Research On The Capacity For MIMO System

Multiple antenna wireless systems have attracted increasingly significant attention due to their high capacity and good immunity to the channel fading. In the past, most researches on MIMO have made the assumption that channel between antenna pairs is independent. However, in the actual wireless transmission enviroment, correlation usually exists in MIMO channel due to the restriction of the receiver or poorly scattering environment. In this thesis, the effect of spatial correlation on MIMO systems reachered, specifically, on the capacity of MIMO and the performance of space-time block codes. As an effective way to reduce the impact of spatial correlation on MIMO systems' capacity, antenna selection is another part in this thesis.Firstly, some average capacities of several typical systems, such as SISO, MISO, SIMO, MIMO, are theoretically analyzed and simulated from the point of view of information theory. The difference among those typical systems is compared and the relationship between the capacity and different schemes of distributing power are discussed. Secondly, the effects of spatial correlation on the capacity of MIMO systems and the performance of space-time block codes are mainly reseacher. Theoretical analysis and the results of simulation indicate that the influence on channel capacity and the performance of BER from spatial correlation is same, therefore, correlative coefficient is the littler and the effect of their performance is the littler, vice versa. And system will become more sensitive for the spatial correlation with the increasing numbers of system antennas. Lastly, the influence on channel capacity of the deficient order from antenna selection is mainly studied, and kinds of simulations are made according to different parameters. The results of simulations show that the loss of capacity from spatial correlation can be reduced and channel capacity can be increased by antenna selection of transmitting side. In the receiving port, selecting the antennas that can reduce the cost and complexity of the MIMO system, it only has the less loss of capacity. So it is very important to design the MIMO systems.