Dynamic Downlink-Uplink Spectrum Sharing between Terrestrial and Non-Terrestrial Networks

TL;DR

This paper proposes a dynamic FDD band re-assignment method for 6G satellite-terrestrial networks to reduce interference and significantly improve throughput in dense deployments.

Contribution

It introduces a joint optimization framework for dynamic band assignment, user scheduling, and power control in satellite-terrestrial 6G networks, addressing interference issues.

Findings

Up to 94% throughput improvement in dense satellite deployments.

Effective interference management through dynamic FDD band re-assignment.

Enhanced system performance over conventional fixed FDD systems.

Abstract

6G networks are expected to integrate low Earth orbit satellites to ensure global connectivity by extending coverage to underserved and remote regions. However, the deployment of dense mega-constellations introduces severe interference among satellites operating over shared frequency bands. This is, in part, due to the limited flexibility of conventional frequency division duplex (FDD) systems, where fixed bands for downlink (DL) and uplink (UL) transmissions are employed. In this work, we propose dynamic re-assignment of FDD bands for improved interference management in dense deployments and evaluate the performance gain of this approach. To this end, we formulate a joint optimization problem that incorporates dynamic band assignment, user scheduling, and power allocation in both directions. This non-convex mixed integer problem is solved using a combination of equivalence transforms, alternating optimization, and state-of-the-art industrial-grade mixed integer solvers. Numerical results demonstrate that the proposed approach of dynamic FDD band assignment significantly enhances system performance over conventional FDD, achieving up to 94\% improvement in throughput in dense deployments.