A dual-polarized RIS-assisted spatial modulation architecture for robust vehicular communications in urban environments

With Vehicle-to-Vehicle (V2V) communication being one of the enabling elements for intelligent transportation systems and autonomous driving, it enables a reliable one-to-one exchange of safety-related information, including vehicle speed, inter-vehicular distance, braking systems, and the surrounding roadway environment. The highly dynamic nature of vehicular environments, combined with stringent reliability, latency, and energy-consumption requirements, makes it natural to adopt communication architectures that are both spectrally and hardware- and power-efficient. In this context, the current paper explores an intelligent surface (RIS) aid V2V communication system that makes use of a suggested dual-polarized spatial modulation (DPSM) scheme employing one active RF chain per symbol interval over four physical antennas. The suggested architecture makes use of spatial, polarization, and RIS-generated degrees of freedom to augment the adaptability of linkages with significantly lower RF hardware complexity and power usage. Detailed system-level simulations are conducted in realistic conditions, utilizing 3GPP V2V/V2X fading channel models that incorporate vehicle mobility and urban propagation conditions. Major performance indicators, such as received signal strength indicator (RSSI), reference signal received power (RSRP), reference signal received quality (RSRQ), bit error rate (BER), and signal-to-noise ratio (SNR), as well as energy efficiency, are strictly measured and compared with conventional full-MIMO performance. Simulation results demonstrate that the RIS-assisted single-active-RF-chain DPSM scheme can achieve significant energy efficiency gains while maintaining competitive BER performance across a wide SNR range. Where, the transmitter uses physical dual-polarized antennas which provide 8 logical spatial-modulation ports, i.e.,4 antennas× 2 polarizations, but only one RF chain and one logical port are active in each symbol interval. These enhancements in RSSI, RSRP and RSRQ highlight the ability of RIS to provide signal shaping and polarization diversity to reduce the harsh fading and blockage characteristics of the V2V operating environment in the urban environment. Although the full-MIMO system exhibits better BER performance due to its increased spatial diversity, the proposed DPSM architecture offers a more advantageous trade-off between performance, complexity, and energy. These results support the use of the RIS-supported DPSM architecture as a highly suitable and convenient design for next-generation V2V communications, particularly on systems with power- and cost-limited vehicle platforms.