Single-RF Multi-User Communication Through Reconfigurable Intelligent Surfaces: An Information-Theoretic Analysis

TL;DR

This paper explores a novel multi-user communication system using a single reconfigurable intelligent surface (RIS) that simultaneously enhances active transmission and enables passive encoding, providing new insights into capacity trade-offs.

Contribution

It introduces a dual-purpose RIS system with both active and passive encoders and characterizes its capacity region through an information-theoretic analysis.

Findings

Capacity region characterized for the dual-encoder RIS system

Trade-offs between active and passive encoding rates analyzed

Insights provided for high- and low-power regimes

Abstract

Reconfigurable intelligent surfaces (RISs) are typically used in multi-user systems to mitigate interference among active transmitters. In contrast, this paper studies a setting with a conventional active encoder as well as a passive encoder that modulates the reflection pattern of the RIS. The RIS hence serves the dual purpose of improving the rate of the active encoder and of enabling communication from the second encoder. The capacity region is characterized, and information-theoretic insights regarding the trade-offs between the rates of the two encoders are derived by focusing on the high- and low-power regimes.