Shaping mmWave Wireless Channel via Multi-Beam Design using Reconfigurable Intelligent Surfaces

TL;DR

This paper introduces a novel multi-beam RIS design for mmWave channels, enabling enhanced coverage by shaping reflected beams with optimized gain and sharp edges, validated through theoretical and numerical analysis.

Contribution

It presents a new multi-beamforming approach for RIS with a closed-form solution, improving coverage and beam shaping in mmWave communications.

Findings

Multi-beam RIS achieves disjoint beam lobes with optimized gain.

The proposed design reduces power leakage outside desired coverage.

Numerical analysis confirms the effectiveness of the multi-beamforming approach.

Abstract

Millimeter-wave (mmWave) communications is considered as a key enabler towards the realization of next-generation wireless networks, due to the abundance of available spectrum at mmWave frequencies. However, mmWave suffers from high free-space path-loss and poor scattering resulting in mostly line-of-sight (LoS) channels which result in a lack of coverage. Reconfigurable intelligent surfaces (RIS), as a new paradigm, have the potential to fill the coverage holes by shaping the wireless channel. In this paper, we propose a novel approach for designing RIS with elements arranged in a uniform planar array (UPA) structure. In what we refer to as multi-beamforming, We propose and design RIS such that the reflected beam comprises multiple disjoint lobes. Moreover, the beams have optimized gain within the desired angular coverage with fairly sharp edges avoiding power leakage to other regions. We provide a closed-form low-complexity solution for the multi-beamforming design. We confirm our theoretical results by numerical analysis.