多输入多输出（multiple input multiple output，MIMO）多向中继信道（multiway relay channel，mRC）的自由度（degree of freedom，DoF）分析是近几年的研究热点。研究半双工通信下两个用户集群，每个用户集群中K个用户的MIMO mRC可达到的DoF。其中，考虑完整数据交换模型，即用户集群中每个用户希望与此集群中其他所有用户交换信息。结合物理层网络编码，并利用信号对齐技术设计用户端和中继端的处理矩阵，优化系统可达到的DoF。通过对上行和下行链路分别设计信号对齐，并优化时隙分配，得到半双工通信下系统可达到的DoF。另外，当上行和下行时隙相等时，将结果推广到全双工通信，并验证了该信号对齐方案可以达到全双工通信目前最优的结果。
Recently, much research interest was focused on the degree of freedom (DoF) analysis of multiple input multiple output (MIMO) multiway relay channel (mRC). In this work, we investigate the achievable DoF of the half duplex MIMO mRC with two clusters each of which contains K users. Also, we focus on full data exchange model, which means that each user in a cluster wants to exchange information with all the other users in the same cluster. To achieve efficient DoF, signal alignment techniques are developed to jointly construct the beamforming matrices at the user and the relay. Also, we design signal alignments for uplink and downlink, respectively, as that the uplink and downlink are asymmetry in the full data exchange model. Combining with the optimized uplink and downlink time allocations, we derive an achievable DoF for the half duplex model. Further, we expand our analysis to full duplex model considering equal uplink and downlink time allocations, and show that one can use our signal alignment scheme to obtain the optimized achievable DoF in full duplex model.
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