Research On Linear Space Time Code With Its Applications

With the development of wireless mobile communications, the customer demand for services has changed from speech only to multimedia, which requires the communication system can provide high capacity and reliability. The multi-path and time-varying nature of the wireless channel has negative effect on the transmitted signals, and the scarcity of frequency resource limits the capacity of communication system. The space-time code has a high advantage to solve this problem. It can realize wireless transmission with high spectrum efficiency, and have a strong capability to cope with the multi-path fading. It can provide the system with high reliability and capacity.In this dissertation, our research focuses on the technologies of MIMO, space-time code and OFDM.First, we present a new concept, linear space time code, which includes orthogonal space time block code(STBC), layered space time code(LST) and linear dispersion code(LDC). The proposed concept unifies the three kinds of codes with different design purpose. STBC and LST code are mainly designed for achieving diversity or multiplexing gain, LDC is the tradeoff of them. Then, we study the coding and decoding methods of the linear space time code and give the error probability curve of the three codes by computer simulation.Secondly, we analyze the diversity and multiplexing performance of the linear space time code from a novel point of view: the tradeoff between diversity gain and multiplexing gain. We draw a conclusion that the orthogonal STBC can obtain all of the diversity gain of the MIMO system, the LST code can obtain all of the multiplexing gain of the MIMO system, and the LDC is the tradeoff between STBC and LST code.