Energy-Efficient Spatial Domain Self-Interference Cancellation Method by the Addition of an RF Chain in Full-Duplex MIMO Systems

This paper addresses a multiple-input multiple-output (MIMO) full-duplex (FD) communication system. We propose an easy-to-implement, novel spatial domain self-interference cancellation (SIC) method, where an additional radio-frequency (RF) chain is implemented on the transmitter side of the FD transceiver to perform SIC only. The main idea is to transmit a specific SIC signal through the additional RF chain to the receiver of the FD system to mitigate the self-interference (SI). Based on this approach, we demonstrate that conventional MIMO precoders, such as zero-forcing (ZF) and regularized zero-forcing (RZF), can gain SIC capability within our system model, enabling FD operation of the transceiver system. In particular, we show that the ZF precoder outperforms the RZF precoder in terms of SIC. Furthermore, we assess our proposed SIC strategy in terms of energy efficiency (EE) and show through theory and simulation that our method is more energy-efficient than other existing methods for a weakly correlated communication channel. Additionally, our simulation results highlight the influence of the number of antennas dedicated to transmitting the SIC signal in our approach, providing a practical and clear understanding of the SIC performance and EE for both the ZF and RZF precoders.