Doppler Mitigation and Reflection Coefficient Design for Double-IRS-Aided High-Mobility V2V Communications

Intelligent reflecting surface (IRS) has emerged as a revolutionary technology for intelligently reshaping the wireless propagation environment by adaptively adjusting the phase shifts of low-cost passive elements. Prior studies have primarily focused on the single-IRS-aided transmission involving a static basis station (BS) and a high-mobility vehicle. In this paper, we extend this research to a double-IRS-aided high-mobility vehicle-to-vehicle (V2V) communication system, where both the transmitter (TX) and the receiver (RX) experience individual Doppler shifts. Based on the considered scenario, we propose a novel time-varying channel estimation algorithm, where the double-IRS is integrated into the system to enhance the joint channel gain, and employ the basis expansion model (BEM) to predict the non-IRS-reflected channel in Stage 2 of the considered transmission protocol based on the estimated non-IRS-reflected channel obtained in Stage 1, thus obviating the need for channel estimation in Stage 2. Subsequently, we estimate the TX-IRS-RX cascaded channels and dynamically adjust the double-IRS reflection patterns over time to align the non-IRS-reflected channel with the TX-IRS-RX cascaded channels, thereby maximizing the passive beamforming gain of the double-IRS. Simulation results validate the superiority of the proposed scheme over the other benchmark schemes.