Realistic Cooperative Strategies Based on Dynamic Spectrum Sharing for Integrated Satellite-Terrestrial Networks

Integrated satellite-terrestrial networks (ISTNs) are increasingly recognized for their global communication. However, much of the existing research is focused on simplified ISTNs, where the cooperative strategies between satellites and base stations (BSs) are not easily applicable to real-world scenarios. There is a pressing need to investigate more realistic and complex ISTNs to address this gap. In this context, a distributed BS strategy for scenarios with uniformly distributed terminals and a centralized BS strategy for scenarios with unevenly distributed terminals are proposed. Additionally, these BS strategies are combined with three distinct spectrum sharing modes for enhancing access flexibility. Due to supporting non-orthogonal transmissions and enhancing interference management capabilities, rate-splitting multiple access is adopted to efficiently serve numerous terminals using finite communication resources. For these strategies, the corresponding max-min rate optimization problems are developed, and then an alternating optimization (AO) method is introduced utilizing weighted minimum mean square error to resolve the non-convex challenges in overlay spectrum sharing. Moreover, an adaptive power control method, leveraging the AO algorithm, is designed to navigate the non-convex challenges in underlay spectrum sharing. Simulation outcomes confirm that the proposed schemes yield considerable performance enhancements compared to various standard schemes.