Interference Exploitation in Full-Duplex Communications: Trading Interference Power for Both Uplink and Downlink Power Savings

This paper considers a multiuser full-duplex (FD) wireless communication system, where an FD radio base station (BS) serves multiple single-antenna half-duplex uplink and downlink users simultaneously. Unlike conventional interference mitigation approaches, we propose using knowledge of the data symbols and the channel state information (CSI) at the FD radio BS to exploit the multi-user interference constructively rather than to suppress it. We propose a multi-objective optimization problem (MOOP) via the weighted Tchebycheff method to study the tradeoff between the two desirable system design objectives, namely the total downlink transmit power and the total uplink transmit power, at the same time ensuring the required quality-of-service (QoS) for all users. In the proposed MOOP, we adapt the QoS constraints for the downlink users to accommodate constructive interference for both generic phase shift keying modulated signals and for quadrature amplitude modulated signals. We also extended our work to a robust design to study the system with imperfect uplink and downlink CSI. The simulation results and analysis show that significant power savings can be obtained. More importantly, however, the MOOP approach here allows for the power saved to be traded off for both uplink and downlink power savings, leading to an overall energy efficiency improvement in the wireless link.