Research On Space-Time Codes For MIMO Wireless Communication Systems

With the development of the mobile communication technology, multiple-input multiple-output (MIMO) system has become the hotspot. The technology figures prominently on the list of recent technical advandes with a chance of resolving the bottleneck of traffic capacity .A core idea in MIMO systems is space-time signal processing.Space-time codes can be divided into tree mainly parts: Bell Layered Space-Time Architecture(BLAST), Space-Time Trellis Codes(STTC) and Space-Time Block Codes(STBC).In this paper,we mainly compare the performance of BLAST and STBC in many aspects,such as design criterion,transmission rate,diversity gain,diversity combining,bit error rate and channel capacity etc.In this paper, we first respectively analysed the instantaneous received symbol energy-to-noise ratio of V_BLAST in the diversity combining methods of Maximal Ratio Combining(MRC),Equal Gain Combing(EGC) and Selective Combing(SC). Under Rayleigh fading channel ,we also simulated and compared BER in SISO,SIMO and MIMO systems.Secondly,based on careful study the BER and the channel capacity under white noise channel under MPSK modulation when the channel is Rayleigh fading,we duduced the expressions of STBC's BER and channel capacity under Rice and Nakagami fading.And also analysed the performances through numerical simulation using Matlab to testify the exactitude of the dudeced expressions.Finally,there exists an error floor of STBC through studying on its performance on time-selectiv fading channel.We analysed the reason and proposed two new decode combination scheme to eliminated the error floor and the performance of STBC on time-selective fading channel is improved.And also compared the two scheme's complication and SNR gain.