328 research outputs found
Optimum Asymptotic Multiuser Efficiency of Pseudo-Orthogonal Randomly Spread CDMA
A -user pseudo-orthogonal (PO) randomly spread CDMA system, equivalent to
transmission over a subset of single-user Gaussian channels, is
introduced. The high signal-to-noise ratio performance of the PO-CDMA is
analyzed by rigorously deriving its asymptotic multiuser efficiency (AME) in
the large system limit. Interestingly, the -optimized PO-CDMA transceiver
scheme yields an AME which is practically equal to 1 for system loads smaller
than 0.1 and lower bounded by 1/4 for increasing loads. As opposed to the
vanishing efficiency of linear multiuser detectors, the derived efficiency is
comparable to the ultimate CDMA efficiency achieved for the intractable optimal
multiuser detector.Comment: WIC 27th Symposium on Information Theory in the Benelux, 200
Gaussian Belief Propagation Based Multiuser Detection
In this work, we present a novel construction for solving the linear
multiuser detection problem using the Gaussian Belief Propagation algorithm.
Our algorithm yields an efficient, iterative and distributed implementation of
the MMSE detector. We compare our algorithm's performance to a recent result
and show an improved memory consumption, reduced computation steps and a
reduction in the number of sent messages. We prove that recent work by
Montanari et al. is an instance of our general algorithm, providing new
convergence results for both algorithms.Comment: 6 pages, 1 figures, appeared in the 2008 IEEE International Symposium
on Information Theory, Toronto, July 200
Generalised MBER-based vector precoding design for multiuser transmission
We propose a generalized vector precoding (VP) design based on the minimum bit error rate (MBER) criterion for multiuser transmission in the downlink of a multiuser system, where the base station (BS) equipped with multiple transmitting antennas communicates with single-receiving-antenna mobile station (MS) receivers each having a modulo device. Given the knowledge of the channel state information and the current information symbol vector to be transmitted, our scheme directly generates the effective symbol vector based on the MBER criterion using the particle swarm optimization (PSO) algorithm. The proposed PSO-aided generalized MBER VP scheme is shown to outperform the powerful minimum mean-square-error (MMSE) VP and improved MMSE-VP benchmarks, particularly for rank-deficient systems, where the number of BS transmitting antennas is lower than the number of MSs supported
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