Research On Space-Time Block Codes Under Selective Fading Channels

MIMO technique is one of the key techniques for 3G and the future generation mobile communications. As the one of the kernel parts of MIMO architecture, Space-Time Coding (STC) technique has been shown to be very effective at mitigating the effects of multipath fading as well as increasing the capacity in wireless systems by using joint design of transmit diversity and coding and modulation techques. Space-time coding has become increasingly popular research subject in mobile communications in recent years.Space-time block coding (STBC) has generated much interest in STC research and has been adopted in the 3GPP standard. Most of existing STBC are proposed for space-independent slow fading channels which are not the case in practical situations. Thus the investigation of appropriate STBC schemes for channels that are space-correlated and fast fading is of practical significance. Starting from the investigation of the fundamental theory of STBC, this paper is concentrated on the STBC decoder over time-varying channels and the performance analysis of STBC over space-correlated channels. The main contents and contributions of this paper are as follows:1.The STBC decoder schemes over time-varying channels are systematically summarized and the main problems of ML and Alamouti decoder used for the time-varying channels are indicated in this paper. On the basis of introduction alternate detection strategies — Decision-Feedbadk (DF) detector and Zero-Forcing(ZF) detector, STBC decoder using multi-received antennas over time-varying is been researched. DFMRC and ZFMRC based on MRC scheme and DAC-DF and DAC-RZF based on DAC scheme are proposed. Simulation results have shown the proposed decodeds are efficient.2. STBC-OFDM system is been examined and DAC-DF is proposed to be used in STBC-OFDM system to mitigate the effects of the intertransmit antennas interference (ITAI) over non-flat time-varying channels in this paper. The better BER performance is shown by simulation results.