Modelling interference in high altitude platforms with 3D LoS massive MIMO

Abstract

In this paper, we study a three-dimensional (3D) massive multiple-input-multiple-output (MIMO) system where a horizontal planar antenna array hovers in the sky, serving multiple single-antenna users in a cell on the ground. We consider the uplink where the users transmit to the antenna array utilising perfect uplink power control. Assuming pure line-of-sight (LoS) propagation conditions, the planar array performs receiver maximum-ratio-combining (MRC). We adopt a 3D freespace propagation channel model, which enables us to exploit both the azimuth and elevation dimensions of the space. Under such a setting, we analyse the intra-cell uplink interference. The effective single-user interference and total interference can then be modelled by Beta and Beta-mixture distributions, respectively. In particular, we point out that the height of the hovering antenna can be adjusted to minimise the interference in the system, and thus optimise all the signal-to-interference ratio (SIR) related performance metrics such as coverage and average throughput.