Quantum Computing Based Optimization for Intelligent Reflecting Surface (IRS)-Aided Cell-Free Network

Intelligent reflecting surface (IRS) enables the control of propagation characteristics and is attracting considerable attention as a technology to improve energy utilization efficiency in 6th generation mobile communication systems. As cell-free networks with multiple distributed base stations (BSs) can communicate in a coordinated manner, they are being actively researched as a new network architecture to resolve the problem of inter-cell interference in conventional cellular networks. The introduction of the IRS into the cell-free network can avoid shadowing at a lower cost with less power consumption. Thus, in this study, we considered the case of communication with user equipment (UE) in a shadowing environment using IRS in a cell-free network that contained distributed BSs with a single antenna. Moreover, the selection of multiple access methods was derived according to the numbers of BSs, IRSs, and UEs. In addition, we proposed a quadratic unconstrained binary optimization formulation to optimize the IRS reflection coefficient using quantum computing. The simulation results verified that the application of the proposed method resulted in a more efficient communication. Thus, this study clarifies that the optimum control method in every communication environment and aims to act as a stepping stone to optimize the entire cell-free system.

Automated summary

Intelligent reflecting surface (IRS) is a technology that controls propagation characteristics and is being widely studied to improve energy efficiency in 6th generation mobile communication systems. In cell-free networks, which consist of multiple distributed base stations (BSs), IRS is introduced to effectively manage inter-cell interference at a lower cost and power consumption. This study investigates the use of IRS in a shadowing environment of a cell-free network with distributed BSs and single antenna, and proposes a quadratic unconstrained binary optimization formulation to optimize the IRS reflection coefficient using quantum computing. Simulation results demonstrate that the proposed method significantly improves communication efficiency. This study provides insights into the optimal control methods for different communication environments and contributes to the optimization of the entire cell-free system.