Outage Analysis for a HAPS-Mounted IRS-Assisted Multi-User Communication System

In this paper, we propose a high altitude platform station (HAPS)-mounted intelligent reflecting surface (IRS)assisted multi-user communication system. Due to potential blockage or the fact that the users might be located outside of the coverage of the terrestrial base station (TBS), there might not be a direct service link from the TBS to the users. Hence, with the use of the reflected signals from the HAPS-mounted IRS, the TBS is able to provide services to its associated user equipment (UEs). With this proposed scenario, the coverage area can be substantially increased as the HAPS are usually located in high altitudes. We study the outage performance of the proposed system taking into account the UEs distribution in the service area. We derive an approximate closed-form expression for the outage probability under a Rician-faded TBS-HAPS link and a shadowed Rician-faded HAPS-UEs link. Moreover, we validate our derived expression through Monte Carlo simulations considering the effect of different system parameters on the outage probability. Results show that the proposed system can achieve outage probability in the order of 10^-4 up to a service area diameter of 30 km and in the order of 10^-2 for service areas in the range of 40 km in diameter.