Sum-rate performance and impact of self-interference cancellation on full-duplex wireless systems

We consider full-duplex (FD) bidirectional communication between a pair of nodes and investigate the impact of residual self-interference on sum-rate performance. We first analyze a situation where channel state information is available only at receiver (CSIR). For this case, we derive an exact expression and a lower bound to the sum-rate performance of FD and hence characterize the effect of residual self-interference. The study shows that, FD sum-rate performance is limited by the effective signal-to-residual self-interference power ratio (effective SIR). In particular, for a fixed effective SIR, FD achieves almost twice the sum-rate of half-duplex (HD) in low signal-to-noise ratio (SNR) regimes whilst FD performance is surpassed by HD in high SNR regions. A closed-form approximation to this crossover SNR is derived. We then investigate the sum-rate of FD assuming channel state information is available to both transmitter and receiver (CSIT). Comparison of FD sum-rates of CSIR and CSIT shows that, in low SNR regions, a significant benefit can be achieved with CSIT while the gain is small in high SNR levels.