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

2025-11-11

AI Summary

To address spectrum-sharing interference arising from dense low-Earth-orbit (LEO) satellite deployments in 6G integrated space–ground networks, this paper proposes a dynamic Frequency Division Duplex (FDD) band reconfiguration mechanism—the first to introduce dynamic uplink/downlink band reallocation for satellite interference management. The method jointly optimizes band assignment, user scheduling, and bidirectional power control, thereby overcoming the inflexibility of conventional fixed-duplex FDD and enabling agile, cross-domain resource coordination between non-terrestrial and terrestrial networks. Leveraging equivalent transformations and an alternating optimization framework, combined with an industrial-grade mixed-integer programming (MIP) solver, the approach efficiently handles the underlying non-convex mixed-integer optimization problem. Simulation results demonstrate that, under dense deployment scenarios, the proposed scheme achieves up to a 94% throughput gain over conventional FDD, significantly enhancing spectral efficiency and interference mitigation capability in 6G integrated space–ground networks.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• User Modeling, Personalization and Recommendation: Federated recommendation systems and personalization

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.

Problem

• Managing severe interference in dense satellite mega-constellations
• Overcoming limited flexibility of conventional frequency division duplex systems
• Optimizing spectrum sharing between terrestrial and non-terrestrial networks

Innovation

• Dynamic FDD band assignment for interference management
• Joint optimization of band assignment and scheduling
• Mixed integer solvers with alternating optimization