On Performance Of Massive MIMO With Spatial Correlation

As an extension of traditional MIMO system, Massive MIMO, which can greatly improve the system throughput and power efficiency, has become a hot research topic of next generation wireless communications. However, Massive MIMO system needs to use large number of antennas to serve limited number of user terminals. This increases the size of antenna array, which may increase the difficulty of installation of the base station. In this thesis, we focus on the impact of spatial correlation on the performance of massive MIMO. Then we investigated the massive MIMO based on dual-polarized antennas, which may reduce the size of the antenna array without performance degradation.Firstly, we review the essential features of massive MIMO, including TDD based uplink and downlink transmission, pilot contamination, and transmitter side precoding, etc.Secondly, we analyzed and simulated the negative impact of spatial correlation on the performance of massive MIMO. We connected the spatial correlation with the antenna array structure in the base station, and simulated the per user rate with and without space limitation at the base station. Through analysis, we found that for limited antenna array space, as we increase the number of antennas, the spatial correlation will increase and per user rate will saturate.Thirdly, under the condition of exponential correlation, we analyzed the performance of massive MIMO based on single-polarized antenna array. We theoretically prove that with exponential correlation, as the number of antennas approaches infinity, the asymptotic SIR is the same as that without spatial correlation. We further proved this theoretic result by simulation.Lastly, we analyzed the performance of massive MIMO based on dual-polarized antenna array; we showed its capability of reducing the antenna array size compared with the single-polarized antenna array.