Simultaneous Information and Control Signalling Protocol for RIS-Empowered Wireless Systems

TL;DR

This paper proposes a novel simultaneous information and control signaling protocol for RIS-empowered wireless systems, enabling real-time operation despite high signaling latency by using NOMA and STAR modes.

Contribution

It introduces the SICS protocol that combines NOMA and STAR modes for RIS control and data transmission, addressing latency issues in RIS signaling.

Findings

SICS enhances robustness against signaling delays.

Optimized RIS reflection and transmission improve data rates.

Superposition coefficients effectively balance control and data signals.

Abstract

Integration of RIS in radio access networks requires signaling between edge units and the RIS microcontroller (MC). Unfortunately, in several practical scenarios, the signaling latency is higher than the communication channel coherence time, which causes outdated signaling at the RIS. To counterbalance this, we introduce a simultaneous information and control signaling (SICS) protocol that enables operation adaptation through wireless control signal transmission. SICS assumes that the MC is equipped with a single antenna that operates at the same frequency as the RIS. RIS operates in simultaneous transmission and reflection (STAR) mode, and the source employs non-orthogonal multiple access (NOMA) to superposition the information signal to the control signal. To maximize the achievable user data rate while ensuring the MC's ability to decode the control signal, we formulate and solve the corresponding optimization problem that returns RIS's reflection and transmission coefficients as well as the superposition coefficients of the NOMA scheme. Our results reveal the robustness of the SICS approach.