The University of Southampton
University of Southampton Institutional Repository

Iterative Near-Maximum-Likelihood Detection in Rank-Deficient Downlink SDMA Systems

Wei, C.Y., Akhtman, J., Ng, S.X. and Hanzo, L. (2008) Iterative Near-Maximum-Likelihood Detection in Rank-Deficient Downlink SDMA Systems IEEE Transactions on Vehicular Technology, 57, (1), pp. 653-657.

Record type: Article


Abstract—In this paper, a precoded and iteratively detected downlink multiuser system is proposed, which is capable of operating in rankdeficient scenarios, when the number of transmitters exceeds the number of receivers. The literature of uplink space division multiple access (SDMA) systems is rich, but at the time of writing there is a paucity of information on the employment of SDMA techniques in the downlink. Hence, we propose a novel precoded downlink SDMA (DL-SDMA) multiuser communication system, which invokes a low-complexity nearmaximum-likelihood sphere decoder and is particularly suitable for the aforementioned rank-deficient scenario. Powerful iterative decoding is carried out by exchanging extrinsic information between the precoder’s decoder and the outer channel decoder. Furthermore, we demonstrate with the aid of extrinsic information transfer charts that our proposed precoded DL-SDMA system has a better convergence behavior than its nonprecoded DL-SDMA counterpart. Quantitatively, the proposed system having a normalized system load of Ls = 1.333, i.e., 1.333 times higher effective throughput facilitated by having 1.333 times more DL-SDMA transmitters than receivers, exhibits a “turbo cliff” at an Eb/N0 of 5 dB and hence results in an infinitesimally low bit error rate (BER). By contrast, at Eb/N0 = 5 dB, the equivalent system dispensing with precoding exhibits a BER in excess of 10%. Index Terms—Iterative decoding, maximum likelihood detection, space division multiple access (SDMA) downlink, sphere decoding.

PDF 04358461.pdf - Other
Download (192kB)

More information

Published date: January 2008
Organisations: Southampton Wireless Group


Local EPrints ID: 265119
ISSN: 0018-9545
PURE UUID: 35688b40-2a89-44d2-a0dd-245a541a0568

Catalogue record

Date deposited: 27 Jan 2008 17:24
Last modified: 18 Jul 2017 07:29

Export record


Author: C.Y. Wei
Author: J. Akhtman
Author: S.X. Ng
Author: L. Hanzo

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton:

ePrints Soton supports OAI 2.0 with a base URL of

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.