基于分布式混合CSIT的MIMO X网络自由度分析

在M×N用户MIMO X网络中，发射端信道状态信息（CSIT）类型会影响系统总自由度（sum-DoF）.为逼近系统总自由度外界，设计MIMO X网络对称天线配置下的多阶段分布式空时干扰对齐（DSTIA）方案；推导具有分布式特性的基于混合CSIT—过期（outdated）和当前（current） CSIT的预编码矩阵闭式解；分析CSI反馈时延、网络节点数和配置天线数对MIMO X网络总自由度的影响.理论和数值分析表明，在分布式混合CSIT条件下，DSTIA方案能充分消除用户间干扰，获得更高的自由度，缩小可达界与外界的差距，提高系统可达速率.

DoF Analysis of the MIMO X Network with Distributed Hybrid CSIT

In the context of M×N user multiple-input multiple-output (MIMO) X network,the different types of channel state information at the transmitters (CSIT) have impacts on the sum of degrees of freedom (sum-DoF).To approximate to the sum-DoF outer bounds,we propose a multiphase distributed space-time interference alignment (DSTIA) scheme for the MIMO X network with symmetric antenna configurations.We derive the closed-form solution of precoding matrix based on hybrid CSIT (i.e.,outdated and current CSIT) with distributed characteristics,while revealing the impact on how the CSI feedback delay,as well as the number of transmitters/receivers and the number of antennas affect the sum-DoF of the MIMO X network.Theoretical and Analytical results show that,with distributed hybrid CSIT,DSTIA scheme can achieve better sum-DoFs by eliminating inter-user interference perfectly,as well as tightening DoF gap and improving the achievable rates of system.