RSRP-Driven Efficient Spectrum Sharing for 6G NTN-TN Integrated Networks

The integration of non-terrestrial network (NTN) and terrestrial network (TN) is a key trend towards realizing ubiquitous 6G connectivity. To efficiently address spectrum scarcity in NTN-TN integrated networks, a crucial mechanism is underlay spectrum sharing. However, the densely deployed terrestrial base stations (BSs) surrounding the NTN service area lead to severe co-frequency interference (CFI), which impairs NTN uplink (UL) transmission even when applying reverse pairing, an effective static interference mitigation mechanism [1]. We therefore introduce an underlay spectrum sharing framework designed for a multibeam low Earth orbit (LEO) satellite system. To optimize TN spectrum utilization while guaranteeing a predefined NTN throughput requirement within this framework, we propose a greedy heuristic predicated on reference signal received power (RSRP) measurements obtained by TN BSs. Simulation results demonstrate that the proposed greedy heuristic achieves a near-optimal spectrum sharing ratio with a performance gap of only 2.5% compared to an optimization solver, while yielding a 174% improvement in average system throughput compared with a full spectrum sharing scheme.