Multi-Pair Two-Way Massive MIMO AF Full-Duplex Relaying With Imperfect CSI Over Ricean Fading Channels

This paper investigates a multi-pair two-way massive MIMO amplify-and-forward full-duplex relay (FDR) system over Ricean fading channels, where multiple pairs of full-duplex users exchange information within pair through a full-duplex relay with a very large number of antennas (M for transmission and M for reception). First, the zero-forcing reception/zero-forcing transmission and maximum-ratio combining/maximum-ratio transmission processing matrices with imperfect channel state information at the relay are presented. Then, the corresponding asymptotic expressions (in M) of the end-to-end signal-to-interference-plus-noise ratio are derived. Finally, the asymptotic spectral efficiency (SE) and energy efficiency (EE) at the general power scaling schemes when the number of the relay antennas tends to infinity is analyzed. Theoretical analyses and simulation results show that, when M → ∞, the effects of channel estimation error, the self-loop of each user as well as the relay, inter-user interferences, the noise at users and the relay can be eliminated, respectively, if the power scaling scheme is properly selected. Besides, the considered multi-pair two-way FDR outperforms the multi-pair two-way half-duplex relaying on SE and EE performances when M is large. Moreover, a low complexity power control scheme is proposed to optimize the SE and we analyze the impact of the number of user pairs on the SE.