  In this paper, we investigate optimal downlink power allocation in massive
multiple-input multiple-output (MIMO) networks with distributed antenna arrays
(DAAs) under correlated and uncorrelated channel fading. In DAA massive MIMO,
the base station (BS) consists of multiple antenna sub-arrays. Notably, the
antenna sub-arrays are deployed in arbitrary locations within a DAA massive
MIMO cell. Consequently, the distance-dependent large-scale propagation
coefficients are different from a user to these different antenna sub-arrays,
which makes power control a challenging problem. We assume that the network
operates in time-division duplex mode, where each BS obtains the channel
estimates via uplink pilots. Based on the channel estimates, the BSs perform
maximum-ratio transmission in the downlink. We then derive a closed-form
signal-to-interference-plus-noise ratio (SINR) expression, where the channels
are subject to correlated fading. Based on the SINR expression, we propose a
networkwide max-min power control algorithm to ensure that each user in the
network receives a uniform quality of service. Numerical results demonstrate
the performance advantages offered by DAA massive MIMO. For some specific
scenarios, DAA massive MIMO can improve the average per-user throughput up to
55%. Furthermore, we demonstrate that channel fading covariance is an important
factor in determining the performance of DAA massive MIMO.
