Adaptive Switching Between MIMO Diversity And Multiplexing In WiMAX System

WiMAX(Worldwide Interoperability Microwave Access)is a new generation of broadband wireless access system which based on IEEE802.16, it has been studied by lots of researchers for its tremendous advantages, such as high transmission rate, big coverage radius and against fading. WiMAX has been used in commercial and has a bright future. As a key technology of WiMAX system's physical layer, MIMO plays a crucial role to improve transmission rate and anti-fading capabilities, so it's a meaningful topic to research MIMO in WiMAX system.This thesis focus on the adaptive switching between MIMO diversity and multiplexing in WiMAX system. Diversity and multiplexing are two ways of MIMO applications, compared to diversity, the transmission rate of multiplexing is higher and the capacity is greater, but the multiplexing way lossed a part of diversity gain and Lead to decreased the reliability. Although the diversity way has a higher reliability and received SINR, but at the expense of system throughput and system capacity. Diversity and multiplexing are mutually contradictory, it is worth discussing deeply how to obtain the maximum system gain through using diversity and multiplexing reasonably.After introducing the development and the prospects of WiMAX and MIMO, some key technologies of WiMAX system, MIMO system's model and the capacity of MIMO system are presented in Chapter II. In Chapter III, The principles and applications of diversity and multiplexing are described in detail. Then, some typical algorithms of adaptive switching between MIMO diversity and multiplexing are analyzed. It is found that these algorithms considered only one side of reliability and throughput instead of considering both sides together. In the actual communication environment, one side of reliability and throughput is focus on under different circumstances. An adaptive switching algorithm of MIMO diversity and multiplexing based on the spectrum resources and channel conditions is proposed in this thesis, the algorithm considering reliability and throughput together under different circumstances. Through the comparison of the simulation results, we can come to the conclusion that the performance of the new daptive switching algorithm of MIMO diversity and multiplexing is much better than only use diversity or multiplexing.