Impact of Channel Estimation Error on the Performance of Amplify-and-Forward Two-Way Relaying

In this paper, the impact of channel-state information (CSI) estimation error on the performance of an amplify-and-forward two-way multiple relay network has been investigated. In contrast to the existing literature, which assumes perfect self-interference cancellation, we consider imperfect self-interference cancellation at both sources that exchange information through multiple relays, and maximal-ratio combining is then applied to improve the decision statistics under imperfect signal detection. We derive the effective signal-to-noise ratio (SNR) subject to noisy channel estimation, and based on this SNR, the system outage probability is given. In addition, we derive the closed-form expression of the average system bit error rate (BER) and the asymptotic expressions for both outage probability and BER. Furthermore, instead of employing all relays, we examine the impact of imperfect CSI on a single relay selection (RS) scheme. To mitigate the negative impact of imperfect CSI, we show that power allocation (PA), by minimizing either the outage probability or the BER, can suitably be cast as the geometric-programming problem. Numerical results validate the correctness of the derived expressions and show that the adaptive-PA scheme outperforms the equal-PA scheme under the aggregated effect of imperfect CSI.