RIS reflection pattern design for vehicular platoon communications in mmWave channels

In this paper, we propose a reflection pattern design scheme for reconfigurable intelligent surface (RIS) assisted vehicular platoon communications in millimeter wave (mmWave) channels. We focus on optimizing the reflection pattern of a RIS that is installed in a roadside unit to maximize the broadcast information rate from the lead vehicle in a platoon to each following member vehicle. We show that this problem can be effectively solved using semidefinite programming. Next, we propose a reflection pattern design scheme for the RIS that maximizes its reflection gain by exploiting the angle of departure, angle of arrival, and path loss information between each vehicle and the RIS in mmWave channels. Finally, we present numerical results that demonstrate the effectiveness of our proposed reflection pattern design scheme.