Energy Efficiency Optimization of Finite Block Length STAR-RIS-aided MU-MIMO Broadcast Channels

TL;DR

This paper proposes energy efficiency optimization for MU-MIMO broadcast channels aided by STAR-RIS, demonstrating significant EE gains especially under strict latency and reliability constraints at finite block lengths.

Contribution

It introduces a novel energy efficiency maximization framework for STAR-RIS-assisted MU-MIMO channels operating at finite block lengths, highlighting the benefits of STAR-RIS in energy savings.

Findings

STAR-RIS substantially enhances energy efficiency.

Energy gains increase with stricter latency and reliability.

Optimal design depends on codeword length and error rate constraints.

Abstract

Energy-efficient designs are proposed for multi-user (MU) multiple-input multiple-output (MIMO) broadcast channels (BC), assisted by simultaneously transmitting and reflecting (STAR) reconfigurable intelligent surfaces (RIS) operating at finite block length (FBL). In particular, we maximize the sum energy efficiency (EE), showing that STAR-RIS can substantially enhance it. Our findings demonstrate that the gains of employing STAR-RIS increase when the codeword length and the maximum tolerable bit error rate decrease, meaning that a STAR-RIS is more energy efficient in a system with more stringent latency and reliability requirements.