Joint Optimization of IRS Deployment and Passive Beamforming to Enhance the Received Power

TL;DR

This paper proposes a joint optimization framework for IRS deployment and passive beamforming to significantly enhance received power in IRS-assisted wireless communication systems, demonstrating a 37% power gain over benchmarks.

Contribution

It introduces a novel joint optimization method for IRS location and phase shifts, extending existing models to multi-ray reflection scenarios for improved communication efficiency.

Findings

Achieved up to 37% increase in received power with joint optimization.

Derived a comprehensive expression for received power considering physical and reflection factors.

Extended the reflection model from single to multi-ray in 3D space.

Abstract

Intelligent reflecting surface (IRS) has recently emerged as a promising technology for beyond fifth-generation (B5G) and 6G networks conceived from metamaterials that smartly tunes the signal reflections via a large number of low-cost passive reflecting elements. However, the IRS-assisted communication model and the optimization of available resources needs to be improved further for more efficient communications. This paper investigates the enhancement of received power at the user end in an IRS assisted wireless communication by jointly optimizing the phase shifts at the IRS elements and its location. Employing the conventional Friss transmission model, the relationship between the transmitted power and reflected power is established. The expression of received power incorporates the free space loss, reflection loss factor, physical dimension of the IRS panel, and radiation pattern of the transmit signal. Also, the expression of reflection coefficient of IRS panel is obtained by exploiting the existing data of radar communications. Initially exploring a single IRS element within a two-ray reflection model, we extend it to a more complex multi-ray reflection model with multiple IRS elements in 3D Cartesian space. The received power expression is derived in a more tractable form, then, it is maximized by jointly optimizing the underlying underlying variables, the IRS location and the phase shifts. To realize the joint optimization of underlying variables, first, the phase shifts of the IRS elements are optimized to achieve constructive interference of received signal components at the user. Subsequently, the location of the IRS is optimized at the obtained optimal phase shifts. Numerical insights and performance comparison reveal that joint optimization leads to a substantial 37% enhancement in received power compared to the closest competitive benchmark scheme.