Effect of phase noise on digital self-interference cancellation in wireless full duplex

Abstract

Oscillator phase noise in a full duplex radio causes the mismatch between the self-interference (SI) signal and the cancelling signal, and thus degrades performance of the digital SI cancellation (SIC). In this paper, we analyze the effect of phase noise on digital SIC in wireless full duplex. We consider an OFDM-based full duplex radio corrupted by the phase noise at both the transmitter and the receiver, which are modeled as independent Wiener processes. A closed-form expression for the cancellation ability of a common digital SIC scheme is derived, in terms of the interference-to-noise ratio (INR), the SI subcarrier spacing and the oscillator's 3dB coherence bandwidth. The theoretical analysis and simulations reveal that the digital SIC ability degrades with the increase of the ratio of the oscillator's 3dB coherence bandwidth to the signal bandwidth, which determines the upper bound of the digital SIC ability.