MBC-SS: A multi-band cooperative sidelink scheme for NR V2X networks

Vehicle-to-everything (V2X) sidelink (SL) communication at mmWave frequency is envisioned to satisfy the exchange of massive sensor data among vehicles. However, directional deafness due to inherent highly directional transmissions results in transmission collisions. Moreover, the high mobility of vehicles incurs significant beam training overhead for beam alignment and tracking. These issues cause performance degradation and pose challenges to SL scheme design. In this paper, we propose a multi-band cooperative SL scheme (MBC-SS) with the concurrent support of resource scheduling and beamforming, which offloads partial mmWave control signals to sub-6 GHz control channels and exploits spatial correlations between multiple frequencies. To enable such multi-band cooperation, centralized and distributed modes are developed for in-coverage and out-of-coverage deployments, respectively, whose advantages are twofold. First, centralized scheduling or receiver-side directional sensing in certain directions is adopted to avoid potential collisions during resource selection phase. Second, we take into account the spatial congruence and temporal dependence of channels to adaptively design training beams and select alignment beams. In addition, the performances of the proposed protocol are investigated theoretically and verified by simulations. Compared with the existing sub-6 GHz assisted scheme, the proposed distributed MBC-SS has an improvement of transmission reliability by 15% and throughput by 12.5% in highly dense scenarios. Meanwhile, lower delay and training overhead are achieved.