Successive Decode-and-Forward Relaying with Reconfigurable Intelligent Surfaces

TL;DR

This paper introduces a RIS-enhanced successive relaying network that suppresses inter-relay interference and boosts signal quality, using optimization techniques to improve achievable rates with practical implementation considerations.

Contribution

It proposes a novel RIS-assisted SR network with joint phase-shift optimization, offering a low-complexity solution for real-time deployment and demonstrating significant performance gains.

Findings

RISs significantly improve achievable rates in SR networks

PSO-based optimization achieves near-optimal performance

Small RISs provide substantial interference suppression

Abstract

The key advantage of successive relaying (SR) networks is their ability to mimic the full-duplex (FD) operation with half-duplex (HD) relays. However, the main challenge that comes with such schemes is the associated inter-relay interference (IRI). In this work, we propose a reconfigurable intelligent surface (RIS)-enhanced SR network, where one RIS is deployed near each of the two relay nodes to provide spatial suppression of IRI, and to maximize the gain of desired signals. The resultant max-min optimization problem with joint phase-shift design for both RISs is first tackled via the semidefinite programming (SDP) approach. Then, a lower-complexity solution suitable for real-time implementation is proposed based on particle swarm optimization (PSO). Numerical results demonstrate that even relatively small RISs can provide significant gains in achievable rates of SR networks, and the proposed PSO scheme can achieve a near optimal performance.