Energy Efficiency Optimization for Active Simultaneously Transmitting and Reflecting Surface Assisted Satellite in IoT Networks

This paper investigates the maximization of energy efficiency in an active simultaneously transmitting and reflecting reconfigurable intelligent surface (ASTARS) assisted non-orthogonal multiple access (NOMA) satellite Internet of Things (IoT) with finite blocklength (FBL) transmission. The activated IoT devices (AIoTDs) can be divided into activated reflectionregion IoTDs (ARDs) and activated transmission-region IoTDs (ATDs). Considering the massive-access requirements of the AIoTDs, two device pairing strategies, namely strong-ARD poor-ATD pairing (SPP) and strong-ARD strong-ATD pairing (SSP), are proposed to enable energy-efficient transmission. The penalty alternating iterative algorithm (PAIA) is proposed to handle the optimization problem to maximize energy efficiency. Simulation results demonstrate that the ASTARS achieves higher energy efficiency compared to both the passive simultaneously transmitting and reflecting surface (PSTARS) and systems without reconfigurable intelligent surfaces (RIS).