Results 1  10
of
13
Iterative Multiuser Joint Decoding: Optimal Power Allocation and LowComplexity Implementation
, 2002
"... We consider a canonical model for coded CDMA with random spreading, where the receiver makes use of iterative BeliefPropagation (BP) joint decoding. We provide simple DensityEvolution analysis in the largesystem limit (large number of users) of the performance of the exact BP decoder and of so ..."
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Cited by 63 (10 self)
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We consider a canonical model for coded CDMA with random spreading, where the receiver makes use of iterative BeliefPropagation (BP) joint decoding. We provide simple DensityEvolution analysis in the largesystem limit (large number of users) of the performance of the exact BP decoder and of some suboptimal approximations based on Interference Cancellation (IC). Based on this analysis, we optimize the received user SNR distribution in order to maximize the system spectral efficiency for given user channel codes, channel load (users per chip) and target user biterror rate. The optimization of the received SNR distribution is obtained by solving a simple linear program and can be easily incorporated into practical power control algorithms. Remarkably, under the optimized SNR assignment the suboptimal Minimum MeanSquare Error (MMSE) ICbased decoder performs almost as well as the more complex exact BP decoder. Moreover, for a large class of commonly used convolutional codes we observe that the optimized SNR distribution consists of a finite number of discrete SNR levels. Based on this observation, we provide a lowcomplexity approximation of the MMSEIC decoder that suffers from very small performance degradation while attaining considerable savings in complexity. As
List Detection for MultiAccess Channels
 in Proc. IEEE GLOBECOM ’02
, 2002
"... We propose a low complexity iterative multiuser decoder. We perform the multiuser aposteriori probability calculation based on the marginalization of probabilities over a subset of the P highest probable sequences. ..."
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Cited by 11 (2 self)
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We propose a low complexity iterative multiuser decoder. We perform the multiuser aposteriori probability calculation based on the marginalization of probabilities over a subset of the P highest probable sequences.
An Extrinsic Kalman Filter for Iterative Multiuser Decoding
"... One powerful approach for multiuser decoding is to iterate between a linear multiuser filter (which ignores coding constraints) and individual decoders (which ignore multipleaccess interference). Subject to clearly formulated statistical assumptions and the history of input signals provided by th ..."
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Cited by 11 (9 self)
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One powerful approach for multiuser decoding is to iterate between a linear multiuser filter (which ignores coding constraints) and individual decoders (which ignore multipleaccess interference). Subject to clearly formulated statistical assumptions and the history of input signals provided by the outer decoders over all previous iterations, an extrinsic Kalman filter is suggested. This approach is motivated by the recent observation that decoder outputs are loosely correlated during initial iterations. Numerical results show that iterative decoding using this filter provides better performance in terms of the supportable load and convergence speed as compared to previously suggested linearfilterbased iterative decoders.
Asymptotically optimal nonlinear MMSE multiuser detection based on multivariate Gaussian approximation
 IEEE Trans. Commun
, 2006
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Efficient Soft Demodulation of MIMO QPSK via Semidefinite Relaxation
, 2008
"... We develop a computationally efficient and memory efficient approach to (near) maximum a posteriori probability demodulation for MIMO systems with QPSK signalling, based on semidefinite relaxation. Existing approaches to this problem require either storage of a large list of candidate bitvectors, o ..."
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Cited by 7 (1 self)
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We develop a computationally efficient and memory efficient approach to (near) maximum a posteriori probability demodulation for MIMO systems with QPSK signalling, based on semidefinite relaxation. Existing approaches to this problem require either storage of a large list of candidate bitvectors, or the solution of multiple binary quadratic problems. In contrast, the proposed demodulator does not require the storage of a candidate list, and involves the solution of a single (efficiently solvable) semidefinite program per channel use. Our simulation results show that the resulting computational and memory efficiencies are obtained without incurring a significant degradation in performance.
Nonlinear MMSE multiuser detection based on multivariate Gaussian approximation
 IEEE Trans. on Commun
, 2005
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Iterative Multiuser Decoding with Maximal Ratio Combining
, 2004
"... In this paper we apply the concept of recursive maximal ratio combining over iterations in an iterative multiuser decoder. The principle can be applied to any multiuser estimator that does not exploit information across iterations. Here, we have applied the concept to a previously suggested iterativ ..."
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Cited by 4 (3 self)
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In this paper we apply the concept of recursive maximal ratio combining over iterations in an iterative multiuser decoder. The principle can be applied to any multiuser estimator that does not exploit information across iterations. Here, we have applied the concept to a previously suggested iterative linear minimum mean squared error filter, improving the load in terms of number of supported users at singleuserperformance by 20%, making this structure a strong linear alternative.
Application of maximal ratio combining for iterative multiuser decoding
 in IEEE Int. Symp. Inform. Theory
, 2004
"... Abstract — In this paper we apply the concept of recursive maximal ratio combining over iterations in an iterative multiuser decoder. The principle can be applied to any multiuser estimator that does not exploit information across iterations. I. SUMMARY Consider a synchronous Kuser CDMA system with ..."
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Cited by 4 (1 self)
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Abstract — In this paper we apply the concept of recursive maximal ratio combining over iterations in an iterative multiuser decoder. The principle can be applied to any multiuser estimator that does not exploit information across iterations. I. SUMMARY Consider a synchronous Kuser CDMA system with equalpower reception over an AWGN channel. User k encodes its binary information sequence {bk} using a rate R code C, to produce the coded binary sequence {dk}. Each user independently permutes and BPSKmodulates their encoded sequences resulting in the sequences {xk}. Each user transmits skxk, where sk ∈{−1, 1} N and xk ∈{−1, 1}. The chipmatched filtered received vector is r = Sx + n ∈ R N where n is circularly symmetric complex Gaussian with covariance E [ nn t] = σ 2 I. The basic principle behind iterative decoding is to decode independently
Multiuser detection based on Gaussian approximation
 IN PROC. WORKSHOP ON TELECOMM. INTERNET AND SIGNAL PROC
, 2004
"... In this paper, a class of nonlinear MMSE multiuser detectors are derived based on a multivariate Gaussian approximation of the multiple access interference. This approach leads to identical expressions as describing the probabilistic data association (PDA) detector, thus providing an alternative an ..."
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Cited by 1 (0 self)
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In this paper, a class of nonlinear MMSE multiuser detectors are derived based on a multivariate Gaussian approximation of the multiple access interference. This approach leads to identical expressions as describing the probabilistic data association (PDA) detector, thus providing an alternative analytical justification for this structure. A simplification to the PDA detector based on approximating the covariance matrix of the multivariate Gaussian distribution is suggested, resulting in a soft interference cancellation scheme. Corresponding multiuser softinput, softoutput detectors delivering extrinsic loglikelihood ratios are derived for application in iterative multiuser decoders. Numerical results demonstrate that for large systems, the bit error rate is accurately predicted by the analysis and found to be close to optimal performance.
Recursive Bayesian Filtering for Iterative Multiuser Decoding
 INT. SYMP. TURBO CODES
, 2003
"... One powerful approach for multiuser decoding is to iterate between a linear multiuser filter (which ignores coding constraints) and individual decoders (which ignore multipleaccess interference). Subject to clearly formulated statistical assumptions, a new recursive filter is derived based on the r ..."
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One powerful approach for multiuser decoding is to iterate between a linear multiuser filter (which ignores coding constraints) and individual decoders (which ignore multipleaccess interference). Subject to clearly formulated statistical assumptions, a new recursive filter is derived based on the received signal and all the successive estimates provided by the outer decoders over all previous iterations. This approach is motivated by the recent observation that these estimates are loosely correlated during initial iterations. Numerical results show that iterative decoding using this filter provides better performance in terms of the supportable load and convergence speed as compared to previously suggested linear filter based iterative decoders.