Spectral-Efficient Network Design for High-Altitude Platform Station Networks With Mixed RF/FSO System

Integrating terrestrial networks with burgeoning high-altitude platform stations (HAPSs) will be a disruptive challenge for beyond-5G systems provisioning large-scale three-dimensional connectivity. Here, we study the problem of forwarding packets between terminals and backhaul through multi-HAPS relaying. Considering limited wireless backhaul, which is practical constraint HAPS relaying, dual-hop mixed radiofrequency/free-space optical (RF/FSO) are investigated, where backhaul-to-relay relay-to-user communications employ FSO RF links, respectively. To maximize end-to-end network throughput, including downlink uplink rate, formulate optimization variables; association aerial terminals, transmit power, deployment multiple HAPSs, We tackle this using an iterative algorithm proposed surrogate functions to efficiently obtain locally optimal solution. Simulation results corroborate that our method achieves up 11.3% spectral efficiency compared conventional heuristic method. Furthermore, answer three questions; 1) what requirements are, 2) how number HAPSs impact network, 3) if certain user terminal has particular demand on data rate.