The Research On Limited Feedback Precoding Technology For Multi-carrier Spatial Multipexing Systems

MIMO technology, employing multiple transmitting antennas and multiple receivingantennas, can improve the throughput and the BER performance of wireless communicationsystem using space diversity without increasing the system bandwidth and the extra power,and it’s suitable for high speed and large capacity demand of future mobile communicationsystem. OFDM technology is a special kind of multi-carrier modulation technique, thistechnology achieves high spectral utilization ratio and overcome the frequency selectivefading caused by multi-path propagation. MIMO-OFDM, combining MIMO and OFDM, cannot only achieve high rate and large capacity in limited bandwidth, but also can improve theability of the system to against noise and multi-path. MIMO-OFDM technology has becomeone of the core technologies of the next mobile communications. Focus on the errorpropagation effect of multi-carrier layered space-time scheme and higher complexity inperformance, this paper mainly studies the limited feedback pre-coding technology based onchannel state information and code in MIMO-OFDM system. The text can be divided intofive parts; concrete work and innovation are as follows:This paper first introduces the research background and significance, elaborates theresearch present situation about the MIMO multi-carrier technologies, limited feedbackpre-coding technique at home and abroad; then introduces the multi-carrier layered space-timetheory and gives the basic model and signal representation of the MIMO-OFDM system. Thispaper mainly studies the limited feedback pre-coding technology based on channel stateinformation and code in MIMO-OFDM system: Focus on imperfect channel pre-codingtechniques, the different Linear Pre-coding and nonlinear pre-coding methods are simulatedand analyzed, the linear pre-coding has the similar performance compared to the traditionallinear detection, but the complexity of receiver effectively is reduced, the nonlinearpre-coding methods can effectively eliminate the error propagation effect of multi-carrierlayered space-time scheme and can significantly improve the system BER performance; focuson the partial channel state information limited feedback pre-coding technology, the limitedfeedback pre-coding method based on multi scale wavelet transform is presented, this methodcan reduce feedback cost largely, at the same time, the BER performance of the system can bewell approximated to traditional pre-coding method. Then this paper studies the limitedfeedback pre-coding method based on codebook, considering the problem of feedback cost and performance loss for limited feedback spatial multiplexing with limited feedback, animproved nonlinear detection method based on limited feedback pre-coding for spatialmultiplexing is proposed. Exploiting the correlation between sub-carrier channels of OFDM,and only a part channel of sub-carrier should be estimated, The corresponding criteria is usedfor select optimal codeword from the Grassmannian codebook at the receiving according tothe channel state information, and feedback the pre-coding word index to the transmitter, thenonlinear iteration detection is used at the receiving to compensate for the performance lossdue to the limited feedback. The last part is the summary and prospect.