Dumb RIS-Assisted Random Beamforming for Energy Efficiency Enhancement of Wireless Communications

TL;DR

This paper introduces a novel RIS-assisted random beamforming scheme with a single-active-antenna structure that enhances energy efficiency in wireless networks without requiring full channel state information.

Contribution

It proposes a new single-active-antenna RIS transmitter and a random beamforming scheme that improves energy efficiency without full CSI, reducing hardware and power costs.

Findings

Significant EE improvement over traditional multi-antenna systems.

Effective RIS phase shift randomization based on user feedback.

Joint optimization of RIS elements and transmit power enhances EE.

Abstract

Energy efficiency (EE) is one of the most important metrics for the beyond fifth generation (B5G) and the future sixth generation (6G) wireless networks. Reconfigurable intelligent surface (RIS) has been widely focused on EE enhancement for wireless networks because it is power-saving, programmable, and easy to be deployed. However, RIS is generally passive and thus difficult to obtain corresponding full channel state information (CSI), which severely impacts the EE enhancement of RIS-assisted wireless communications. To solve this problem, in this paper we propose the new single-active-antenna combined RIS transmitter structure, which can replace traditional multiple antennas to reduce hardware cost and power consumption. Based on the single-active-antenna combined RIS structure, we develop the Dumb RIS-Assisted Random Beamforming (Darb)-based Joint RIS-Elements and Transmit-power optimizAtion (Jeta) scheme, where dumb RIS randomly changes its phase shift according to isotropic distribution only depending on the CSI feedback from users to RIS-assisted transmitter. Then, we jointly design the number of RIS elements and optimize the transmit power to maximize the EE of RIS-assisted wireless communications. Simulation results show that compared with the traditional multi-antenna system, our developed Darb-based-Jeta scheme can significantly increase the EE without the full CSI.