The Research Of Space-Time Coding Technic In MIMO System

Space-time codes based on MIMO is almost the unique solution for future bandwidth- limited high-speed wireless communication systems. This novel transmit diversity technique, which combines channel coding, modulation and signal processing at receive terminal, can make full use of the fading multi-path in the wireless communication systems so as to mitigate the signal attenuation.This technique is mainly designed to combat channel fading in downlink transmission by combining the technique of channel coding and that of array diversity, hence increasing the capacity of wireless communications systems and giving diversity gain and coding gain to them.This dissertation investigates several issues related to this hot research topic. In this thesis, we briefly introduce the development of STC, and study the characteristic and the simulations models of two kinds of fading channel. The combination of space-time coding technique and orthogonal frequency division multiplexing (OFDM) technique (STC-OFDM) is investigated. Based on this, an OFDM system with concatenated Tcm coding and stbc is proposed. The performance analysis and computer simulation results of the system over the wireless. Rayleigh fading channel show that the system can explore all the diversity resources and performance of STC-OFDM can be improved a lot. Simulation results show that the proposed achieve much better performance than the traditional STC-OFDM.Researches on the space - time code have been under the assumption of independent fading and perfect channel state information. But in a realistic system , the above assumption is very difficult to be acquired. Based on this , the performance of space - time code under correlated Rayleigh fading channel and Rician fading channel is studied in thispaper.The assumption that the channel is known is questionable in a rapidly changing mobile environment, or when multiple transmitter antennas are employed. Unitary space-time codes and differential unitary space-time codes don't need any channel information. We discuss the unitary space-time codes briefly and study the details of the DUSTC, including the fundamental differential transmission and receiver equation, and parameters searching algorithm.The parameters searching and simulations results is proposed. Then we analyze the exact PEP and union bound of SEP of the DUSTC. And the conclusion that different range of SNRs needs different searching criteria is proposed. Finally, we search these parameters in the group constellation based on union bound criteria, and simulate thperformance in the Rayleigh fading channel.