Beamforming Design and Performance Analysis for Satellite and UAV Integrated Networks in IoRT Applications

Satellite and unmanned aerial vehicle (UAV) integrated networks (SUINs) are considered as a promising method to offer various Internet of Remote Things (IoRT) applications. In this article, we investigate the downlink transmission SUINs where satellite-to-UAV link uses free-space optical (FSO) technology with an equal gain combining (EGC) scheme while links from UAV IoRT devices exploit radio frequency (RF) space-division multiple access (SDMA) technique. Specifically, considering that only statistical channel state information (CSI) is available, first formulate optimization problem maximize ergodic sum rate (ESR) system, which constrained by total transmit power budget devices’ requirements. Then, beamforming (BF) based on alternating direction multipliers (ADMM) proposed solve nonconvex problem. Furthermore, zero-forcing (ZF)-based suboptimal approach also presented reduce implementation complexity. Finally, assuming FSO RF subject Gamma–Gamma fading Nakagami- $m$ fading, respectively, derive closed-form ESR expressions for network BF schemes. Simulation results provided confirm accuracy theoretical analysis. Moreover, it revealed our EGC communication schemes can both achieve better performance than existing works.