Wimax Systems Mimo Applications, A Number Of Key Technology Research

MIMO(Multiple Input and Multiple Output) technology is considered as the development trend of wireless communication technologies. It can get rid of the constraint of radio frequency resource, and greatly increase the spectral efficiency of wireless communication system. As a new generation of broadband wireless access system based on IEEE802.16, WiMAX (Worldwide Interoperability Microwave Access) has been studied by lots of researchers for its tremendous advantages, such as anti-fading, big coverage radius, and it is close to commercial deployment. A lot of problems need to be solved in the application of MIMO in WiMAX system.The following fields are discussed in this dissertation: the algorithm of adaptive switching between MIMO diversity and multiplexing; the influences of MIMO on WiMAX network formation; the evaluation of system performance when MIMO is applied in WiMAX system; the computation of MIMO SNR(Signal to Noise Ratio) in WiMAX system level simulation.In the aspect of the algorithm of adaptive switching between MIMO diversity and multiplexing, some typical research results are analyzed first, such as the algorithm of adaptive switching between MIMO diversity and multiplexing based on Euclidean distance of codeword by Robert W. Heath. It is found that these results are all pure theoretical, without the consideration of practical communication scheme, and can not be applied directly in practical systems. Second, an adaptive switching algorithm of MIMO diversity and multiplexing based on the power proportion of MIMO equivalent channel is proposed through the analysis of wireless communication system model by matrix theory. Finally, the simulation platform is set up based on that of ZTE Corporation. On 10MHz bandwidth of 2.5GHz frequency and under urban micro cell and suburban macro cell circumstances of SCME(Extending of Spatial Channel Model) channel model, the performances of WiMAX SISO(Single Input and Single Output), MIMO diversity, MIMO multiplexing, and the algorithm proposed are simulated. The simulation results are following:(1) Under urban micro cell circumstance of SCME channel model, compared with WiMAX SISO system, there are 0.9271Mbps, 1.6073Mbps, 1.9112Mbps gains of average sector throughput separately when MIMO diversity, MIMO multiplexing, the adaptive algorithm proposed are applied.(2) Under suburban macro cell circumstance of SCME channel model, compared with WiMAX SISO system, there are 0.9621Mbps, 0.8012Mbps, 1.4353Mbps gains of average sector throughput separately when MIMO diversity, MIMO multiplexing, the adaptive algorithm proposed are applied. When extending the cell radius by 1/6, the gains of average sector throughput are 1.5751Mbps, 0.3739Mbps, 2.1056Mbps separately. Meanwhile, when SISO and MIMO multiplexing are applied, the code error rates increase by 4.75% and 3.57%, and when MIMO diversity and the adaptive algorithm are applied, the code error rates increase less.In the aspect of the influences of MIMO on WiMAX network formation, the problems in coverage, capacity, and interference of WiMAX MIMO system are discussed and the corresponding solutions are proposed.In the aspect of MIMO SNR computation in WiMAX system level simulation, through detailed deduction, the SNR computation formulas of MIMO diversity and multiplexing are derived, and the SNR mapping method in WiMAX system is also discussed.