Full-Duplex Meets Multiuser MIMO: Comparisons and Analysis

Efficient utilization of wireless communication resources and increases in the capacity of the communication networks have become very crucial claims for next-generation cellular networks. Full-duplex (FD) is a very promising technique that allows for the efficient use of wireless communication resources, given that the self-interference level can be suppressed to an acceptable level. In this paper, we consider a simple FD communication system, consisting of one FD access point (AP) and two half-duplex (HD) mobile users, and investigate when it is more advantageous for the communication network to operate in FD or HD multiuser multiple-input multiple-output (MIMO) mode. Since FD transmission is degraded by self-interference while HD suffers from spatial correlation between MIMO antennas, which causes rate loss, we study the effect of both the self-interference cancelation parameter at the FD AP and the mutual distance between the HD users on FD performances and the effect of the spatial correlation coefficient on HD MIMO. Afterward, a switching criterion is proposed, which chooses the operation mode that maximizes the downlink channel capacity while maintaining the uplink channel capacity at a certain level. Subsequently, based on our study of the system's parameters that affect the performance of both FD and HD, theoretical thresholds for these parameters are derived. Finally, numerical analysis is presented, verifying the validity of the optimization problem solution and the derived thresholds.