Proximity co-located massive MIMO systems over correlated Rician fading channels

Abstract

This paper considers the downlink transmission in a single-cell proximity co-located massive MIMO (PC-MIMO) system, in which antennas of the base station (BS) are divided into multiple antenna units (AUs) and these AUs are connected to a backhaul processor unit (BPU). The AUs are geographically deployed very close to the BPU which controls them to serve all users in the cell. Considering correlated Rician fading channels, we derive a closed-form expression of the sum spectral efficiency under the maximum-ratio transmission and statistical channel state information at each user. Based on the obtained expression, it is shown that as the number of AUs approaches infinity, the sum spectral efficiency approaches a constant value. Furthermore, we also give a closed-form expression of the average sum spectral efficiency when the arrival angles to the users seen from the AUs are varying. For the cases of correlated Rayleigh fading and uncorrelated Rician fading, we show how to find the number of antennas at each AU to maximize the average sum spectral efficiency when the total number of antennas at the BS is fixed.