Mimo System Precoding Technology Research

Multiple-input multiple-output (MIMO) technology used multiple antennas in the transmitter and receiver. It can increase channel capacity and improve the system performance by diversity and multiplexing without increasing system transmission power and signal bandwidth of the circumstances. In this paper, first we were familiar with the MIMO channel capacity and the corresponding theoretical of Rayleigh channel simulation, analyzed and discussed in the ideal channel state information (CSI) under the single-user and multi-user communication scenarios when both linear and nonlinear precoding and receiver were used to zero forcing (ZF) criterion and the minimum mean square error (MMSE) criterion of the processing algorithms. Then consider the non-ideal CSI multi-user MIMO system under the nonlinear THP precoding.By analysis and discussion of the precoding method in the single-user MIMO system, we could obtained that the MMSE processing algorithm was better than the ZF algorithm in BER performance. THP precoding was also studied to further improve the system performance. It could achieve the feedback operation by using QR decomposition of channel matrix. The same simulation results were also gotten. Then this paper studied the block diagonalization algorithm method, which could eliminate interference between users. The algorithm of ZF-THP decomposed by QR was analyzed in multi-user MIMO system. Simulation results showed that this algorithm could improve the system BER performance, but the BER performance was greatly different between users.Finally, this paper analyzed the THP precoding in the multiple users virtual MIMO system in non-ideal CSI, which composed by single antennas of multiple users. The formulae of channel estimation error on system BER performance were derived. And the formulae showed that non-ideal CSI could affect BER performance of the system. In order to overcome the affect of channel estimation error on system BER performance, we used a channel sorting algorithm–"the best priority (best-first) sorting algorithm"to improve the system BER performance.