Blind Beamforming for Coverage Enhancement with Intelligent Reflecting Surface

TL;DR

This paper introduces a blind beamforming method for IRS that enhances coverage without requiring channel state information, achieving near-optimal SNR improvements demonstrated through simulations and real-world experiments.

Contribution

It proposes a novel blind beamforming strategy relying solely on received power data, eliminating the need for channel state information and geographic models.

Findings

Guarantees minimum SNR of Ω(N^2/U) with N reflective elements and U positions.

Achieves near upper bound of SNR improvement compared to existing methods.

Field test shows 18.22 dB SNR boost in real-world scenario.

Abstract

Conventional policy for configuring an intelligent reflecting surface (IRS) typically requires channel state information (CSI), thus incurring substantial overhead costs and facing incompatibility with the current network protocols. This paper proposes a blind beamforming strategy in the absence of CSI, aiming to boost the minimum signal-to-noise ratio (SNR) among all the receiver positions, namely the coverage enhancement. Although some existing works already consider the IRS-assisted coverage enhancement without CSI, they assume certain position-channel models through which the channels can be recovered from the geographic locations. In contrast, our approach solely relies on the received signal power data, not assuming any position-channel model. We examine the achievability and converse of the proposed blind beamforming method. If the IRS has $N$ reflective elements and there are $U$ receiver positions, then our method guarantees the minimum SNR of $\Omega(N^2/U)$ -- which is fairly close to the upper bound $O(N+N^2\sqrt{\ln (NU)}/\sqrt[4]{U})$. Aside from the simulation results, we justify the practical use of blind beamforming in a field test at 2.6 GHz. According to the real-world experiment, the proposed blind beamforming method boosts the minimum SNR across seven random positions in a conference room by 18.22 dB, while the position-based method yields a boost of 12.08 dB.