Rate Splitting Multiple Access in V2X

Abstract

This paper investigates the integration of rate-splitting multiple access (RSMA) into cellular vehicle-to-everything (C-V2X) networks to enhance resource allocation and interference management in decentralized, ad-hoc vehicular communication environments. C-V2X facilitates communication among vehicles, infrastructure, and pedestrians, and traditionally relies on orthogonal frequency division multiple access (OFDMA). However, OFDMA's rigidity limits its effectiveness under dynamic interference and imperfect channel state information (CSI) conditions typical of vehicular networks. RSMA, which blends features of spatial division multiple access (SDMA) and non-orthogonal multiple access (NOMA), provides a more adaptive framework by splitting messages into common and private parts, thereby improving spectral efficiency and interference handling. To assess RSMA's applicability, the LTEV2Vsim simulator was extended to include RSMA functionality, incorporating features such as reputation-based grouping, group-wise resource synchronization, and simplified beamforming. A dynamic grouping algorithm selects high-reputation vehicles as transmission leaders to form multi-vehicle groups of varying sizes for RSMA-based transmission. For interference modeling, self-interference is excluded from SINR calculations, and beamforming-based inter-vehicle interference is approximated. Simulation results reveal that RSMA outperforms OFDMA in terms of spectral efficiency and adaptability, particularly under conditions of incomplete CSI and varying interference. The findings confirm RSMA's suitability for complex and fast-changing vehicular environments, indicating its potential as a robust multiple access scheme for future C-V2X deployments.