Study On MIMO System Based On Space-Time Block Coding

Multi-path fading is the main factor that influences the quality of receiving signals in mobile communications. There are several anti-fading techniques. Diversity includes receiver diversity and transmitter diversity. Space-time block coding (STBC) is a new coding technique, which is combined with receiver diversity and transmitter diversity. Multiple antennas are used for both transmitter and receiver, so they are usually called multiple-input-multiple-output. STBC has better performance than common channel coding, because its signals simultaneously include spatial and temporal correlation. Also STBC has already been proposed to be a key technique by 3G standard, so the research on it is very necessary。The performance and characteristic of MIMO system based on STBC are introduced from theory study and DSP realization. In the term of theory study,Firstly,channel capacity of MIMO system based on STBC are studied, formula of capacity is deduced and comparison of capacity between STBC and other space-time coding are made. Secondly influence in system performance that is caused by the number and relativity of antenna is studied. The principle of coding and decoding, channel simulation model, system model are given, the effect of the relativity of antenna is simulated and method that reduces the influence is put forward. Finally, method of decoding is studied and a simple method for decoding is put forward. The method is expounded based on 8PSK, 16APSK, 16QAM and compared in the complexity with maximum likelihood decoding. In the part of DSP realization, system model is built and the system is simulated using MATLAB.Realization arithmetic of modules in transmitting and receiving part. Also the system is simulated in CCS and run on TMS320C5402 EVM board.The results of experiment show that channel capacity of STBC is lower than that of other space-time coding, but good diversity gain and simple decoding arithmetic are given. simple decoding arithmetic is an effect decoding method, which decrease decoding complexity without changing system performance. Also, channel capacity will be increased with number of antenna increasing, but because of the relativity of antennas, real capacity will lower than theory capacity. The method of antenna selection can deduce the effect of antenna relativity.