Performance Analysis for Training-Based Multipair Two-Way Full-Duplex Relaying With Massive Antennas

This paper considers a multipair two-way amplifyand-forward (AF) relaying system, where multiple pairs of fullduplex users are served via a full-duplex relay with massive antennas, and the relay adopts maximum-ratio combining/maximumratio transmission (MRC/MRT) processing. The orthogonal pilot scheme and the least square method are first exploited to estimate the channel state information (CSI). When the number of relay antennas is finite, we derive an approximate sum rate expression which is shown to be a good predictor of the ergodic sum rate, especially with a large number of antennas. Then, the corresponding achievable rate expression is obtained by adopting another pilot scheme which estimates the composite CSI for each user pair to reduce the pilot overhead of channel estimation. We analyze the achievable rates of the two pilot schemes and then show the relative advantages of the two methods. Furthermore, power allocation strategies for users and the relay are proposed based on sum rate maximization andmax-min fairness criterion, respectively. Finally, numerical results verify the accuracy of the analytical results and show the performance gains achieved by the proposed power allocation.