Random Access Protocol with Channel Oracle Enabled by a Reconfigurable Intelligent Surface

TL;DR

This paper introduces a novel RIS-assisted random access protocol that leverages a channel oracle to improve throughput in wireless systems, achieving about 60% higher performance than traditional methods without explicit channel estimation.

Contribution

It proposes a new MAC layer protocol integrating RIS control with a channel oracle to enhance random access efficiency without channel estimation.

Findings

Increases throughput by approximately 60% over S-ALOHA.

Utilizes RIS configurations to favor user transmissions dynamically.

Avoids explicit channel estimation through the channel oracle.

Abstract

The widespread adoption of Reconfigurable Intelligent Surfaces (RISs) in future practical wireless systems is critically dependent on the integration of the RIS into higher-layer protocols beyond the physical (PHY) one, an issue that has received minimal attention in the research literature. In light of this, we consider a classical random access (RA) problem, where uncoordinated users' equipment (UEs) transmit sporadically to an access point (AP). Differently from previous works, we ponder how a RIS can be integrated into the design of new medium access control (MAC) layer protocols to solve such a problem. We consider that the AP is able to control a RIS to change how its reflective elements are configured, namely, the RIS configurations. Thus, the RIS can be opportunistically controlled to favor the transmission of some of the UEs without the need to explicitly perform channel estimation (CHEST). We embrace this observation and propose a RIS-assisted RA protocol comprised of two modules: Channel Oracle and Access. During channel oracle, the UEs learn how the RIS configurations affect their channel conditions. During the access, the UEs tailor their access policies using the channel oracle knowledge. Our proposed RIS-assisted protocol is able to increase the expected throughput by approximately 60% in comparison to the slotted ALOHA (S-ALOHA) protocol.