On Performance of Integrated Satellite HAPS Ground Communication: Aerial IRS Node vs Terrestrial IRS Node

With an objective of ubiquitous connectivity around the world with enhanced spectral efficiency, intelligent reflecting surfaces (IRS) integrated satellite-terrestrial communications is a topic of research interest specially in infrastructure-deficient terrains. In line with this vision, this paper entails the performance analysis of satellite-terrestrial networks leveraging both aerial and terrestrial IRS nodes, with the support of high altitude platforms (HAPS) over diverse fading channels including shadowed Rician, Rician, and Nakagami-m fading channels. The merits of IRS in enhancing spectral efficiency is analyzed through closed-form expressions of outage probability and ergodic rate. Further, the average symbol error rate analysis for the higher-order quadrature amplitude modulation (QAM) schemes such as hexagonal QAM, rectangular QAM, cross QAM, and square QAM is performed. Practical constraints like antenna gains, path loss, and link fading are considered to characterize the satellite terrestrial links. Finally, a comparison between the HAPs based IRS node and terrestrial IRS nodes is performed and various insights are drawn under various fading scenarios and path loss conditions. Our results demonstrate that aerial IRS nodes offer superior performance in terms of outage probability, ergodic rate, and symbol error rate for higher-order QAM schemes. Additionally, the study reveals that the ergodic rate in aerial IRS systems scales with the number of IRS elements, while terrestrial IRS systems rely on the diversity of the satellite-HAP link.