Downlink Multiuser Massive MIMO in Rician Channels under Pilot Contamination

In this paper, we investigate uplink channel estimation and multiuser downlink transmission of a massive MIMO time-division duplex system in the presence of pilot contamination, where the base station (BS) with M antennas communicates with N single-antenna users in a cell. We assume that all channels are affected by Rician fading. We also assume that angles of arrival from users to the BS are different. We first analyze the impact of pilot contamination on the channel estimation, based on which we derive a tight sum-rate approximation. We also obtain the asymptotic sum-rate for large Rician K-factor in the large signal to noise ratio regime. Furthermore, we examine the impact of the Rician K-factor on the sum-rate of the system, showing that the sum-rate increases as K-factor increases.