System Level Simulation of HAPS Mobile Communications with Frequency Reuse Schemes

Direct communication between High-Altitude Platform Stations (HAPS) and terminal devices has been shown to utilize frequency bands identical to those used by terrestrial systems. Therefore, when applying the HAPS system in areas that overlap with terrestrial networks, it is crucial to reduce interference between the two systems while maximizing the performance of both HAPS and terrestrial systems. Although a simple solution is to divide the frequency bands for each terrestrial and HAPS system, inter-beam interference within the same HAPS can lead to a decline in spectral efficiency. To address this issue, a frequency reuse scheme is a reliable method to suppress interference. However, in the case of HAPS architecture, the beams for which frequency reuse is applied must be selected according to the geographical features and the configuration of the base stations to minimize inter-system interference with the terrestrial system. In this paper, we evaluate system throughput and inter-beam interference using a system-level simulator designed to replicate actual terrestrial environments. The results demonstrate the effectiveness of the frequency reuse scheme, which simultaneously improves both spectral efficiency and inter-beam interference, even in realistic environments.