基于NOMA的去蜂窝大规模MIMO系统上行联合信号检测

Uplink Joint Signal Detection of NOMA⁃based Cell⁃free Massive MIMO Systems

随着6G移动通信系统研究的进展,去蜂窝大规模多输入多输出(Multiple⁃input Multiple⁃output,MIMO)作为一项热点候选技术受到了广泛关注。首先建立基于非正交多址(Non⁃orthogonal Multiple Access,NOMA)的去蜂窝大规模MIMO系统模型,采用空间相关的Rician衰落信道模型以及最小化均方误差(Minimum Mean⁃Square Error,MMSE)信道估计,根据上行性能分析的理论框架及信道统计特性推导上行频谱效率的闭合表达式。其次,通过联合信号检测进一步提高系统性能。最后,通过仿真验证随着接入节点(Access Points,AP)数增大,用户被更多的AP所服务,系统频谱效率呈增大趋势,并且,增加AP处的天线数,可以使信号检测和干扰消除的空间自由度增大,从而频谱效率增大。此外,联合信号检测机制能够实现大约30%的性能提升。研究结果为NOMA辅助的去蜂窝大规模MIMO系统设计提供了理论基础,有助于未来6G移动通信系统的发展。

With the development of the research on the 6th Generation(6G)mobile communication systems,the cell-free massive multiple-input multiple-output(MIMO)technology has attracted wide attention as a candidate technology.In this paper,a spatially correlated Rician fading channel system model was established based on the NOMA-based cell-free massive MIMO.The minimum mean-square error(MMSE)channel estimation was used to derive the closed-form expression of the uplink spectral efficiency(SE)based on the theoretical framework of the uplink performance analysis and the channel statistical characteristics.Secondly,through joint signal detection,the system performance is further improved.Finally,by simulation analysis,it is verified that as the number of APs increases,users are served by more APs which leads to the increase of SE.In addition,with the number of antennas increased,the spatial freedom of signal detection and interference elimination is larger,and thus the SE is improved.Moreover,joint signal detection can achieve approximately 30%performance improvement in NOMA-based cell-free massive MIMO systems.The results provide a theoretical basis for the design of cell-free MIMO system assisted by NOMA,and contribute to the development of 6G mobile communication system in the future.