Coverage Analysis of Large-Scale HAPS Networks Using Directional Beams

High Altitude Platform Stations (HAPS) are regarded as pivotal components within non-terrestrial networks (NTN) to achieve global seamless connectivity and interconnect the NTN nexus. In this article, we propose a spherical stochastic geometry-based analytical framework for the coverage performance evaluation of HAPS networks. Considering the significant influence of directional antenna gain on interference evaluation, we analyze coverage performance under a general channel model suitable for any beam patterns. Analytical expressions of the uplink and downlink coverage probabilities in cellular and cell-free networks are provided respectively and their accuracy are verified by Monte Carlo simulation. Furthermore, the influences of beam-related parameters and HAPS/user distribution on coverage probability are studied. Finally, several factors that align with the analytical framework of this article are discussed. For HAPS networks, the simulation results demonstrate that cellular architecture outperforms cell-free architecture and that directional antennas are effective at increasing uplink coverage by reducing interference.