基于STBC的MIMO OFDM系统中的I/Q不平衡及CFO的联合均衡策略

摘要

Based on the STBC scheme, the combined effect of the transmitter and receiver I/Q imbalance, the front-end filter unmatch, CFO and frequency selective channel distortion for the presence at the same time in MIMO OFDM com-munication system was intensively studied , and an applicable joint equilibrium strategy was also proposed. The concrete implementation is that a frequency domain equalizer was firstly obtained through the analysis of the only presence of the transmitter I/Q imbalance and multipath channel interference in MIMO OFDM system. And then considering on the si-multaneous presence of receiver I/Q imbalance and CFO, two time domain equalizers were also obtained. Finally, these time domain equalizers were transformed into the frequency domain, combined with frequency domain equilibrium technology to eliminate the transmitter I/Q imbalance and multipath channel interference. A comprehensively joint equi-librium technology, namely frequency domain per-tone equalizer, was proposed. The simulation results show that the frequency domain per-tone equilibrium technique for the proposed MIMO OFDM system can be extended to other higher order STBC system, and the BER performance of the system after equilibrium using the proposed equilibrium technique is improved obviously.%基于STBC方案，针对MIMO OFDM通信系统中同时存在发射机和接收机I/Q不平衡、前端滤波器失配、CFO和频率选择性信道失真的组合影响进行了深入研究，并提出了一种适用的联合均衡策略；具体实现是首先通过对MIMO OFDM系统中只存在发射机I/Q不平衡和多径信道干扰的分析，得到一种频域均衡器；然后再考虑同时存在接收机I/Q不平衡和CFO的情况，得到了2个时域均衡器；最后把2个时域均衡器变换到频域，并结合消除发射机I/Q不平衡和多径信道干扰的频域均衡技术，提出了一种全面的联合均衡技术即频域子载波均衡器。仿真结果表明，针对MIMO OFDM系统提出的频域子载波均衡技术不仅能扩展到其他高阶STBC系统，而且使均衡后的系统BER性能得到了明显的提高。