System Design for Maximizing Rate in Vehicle Networking with Reconfigurable Intelligent Surface (RIS) Assistance

In this paper, we propose an optimization algorithm for RIS-assisted multiple-input single-output vehicle communication systems, Given a vehicle-to-vehicle user signal to interference plus noise ratio requirement, we optimize the transmit beamforming vector and phase shift matrix of RIS to obtain the maximum transmission rate of vehicle to infrastructure user. To deal with the coupled variables in the optimization problem, the alternate iterative algorithm is exploited to divide the original optimization problem into two sub-problems, each with a single variable. Moreover, the first-order Taylor expansion and the semidefinite relaxation methods are used to transform the nonconvex sub-problems into convex optimization problems. The simulation results are presented to validate the superiority of the proposed method compared to the benchmark schemes. Additionally, the simulation results also reveal that there exits an optimal vehicle speed under different path loss exponents so as to achieve the maximum transmission rate if the RIS is used by our proposed beamforming method.