Full-Duplex Massive MIMO Relaying Over Spatially Correlated Rician Channel With Phase Shifts

We analytically study a multi-pair two-way full-duplex (FD) massive multiple-input multiple-output relay system over a spatially correlated Rician channel with unknown phase shifts. Most of the existing literature ignores the line-of-sight (LoS) phase shift, which arises due to user mobility and hardware impairments. We analyze the impact of LoS phase shift on the spectral efficiency (SE) of the system by considering two different channel estimators: i) phase-unaware linear minimum mean square error (LMMSE) and ii) phase-aware MMSE. We also formulate the asymptotic SE expressions for three different power scaling schemes considering zero-forcing receiver/zero-forcing transmitter processing at the relay. We numerically show the impact of unknown phase shifts on the SE of the system. Finally, we highlight the impact of i) loop interference due to the FD operation and ii) pilot power on the sum-SE.