CDMA: principles of spread spectrum communication
CDMA: principles of spread spectrum communication
Space-Time Processing for CDMA Mobile Communications
Space-Time Processing for CDMA Mobile Communications
IEEE Transactions on Information Theory
Performance evaluation of superorthogonal turbo codes in AWGN and flat Rayleigh fading channels
IEEE Journal on Selected Areas in Communications
A simple transmit diversity technique for wireless communications
IEEE Journal on Selected Areas in Communications
A space-time coding modem for high-data-rate wireless communications
IEEE Journal on Selected Areas in Communications
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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 bymeans 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.