MISO Wireless Communication Systems via Intelligent Reflecting Surfaces

TL;DR

This paper investigates the joint optimization of beamforming and IRS phase shifts in IRS-assisted MISO wireless systems, proposing algorithms that improve spectral efficiency and reduce computational complexity, with large-scale IRS deployment outperforming antenna array expansion.

Contribution

It introduces two novel algorithms for joint beamforming and IRS phase shift optimization, enhancing spectral efficiency and computational efficiency in IRS-assisted MISO systems.

Findings

Proposed algorithms outperform existing methods in spectral efficiency.

Large-scale IRS deployment is more effective than increasing AP antennas.

Simulation confirms improved energy and spectral efficiency with IRS.

Abstract

Intelligent reflecting surfaces (IRSs) have received considerable attention from the wireless communications research community recently. In particular, as low-cost passive devices, IRSs enable the control of the wireless propagation environment, which is not possible in conventional wireless networks. To take full advantage of such IRS-assisted communication systems, both the beamformer at the access point (AP) and the phase shifts at the IRS need to be optimally designed. However, thus far, the optimal design is not well understood. In this paper, a point-to-point IRS-assisted multiple-input single-output (MISO) communication system is investigated. The beamformer at the AP and the IRS phase shifts are jointly optimized to maximize the spectral efficiency. Two efficient algorithms exploiting fixed point iteration and manifold optimization techniques, respectively, are developed for solving the resulting non-convex optimization problem. The proposed algorithms not only achieve a higher spectral efficiency but also lead to a lower computational complexity than the state-of-the-art approach. Simulation results reveal that deploying large-scale IRSs in wireless systems is more efficient than increasing the antenna array size at the AP for enhancing both the spectral and the energy efficiency.