Reconfigurable Intelligent Surface Phase Hopping for Ultra-Reliable Communications

TL;DR

This paper proposes a phase hopping scheme for reconfigurable intelligent surfaces that converts slow fading into fast fading, significantly improving ultra-reliable communication performance without needing channel state information.

Contribution

The paper introduces a novel phase hopping method for RISs that enhances reliability without requiring channel state information or additional communication overhead.

Findings

Improved outage performance for small outage probabilities

Effective even with only two phase options

No need for channel state information at transmitter or RIS

Abstract

We introduce a phase hopping scheme for reconfigurable intelligent surfaces (RISs) in which the phases of the individual RIS elements are randomly varied with each transmitted symbol. This effectively converts slow fading into fast fading. We show how this can be leveraged to significantly improve the outage performance especially for small outage probabilities without channel state information (CSI) at the transmitter and RIS. Furthermore, the same result can be accomplished even if only two possible phase values are available. Since we do not require perfect CSI at the transmitter or RIS, the proposed scheme has no additional communication overhead for adjusting the phases. This enables robust ultra-reliable communications with a reduced effort for channel estimation.