Coding Algorithm For Multiuser MIMO / MIMO-OFDM Wireless Communication System Intervention

With the rapid growth of wireless communication services, the seek for the technology with higher speed and more reliability is always the research focus of academic and industry worlds. Multiple input multiple output (MIMO) can significantly improve channel capacity, and reduce bit error rate (BER). Orthogonal frequency division multiplexing (OFDM) can be efficiently against multipath fading. Therefore, MIMO and MIMO-OFDM are viewed as one of core techniques of the future wireless communication systems. In order to achieve a higher data rate and better BER performance, pre-coding can be implemented at the transmitter to suppress the interference among multiple users. This paper mainly investigates pre-coding algorithms in multi-user MIMO and MIMO-OFDM wireless communication system:1) In narrow-band multi-cell multi-user MIMO(MU-MIMO) system, singular value decomposition (SVD), channel inverse (CI), regularized CI (RCI), block diagonalization(BD), minimize mean square error(MMSE) and rate maximization(Rate-Max) are investigated. In order to imrpove data rate, an alternating iterative structure of maximizing sum-rate and power allocation is proposed. The simulation results show that:the proposed iterative structure has significant substantial sum-rate gains over other precoders.2) In wide-band MU-MIMO-OFDM system, the subcarrier-based and the N-subcarrier pre-coding system models where N is the total number of subcarriers are introduced, and six classical linear precoders are investigated, and an improved low-complexity Max-SLNR scheme is proposed. The simulation results show that:Max-SLNR outperforms CI, RCI, BD and MMSE; in the presence of high Doppler shift, these N-subcarrier precoders are superior to these subcarrier-based ones; the proposed Max-SLNR can signficantly reduces the complexity at the cost of some sum-rate and BER performance losses over Max-SLNR.3) In order to further enhance the data rate of wide-band MU-MIMO-OFDM system, three nonlinear precoders:dirty paper coding (DPC), decision feedback equalization (DFE) and Tomlinson-Harashima precoding (THP) are investigated in the system model built in2). The simulation results show that:the nonlinear precoders achieve the better sum-rate performance compared with linear ones; but their BER performances are poor at low SNR region, as SNR increases, their performances approach that of SVD.