Spectral and energy efficiency for massive MIMO multi-pair two-way relay networks with ZFR/ZFT and imperfect CSI

This paper investigates a massive MIMO multi-pair two-way relay system, where K-pair users exchange information within communication pair, with the help of a shared amplify- and-forward (AF) relay station (RS). Large scale antenna array is equipped at the RS and each user has a signal antenna. The RS adopts the zero-forcing reception/zero-forcing transmission (ZFR/ZFT) beamforming. The imperfect channel state information (CSI) is considered, and the impact of channel estimation errors on system performances is investigated. Based on two power scaling schemes, we obtain the asymptotic spectral efficiency and asymptotic energy efficiency of the considered system. Our results reveal that when the number of RS antennas grows without bound, the small-fading can be averaged out; the additional noise and residual self-interference generated by channel estimation errors will completely disappear; and inter-pair interference will also vanish. Consequently, the simulation results will be confirmed by Monte-Carlo simulation method.