Spectral Efficiency Analysis of Multi-cell Multi-user Massive MIMO over Channel Aging

To achieve the expected attractive potential of massive multiple-input multiple-output (MIMO), accurate match between the receiver and the actual channel is necessary. Due to the channel aging, this kind of mismatch appears in the vast majority of practical propagations. Consequently, the impact of channel aging for massive MIMO is investigated in this study. The authors first propose an equivalent estimated channel model by considering the inevitable time-varying nature of channels in realistic mobile communications. Then, they obtain the achievable uplink rate based on the proposed equivalent channel models. In particular, the closed-form expression of the asymptotic uplink rate is derived. Different from the existing works, this study considers the joint multi-cell minimum-mean-squared-error (MMSE) channel estimator and MMSE receiver for massive MIMO systems over aging channels. Through the simulation, it demonstrates that adopting massive MIMO can compensate for the performance loss caused by channel aging. In addition, this pstudy gives some insights into the system design: to achieve the best performance, system with higher-mobility terminals should be operated with more pilot resources, and it can support more users, moreover, the optimal number of users supported in a cell is less than half of the coherence time interval.