The Research On Random Channel And Orthogonal Space-Time Coding In MIMO System

The third generation wireless communication systems require higher communication quality and transmission rate than cellular wireless standard, and the traditional communication systems using single-antenna transmitting and receiving are confronted with a stiff challenge to achieve this target. MIMO methods make use of the radio link, which has provided a novel solution to this problem. The technique of space-time coding(STC) is mainly designed by combining the technique of channel coding and array diversity, hence increasing the capacity of wireless communication systems and improving communication quality of multipath fading channel.The dissertation has mainly made further research on the related theories about four main aspects: the characteristics of random channel in MIMO system, channel capacity, orthogonal space-time coding and improved coding method base on recent work and a few new conclusions were derived in the dissertation. Moreover, the important results were obtained by a number of computer simulations. The main contents of the dissertation are expressed as follows:(1) The charaderistics of wireless channel and trasmitting environment are studied in depth. On the basis of recent research on the theories of space-time model, a random channel model in 3G and multi-antenna MIMO system was built. According to correlation function of channel fading coefficient, the angle of departure of transmitting signal and its spread angle, power horizontal distribution and Doppler spectrum, the simulation method and simulation analysis of the random channel model are given.(2) It is specifically analyzed the capacity for rapid Raleigh fading channel, block Raleigh fading channel and slow Raleigh fading channel with random channel coefficient. The simulation results in MIMO system are also given.(3) Orthogonal Space-time Block Coding(OSTBC) is a key technology in MIMO communications. It has simply encode and decode algorithm and the most diversity. It is specifically studied Orthogonal Space-time Coding principle, theorthogonal design of Space-time Block Coding , encode&decode process of Orthogonal Space-time Block Coding and the related simulation results are given.(4) It is proposed an improved space-time coding based on orthogonal design. For the joint diversity and multiplexing performance, on the basis of the research on OSTBC, it is proposed Orthogonal Llinear Dispersion Space-time Code(OLDC) based on Linear Dispersion Space-time Code(LDC). Simulation results show that OLDC performance better than traditional LDC on BER, diversity and multiplexing capacity.