非对称毫米波大规模MIMO系统信道特性研究

为了满足下一代无线通信的需求，基于最近提出的非对称毫米波大规模多输入多输出(multipleinput multiple-output, MIMO)系统架构，研究了非对称毫米波大规模MIMO系统信道特性——信道非对称性. 根据非对称毫米波大规模MIMO系统架构和影响毫米波信道非对称性的主要因素，提出了刻画上下行信道非对称性的新参数——非对称因子. 同时利用实验室自行研发的射线跟踪平台对非对称毫米波信道进行仿真分析. 结果表明，基站收发天线阵列配置不同是导致信道非对称性的根本原因，复杂的传播环境使得这种非对称性更加突出，严重情况下室内场景非对称因子可达到?30 dB左右. 同时室外视距(line-of-sight, LoS)和非视距(non-line-of-sight, NLoS)场景下的非对称因子累积分布函数(cumulative distribution function, CDF)与高斯分布拟合程度较好，而NLoS场景下明显比LoS场景下的非对称因子小. 因此，非对称因子能够直观地描述出不同场景中上下行信道的非对称程度，而且非对称毫米波大规模MIMO系统也应以场景为导向进行信道特性分析.

Research on channel characteristics of asymmetric millimeter-wave massive MIMO systems

In order to meet the needs of next-generation wireless communications, based on the asymmetric millimeter-wave massive multiple-input multiple-output (MIMO) system architecture proposed recently, the channel characteristics of asymmetric millimeter-wave massive MIMO systems-channel asymmetry are studied. According to the asymmetric millimeter-wave massive MIMO system architecture and the main factors affecting the asymmetry of the millimeter-wave channel, a new parameter describing the asymmetry of the uplink and downlink channels-the asymmetry factor is proposed. At the same time, a ray tracing platform developed by the laboratory is used to simulate and analyze asymmetric millimeter-wave channels. The results show that the different configuration of the base station transceiver antenna array is the basic reason of channel asymmetry. The complex propagation environment makes this asymmetry more prominent. In severe cases, the asymmetry factor in indoor scenario can reach about ?30 dB. At the same time, the cumulative distribution function (CDF) of asymmetric factor in the outdoor line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios fits well with the Gaussian distribution, and the asymmetric factor in the NLoS scenario is obviously smaller than that in the LoS scenario. Therefore, the asymmetry factor can intuitively describe the asymmetry degree of the uplink and downlink channels in different scenarios, and the analysis of the asymmetric millimeter-wave massive MIMO system channel characteristics should also be scenario-oriented.