Research On The Multi-user Detection Algorithms In MIMO OFDM System

The combined MIMO and OFDM can increase data transmission rate for several times and simultaneously overcome inter-symbol interference and multi-path fading of wireless channel. Meanwhile, it is the key technology in the next generation communication. However, the performance of MIMO-OFDM system may seriously degrade in the presence of multiple access interference (MAI). Therefore, it is of importance to research on multi-user detection in multi-user MIMO-OFDM system.The principle of technology of Space-Time Block code (STBC) and MIMO-OFDM system is firstly presented in this paper. Thereafter, the model of multi-user MIMO-OFDM system is designed. In this paper, linear multi-user detection algorithm and interference cancellation multi-user detection algorithm are fully discussed, such as zero-forcing (ZF), minimum mean-square error (MMSE), the combined MMSE and Successive Interference Cancellation (SIC), Parallel Interference Cancellation (PIC), and the combined MMSE and Parallel Interference Cancellation (MMSE-PIC). Simulations are taken to verify and compare the performance of each algorithm. Meanwhile, the two-step interference cancellation algorithm is proposed on the basis of former research. The results of simulation show that the two-step interference cancellation algorithm, compared to MMSE algorithm, can achieve better performance without increasing the complexity. We study the minimum bit error rate (MBER) multi-user detection algorithm and then use the algorithm in MIMO-OFDM system; we make an analysis of the performance of the MBER algorithm by simulation. The results of simulations show that the MBER multi-user detection algorithm with the goal of minimum bit error rate directly can achieve better performance than MMSE algorithm with the goal of minimum mean square error, and the MBER algorithm's complexity is similar to MMSE algorithm.