1Co-Authors: Kyung Seung Ahn, Jae-young Kim, Heung Ki BaikAbstract:In wireless channels, time-Selective Fading effects arise mainly due to Doppler shift and carrier frequency offset. In time-Selective Fading channels, the Alamouti-based decoding scheme has an error floor caused by interference due to time-selectivity. This paper proposes decision feedback detector for the Alamouti scheme to mitigate the effects of a time-Selective Fading channel. Moreover, we present an evaluation of the average bit error rate (BER) performance of the proposed scheme over time-Selective Fading channels.
Erozan M. Kurtas - One of the best experts on this subject based on the ideXlab platform.
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Belief Propagation over SISO/MIMO Frequency Selective Fading Channels
IEEE Transactions on Wireless Communications, 2007Co-Authors: Kaynak Mustafa N, Tolga M. Duman, Erozan M. KurtasAbstract:In this letter, we propose an iterative belief propagation (BP) channel detector (equalizer) over single-input single- output (SISO) and multiple-input multiple-output (MIMO) frequency Selective Fading channels as an alternative to the typically used maximum a-posteriori (MAP) or maximum likelihood (ML) detectors. The proposed detector has a parallel structure, resulting in fast hardware implementations. Moreover, BP detector is less complex than the MAP detector and it has a short decoding delay. We analyze the bit error rate and the mutual information and show that, over frequency Selective Fading channels, the proposed BP detector achieves a near-optimal performance, even in the presence of the length 4 cycles in the corresponding channel factor graph.
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ICAS/ICNS - Belief Propagation over MIMO Frequency Selective Fading Channels
Joint International Conference on Autonomic and Autonomous Systems and International Conference on Networking and Services - (icas-isns'05), 2005Co-Authors: Kaynak Mustafa N, Tolga M. Duman, Erozan M. KurtasAbstract:In this paper, we propose an iterative belief propagation (BP) detector over multiple-input multiple-output (MIMO) frequency Selective Fading channels as an alternative to the typically used maximum a-posteriori (MAP) or Viterbi detectors. Unlike the trellis based detectors having serial structure, the proposed detector has the advantage of having a parallel structure, resulting in more efficient and fast hardware implementations. Moreover, BP detector is less complicated than the MAP detector and it has a short decoding delay which is essential for reduced memory requirements. Via simulations we show that, over frequency Selective Fading channels, the proposed BP detector achieves a near-optimal performance, even in the presence of the length 4 cycles in the channel factor graph
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VTC Fall (2) - Belief propagation over frequency Selective Fading channels
IEEE 60th Vehicular Technology Conference 2004. VTC2004-Fall. 2004, 1Co-Authors: Kaynak Mustafa N, Tolga M. Duman, Erozan M. KurtasAbstract:In this paper, we propose an iterative belief propagation (BP) based equalizer for frequency Selective Fading channels as an alternative to the typically used maximum a-posteriori (MAP), Viterbi, or soft output Viterbi algorithm (SOVA) based equalizers. The proposed equalizer has a parallel structure unlike the trellis based equalizers and it is less complicated than the MAP equalizer. Via simulations we show that, over frequency Selective Fading channels, a BP based equalizer achieves the optimal maximum a-posteriori performance, even in the presence of the length 4 cycles. We also discuss the joint decoding of an outer error correcting code and the equalization of the frequency Selective Fading channel using a joint factor graph and a BP based equalizer.
Huaping Liu - One of the best experts on this subject based on the ideXlab platform.
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MIMO-OFDM Systems in the Presence of Phase Noise and Doubly Selective Fading
IEEE Transactions on Vehicular Technology, 2007Co-Authors: Yu Zhang, Huaping LiuAbstract:In this paper, we analyze the effects of phase noise to multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems over doubly Selective Rayleigh Fading channels. Similar to single-antenna OFDM, MIMO-OFDM suffers from significant performance degradation due to phase noise and time-Selective Fading, which causes inter- carrier interference (ICI). We derive the expressions of carrier- to-interference and signal-to-interference-plus-noise ratios. After characterizing the common phase error (CPE) caused by phase noise and ICI caused by phase noise, as well as time-Selective Fading, we then derive a minimum mean-squared error-based scheme to mitigate the effect of both phase noise and time-Selective Fading. We also evaluate and compare the performances of various detection schemes combined with the proposed CPE mitigation scheme. Through numerical results, we examine the relative performances and the potential error floors of these detection schemes.
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Impact of time-Selective Fading on the performance of quasi-orthogonal space-time-coded OFDM systems
IEEE Transactions on Communications, 2006Co-Authors: Yu Zhang, Huaping LiuAbstract:In this paper, we study the impact of time-Selective Fading on quasi-orthogonal space-time (ST) coded orthogonal frequency-division multiplexing (OFDM) systems over frequency-Selective Rayleigh Fading channels. OFDM is robust against frequency-Selective Fading, but it is more vulnerable to time-Selective Fading than single-carrier systems. In ST-OFDM, channel time variations cause not only intercarrier interference among different subcarriers in one OFDM symbol, but also intertransmit-antenna interference. We quantify the impact of time-Selective Fading on the performance of quasi-orthogonal ST-OFDM systems by deriving, via an analytical approach, the expressions of carrier-to-interference and signal-to-interference-plus-noise ratios. We observe that system error performance is insensitive to changes in vehicle speeds and the channel power-delay profile, but very sensitive to changes in the number of subcarriers. We also evaluate the performance of five different detection schemes in the presence of time-Selective Fading. We show that although there exist differences in their relative performances, all these detection schemes suffer from an irreducible error floor.
