Sum-Rate Maximization in Active RIS-Assisted Multi-Antenna WPCN

TL;DR

This paper introduces an active RIS-assisted hybrid relaying scheme for multi-antenna WPCNs, optimizing sum-rate through joint RIS, beamforming, and resource allocation, demonstrating significant performance gains over passive schemes.

Contribution

It proposes a novel active RIS-enabled hybrid relaying scheme with joint optimization techniques for sum-rate maximization in multi-antenna WPCNs, including an efficient solution algorithm.

Findings

Achieves up to 17.78% performance gain over single-antenna schemes.

Attains over 400% improvement compared to passive RIS schemes.

Validates the effectiveness of the proposed optimization algorithm.

Abstract

In this paper, we propose an active reconfigurable intelligent surface (RIS) enabled hybrid relaying scheme for a multi-antenna wireless powered communication network (WPCN), where the active RIS is employed to assist both wireless energy transfer (WET) from the power station (PS) to energy-constrained users and wireless information transmission (WIT) from users to the receiving station (RS). For further performance enhancement, we propose to employ both transmit beamforming at the PS and receive beamforming at the RS. We formulate a sum-rate maximization problem by jointly optimizing the RIS phase shifts and amplitude reflection coefficients for both the WET and the WIT, transmit and receive beamforming vectors, and network resource allocation. To solve this non-convex problem, we propose an efficient alternating optimization algorithm with linear minimum mean squared error criterion, semi-definite relaxation (SDR) and successive convex approximation techniques. Specifically, the tightness of applying the SDR is proved. Simulation results demonstrate that our proposed scheme with 10 reflecting elements (REs) and 4 antennas can achieve 17.78% and 415.48% performance gains compared to the single-antenna scheme with 10 REs and passive RIS scheme with 100 REs, respectively.