Simulation Researches On The Space-Time Coding And Decoding Technology Of MIMO-OFDM System

Since current wireless communication systems can not satisfy the increasing requirement of services, the third and beyond-third generation (3G/B3G) of mobile communication standards emerges, aiming at achieving higher data transmit rate in the limited bandwidth. The recent research results show that the multiple-input multiple-output (MIMO) technology can increase the system capacity significantly. As one of the key signal processing technologies of MIMO, the space time code (STC) can provide diversity and coding gain from the joint coding both in space and time domain without any increase of bandwidth. Proposed in 1990s, the STC has been widely studied and made many important progresses.Firstly, the introduction to the research background of the researches and the overviews of the current space-time coding studies and applications are provided in the thesis.Secondly, the MIMO channel modeling and simulation are investigated, based on which, an improved MIMO channel simulation model is proposed. Both spatial correlation and fading in time domain are integrated into this model. Various channel parameters such as time dispersion, Doppler effect, angle of arrival and azimuth spread are fully considered in the proposed model. Simulation results provided verify the correctness of the model.Thirdly, three representative space-time codes, layered space-time code (LTC), space-time block codes (STBC) and space-time trellis code (STTC), are analyzed and the detailed analysis of the encoding and decoding principles is presented. In the context of MIMO channel model, LSTC, STBC and STTC system are simulated and analyzed.Finally, the combined space-time code and orthogonal frequency division multiplexing (OFDM) is investigated. The basic principles of OFDM are introduced in detail, on the basis of which, the MIMO-OFDM system model is presented so as to pave the way for the establishment of simulation model. Further, simulation results of STC-OFDM and OFDM system performance in frequency selective fading channel are presented, which show that the STC-OFDM exhibits better performance than OFDM due to the factor that space-time coding can achieve diversity gain from both space-time diversity and frequency diversity.