Application Research Of Space Time Coding In MIMO-OFDM System

Future wideband wireless communications are supposed to provide data rate of over 100Mbps to satisfy audio and various multimedia services. To achieve this goal, there are two main challenges: providing high data rate wireless service with good performance and affordable technique complexity in frequency selective fading channels. As a combination of Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM), MIMO-OFDM technique takes the advantages of both MIMO and OFDM and serves as a promising scheme for the future broadband wireless communications. As one of the core components of MIMO techniques, space-time coding constitutes station of important transmission schemes based on multiple transmitters and receivers.This thesis does extensive studies on MIMO-OFDM systems and mainly focuses on its key techniques concerning coding techniques. We began our investigation by studying the channel model and capacity of MIMO. We continued our investigation with discussions of the three main space-time coding schemes, namely layered space-time coding (LSTC), space-time trellis coding (STTC) and space-time block coding (STBC). We analyzed the codes principles and the pros and cons of the three schemes. Then fundamentals of OFDM technology are introduced And after studying the factors that will affect the MIMO-OFDM systems, we built a simple simulation model that are four transmit and one or two receiver antennas to evaluate the performance of the MIMO-OFDM system.The Quasi-Orthogonal Space-Time Block Code (QOSTBC) was introduced in MIMO-OFDM system for solution the problem that the OSTBC can not reach full rate in antennas number more than 2 situation and the simulation result show the rate has two times improve in small loss of performance in this paper. Finally, the orthogonal precoding was introduced for further improve the performance. the Space-Time Frequency Code (STFC) has be obtained can get gain of code in frequency area and the result show it was a high rate scheme of codeing and the system performance has be improved.