Joint Trajectory and Resource Optimization for Interference Management in Space-Air-Ground Integrated Networks Under Probabilistic LoS Channels

Abstract

This study explores interference coordination for space-air-ground integrated networks under probabilistic line-of-sight (LoS) channel models, where the LoS probability of a wireless channel is statistically modeled based on the elevation angle between an unmanned aerial vehicle (UAV) and a ground node (GN). Unlike conventional approaches that simplify the model by neglecting either LoS or non-LoS (NLoS) channel components, we jointly optimize user scheduling, transmit power, and three-dimensional trajectory while fully accounting for both components. The objective is to maximize the minimum average spectral efficiency (SE) among GNs while ensuring the required SE for earth stations (ESs) served by satellites. Given the nonconvexity of the optimization problem, we decompose it into four subproblems and apply a successive convex approximation to make each subproblem convex with respect to the relevant optimization variable. Subsequently, we propose a low-complexity algorithm based on the block coordinate descent method to iteratively determine the optimal solution for each convex subproblem. Extensive simulations under various scenarios confirm that the UAV optimizes its horizontal and vertical trajectories to increase the LoS probability of the signal channel and the NLoS probability of the interference channel. This allows the UAV to serve GNs with high SE while reducing interference to the ESs. The results also demonstrate that the proposed scheme outperforms baseline schemes in terms of average SE by jointly optimizing the three-dimensional trajectory and communication resources. © 1972-2012 IEEE.