Coverage Analysis for Integrated Satellite-Terrestrial Downlink Networks

Integrated satellite-terrestrial networks (ISTNs) has recently been significant interest to attain synergistic gains in expanded coverage and transmission rate enhancement. Despite the potential of ISTNs, a comprehensive mathematical performance analysis framwork is lacking, so this paper introduces a tractable approach to analyze the downlink coverage performance of ISTNs, where each network operates with orthogonal frequency bands. We model the spatial distribution of terrestrial and satellite base stations (BSs) using homogeneous Poisson point processes arranged on concentric spheres with varying radii. Central to our analysis is a displacement principle that transforms BS locations on different spheres into annuli while preserving the distance distribution to the typical user. By incorporating the effects of Shadowed-Rician fading on satellite channels, we derive analytical expression for coverage in the ISTN while keeping full generality. Our key finding is that network performance depends on the density ratio of users associated with the network according to the density and the channel parameters of each network. Through simulations, we validate the precision of our derived expression.