Approximately 3 dB signal-to-noise ratio (SNR) loss is always paid with conventional differential space-time block codes (STBCs), compared with coherent STBCs. In this paper, a multiple-symbol differential detection (MSDD) technique is proposed for M-ary phase-shift keying (PSK) STBCs. The new scheme can greatly narrow the 3-dB performance gap by extending the observation interval for differential decoding. The technique uses maximum-likelihood sequence detection instead of traditional symbol-by-symbol detection, and is carried out on the slow, flat Rayleigh fading channel. A generalized decision metric is derived for an observation interval of arbitrary length. It is shown that for a moderate number of symbols, MSDD provides approximately 1.5 dB performance improvement over conventional differential detection. In addition, a closed-form pairwise error probability and approximate bit-error probability (BEP) are derived for multiple-symbol differential binary PSK STBC. Results show that the theoretical BEP matches simulation results well. The BEP is shown to converge asymptotically with the number of symbols in the observation interval to that of the differential scheme with coherent detection.

A differential detection scheme for a multiple-input multiple-output (MIMO) DS/CDMA link is presented, where neither the transmitters nor the receivers know the channel state information (CSI). The transmission provides for full spatial diversity gain by a simple detection scheme, which is the natural extension of differential detection combined with an orthogonal transmit diversity (OTD) approach. Moreover, a capacity analysis for this scheme is illustrated. The capacity analysis and simulation results show that 3 dB loss is paid for differential detection compared to coherent detection.