Reconfigurable Intelligent Sensing Surface aided Wireless Powered Communication Networks: A Sensing-Then-Reflecting Approach

TL;DR

This paper introduces a reconfigurable intelligent sensing surface (RISS) that enhances wireless powered communication by autonomously estimating user directions and optimizing reflections, reducing overhead and improving energy transfer efficiency.

Contribution

The work proposes a novel RISS that combines sensing and reflecting functions, enabling independent operation from the hybrid access point and improved system performance.

Findings

Outperforms conventional systems by 2.3 dB and 4.7 dB in different Rician scenarios.

Provides a closed-form expression for system performance under DOA errors.

Offers a protocol for autonomous DOA estimation and reflection phase design.

Abstract

This paper presents a reconfigurable intelligent sensing surface (RISS) that combines passive and active elements to achieve simultaneous reflection and direction of arrival (DOA) estimation tasks. By utilizing DOA information from the RISS instead of conventional channel estimation, the pilot overhead is reduced and the RISS becomes independent of the hybrid access point (HAP), enabling efficient operation. Specifically, the RISS autonomously estimates the DOA of uplink signals from single-antenna users and reflects them using the HAP's slowly varying DOA information. During downlink transmission, it updates the HAP's DOA information and designs the reflection phase of energy signals based on the latest user DOA information. The paper includes a comprehensive performance analysis, covering system design, protocol details, receiving performance, and RISS deployment suggestions. We derive a closed-form expression to analyze system performance under DOA errors, and calculate the statistical distribution of user received energy using the moment-matching technique. We provide a recommended transmit power to meet a specified outage probability and energy threshold. Numerical results demonstrate that the proposed system outperforms the conventional counterpart by 2.3 dB and 4.7 dB for Rician factors $\kappa_h=\kappa_G=1$ and $\kappa_h=\kappa_G=10$, respectively.