Research On Adaptive Transmission Strategies For MIMO Wireless Communications

New generation cellular mobile communication needs high speed and reliable data transmission in mobile wireless environment, so technologies with high spectrum efficiency are needed to provide higher transmitting rate and system capacity in limited spectrum. MIMO (Multiple Input Multiple Output) is that technology, which has become the key technology in the next generation mobile communication. MIMO takes advantage of the space resource to improve system capacity greatly without the increasing of spectrum resource and transmitting power of antennas, meanwhile, it can improve the reliability of channels and decrease the BER. The former utilizes spatial multiplexing gain, such as V-BLAST, and the latter utilizes diversity gain, such as STBC, provided by MIMO channels. In order to guarantee the 50-100Mbps data rate in new generation cellular mobile communication and fit for TDD physical layer design, this article mainly researches into several primary transmission strategies, including V-BLAST system, STBC(Space-Time Block Coding)+V-BLAST and V-BLAST with antenna selection. Simulation results prove that whether STBC+V-BLAST or V-BLAST with antenna selection, they can obtain obvious performance improvement in contrast to pure V-BLAST system. More important, with the same ZF receiver, we can see that the transmission strategy of V-BLAST with antenna selection is better than the strategy of STBC+V-BLAST during the observed SNR range. So, considering the various requirements of the two ways, we choose V-BLAST with antenna selection as the final transmission strategy. Based on this, we study antenna selection algorithm, especially the algorithm fit for V-BLAST system further for more performance improvement. This article put forward an antenna selection algorithm based on sub-optimal sorting and QR decomposition, which takes into account the impacts of ordering and cancellation. Simulation results show that the proposed algorithm behaves well whether in outage capacity or in BER performance and the complexity is suitable. So this is an attractive antenna selection algorithm.