The Study Of Quasi-Orthogonal Space-Time Block Code In Mimo System

With the development of mobile communication, the future wireless communication systems require higher transmission rate and communication reliability. It is required that the future wireless communication system must be high spectrum efficiency system because the frequency resource of communication system is limited.MIMO (multiple-input multiple-output) communication system can provide tremendous capacity. Space-time coding (STC) based on MIMO systems combines the technique of channel coding with antenna diversity, and it can improve the diversity gain and coding gain remarkably and eliminate the interference and contradict the multi-path fading effectively, thereby the capacity of wireless communication system is increased greatly. So this technique provides a new solution to the problem of limited bandwidth in wireless communication. Space-time coding includes layered space-time coding (LSTC), space-time trellis coding (STTC) and space-time block coding (STBC). As STBC is a kind of STC with simple structure, and its easy implement and its good compatibility. This thesis focuses on STBC,the main contents are as follows:Firstly, the quasi-orthogonal space-time block code encoding and decoding algorithms is studied in depth, and an improved U. Park code is proposed based on U. Park code. This scheme uses two simple rotation matrixes to eliminate self-interference terms brought by non-orthogonal in rotational Quasi- orthogonal space-time block codes (QO-STBC). Compared with rotational QO-STBC code we can reduce the decoding complexity. The decoding complexity is not increased compared with the U. Park code. And also analyses the performance through numerical simulation using Matlab, simulation results demonstrate that the BER performance significantly improved compared with the U. Park code.Secondly, we analyzed the exist problem in a high-rate full diversity space-time block code and proposed an improved high-rate full diversity space-time block code. This scheme uses twin QPSK modulation to solve the problem which can only applies BPSK modulation. We carried out simulations of two methods, simulation results demonstrate that the superiority of the BER performance.