Full-Duplex Amplify-and-Forward Relaying under I/Q Imbalance

Abstract

A major performance limiter in amplify-and-forward (AF) full-duplex (FD) relaying is the high level of residual self-interference (SI) due to the imperfect estimation of the effective self-interfering channel. One primary obstacle that contributes to the ineffectiveness of estimating the effective SI channel is the transceiver's radio-frequency (RF) impairments. In this paper, we consider the effect of in-phase/quadrature imbalance (IQI) on the process of SI cancellation in FD AF transceivers. We model the cumulative SI as a function of IQI, and thoroughly analyze the stability of the performance of the relay by analyzing the different transmission parameters and configurations that guarantee the stability of the system. In particular, depending on the RF impairments of the relay's transceiver, the wireless channel conditions, and the channel estimation accuracy, the relay's maximum amplification factor and transmission power that limit the residual SI power and prevent the system oscillations are analytically derived and verified by Monte-Carlo simulations. Finally, we show that the average SI power is bounded by a sum of scaled Gamma functions.