Decentralized User Association Method to Maximize System-Level Throughput Satisfaction Rate in Co-existing Networks with HAPS and Terrestrial BSs

This paper proposes an autonomous decentralized user association method for the networks where the high-altitude platform station (HAPS) and conventional terrestrial base stations (BSs) are operated in the same coverage area. The throughput satisfaction rate of each user is defined as the ratio of the actual throughput to the target throughput. The purpose of the proposed method is to maximize the system-level throughput satisfaction rate, which is defined as a generalized mean of the throughput satisfaction rates of all users in the system coverage. The proposed method achieves optimal user association by iteratively performing an autonomous decentralized process that does not require complex cooperation among HAPS and terrestrial BSs. Computer simulation results show that the proposed method can increase the system-level throughput satisfaction rate compared to the conventional cell range expansion (CRE) method and that this increase is particularly significant when fairness among users in terms of the throughput satisfaction rate is emphasized.