Inter-Network Interference Coordination Using Protected Band in Co-existing Networks with HAPS and Terrestrial BSs

This paper proposes an internetwork interference coordination method using protected bands in the downlink of a network where high altitude platform station (HAPS) and terrestrial base stations (TBSs) coexist. When HAPS and TBS share the same transmission band, interference between them degrades the throughput for users, especially at cell edges. When the overall system bandwidth is divided into two non-overlapping bands, where HAPS and TBS use each of these bands, internetwork interference is avoided. However, this reduces the transmission bandwidth HAPS and TBS use, degrading the throughput of cell-interior users. To address this problem, the proposed method divides the overall system band into three parts. The first is a shared band used by both HAPS and TBS, and the other two are protected bands prepared exclusively for HAPS and TBS. By lowering the transmission power at the protected band of non-protected base stations, internetwork interference at the protected band of the target base station is mitigated while avoiding bandwidth loss in the conventional methods. We quantitatively demonstrate the improvement in system throughput achieved by the proposed method through computer simulations.