A Random Access Protocol for RIS-Aided Wireless Communications

TL;DR

This paper introduces a novel random access protocol for RIS-assisted wireless systems, enabling efficient user access through a set of predefined RIS configurations, balancing success rate and access delay.

Contribution

It proposes a new protocol that uses a finite set of RIS configurations for area coverage, addressing protocol design overlooked in RIS literature.

Findings

Increases average successful access attempts

Improves performance in high load scenarios

Introduces a trade-off between success rate and delay

Abstract

Reconfigurable intelligent surfaces (RISs) are arrays of passive elements that can control the reflection of the incident electromagnetic waves. While RIS are particularly useful to avoid blockages, the protocol aspects for their implementation have been largely overlooked. In this paper, we devise a random access protocol for a RIS-assisted wireless communication setting. Rather than tailoring RIS reflections to meet the positions of users equipment (UEs), our protocol relies on a finite set of RIS configurations designed to cover the area of interest. The protocol is comprised of a downlink training phase followed by an uplink access phase. During these phases, a base station (BS) controls the RIS to sweep over its configurations. The UEs then receive training signals to measure the channel quality with the different RIS configurations and refine their access policies. Numerical results show that our protocol increases the average number of successful access attempts; however, at the expense of increased access delay due to the realization of a training period. Promising results are further observed in scenarios with a high access load.