Interference in LoS massive MIMO is well approximated by a Beta-mixture

In this paper, we consider the uplink in a single cell multi-user massive multiple-input-multiple-output (MIMO) system, where the multi-antenna base station (BS) serves single-antenna users. The BS is equipped with three directional linear antenna arrays, each covering one-third of the cell area. We focus on one antenna array and the corresponding sector. The users are randomly placed in the sector and transmit to the BS utilising perfect uplink power control. Assuming pure line-of-sight (LoS) channels, receiver maximum-ratio-combining (MRC) is performed at the BS. Under such a setting, we study the intra-sector interference. The single-user interference and multi-user interference are modelled by Beta and Beta-mixture distributions, respectively. The approximate interference distribution can be used to compute the coverage probability and other quantities that depend on the distribution of the signal-to-interference ratio (SIR).