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  • Research Article
  • Open Access

Super-Orthogonal Space-Time Turbo Transmit Diversity for CDMA

  • 1Email author,
  • 2 and
  • 3
EURASIP Journal on Advances in Signal Processing20052005:485853

  • Received: 8 September 2003
  • Published:


Studies have shown that transmit and receive diversity employing a combination of multiple transmit-receive antennas (given ideal channel state information (CSI) and independent fading between antenna pairs) will potentially yield maximum achievable system capacity. In this paper, the concept of a layered super-orthogonal turbo transmit diversity (SOTTD) for downlink direct-sequence code-division multiple-access (CDMA) systems is explored. This open-loop transmit diversity technique improves the downlink performance by using a small number of antenna elements at the base station and a single antenna at the handset. In the proposed technique, low-rate super-orthogonal code-spread CDMA is married with code-division transmit diversity (CDTD). At the mobile receiver, space-time (ST) RAKE CDTD processing is combined with iterative turbo code-spread decoding to yield large ST gains. The performance of the SOTTD system is compared with single- and multiantenna turbo-coded (TC) CDTD systems evaluated over a frequency-selective Rayleigh fading channel. The evaluation is done both by means of analysis and computer simulations. The performance results illustrate the superior performance of SOTTD compared to TC CDTD systems over practically the complete useful capacity range of CDMA. It is shown that the performance degradation characteristic of TC CDTD at low system loads (due to the inherent TC error floor) is alleviated by the SOTTD system.

Keywords and phrases

  • transmitter diversity
  • space-time coding
  • code-division transmit diversity
  • layered super-orthogonal turbo transmit diversity
  • low-rate spreading and coding
  • CDMA wireless communications

Authors’ Affiliations

RapidMobile (Pty)Ltd, Persequor Park, Pretoria, 0020, South Africa
Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria, 0002, South Africa
Broadcom, 15435 Innovation Drive, San Diego, CA 92128, USA


© Daniël J. van Wyk et al. 2005

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.