Energy-Efficient STAR-RIS-aided MU-MIMO System for Next-Generation Green URLLC

Abstract

This paper investigates a novel simultaneous transmission and reflection reconfigurable intelligent surface (STAR-RIS) aided downlink (DL) ultra-reliable low-latency communications (URLLC) to deliver a green URLLC service for next-generation wireless networks. In particular, we focus on the problem of energy-efficient resource allocation design for a phase-shift coupled STAR-RIS-aided multi-user multiple-input-multiple output (MU-MIMO) system with optimal beamforming at the base-station (BS) and STAR-RIS under given requirements on the packet-error probability and latency. Owing to the non-convex and NP-hard nature of the formulated problem, we propose an alternating optimization framework which solves the problems of beamforming design at the BS and STAR-RIS independently in an iterative manner using pricing allocation and successive convex approximation approaches. Simulation results confirm that the STAR-RIS can significantly improve the energy efficiency by 30-40% when compared to conventional reflecting-only RIS while guaranteeing the strict reliability and latency requirements of URLLC.