Enhanced C-V2X Mode-3 with Smart Handover and Wide-area Propagation of Emergency Warnings

Seamless exchange of cooperative awareness messages (CAMs) and prompt wide-area propagation of emergency warnings among neighbor vehicles are essential to improve safety of vehicles in intelligent transportation systems (ITS). This paper proposes enhanced C-V2X mode-3 operations with i) efficient multiple overlapped cells with orthogonal RF resource managements, ii) smart handover across overlapped cells to minimize the signaling overhead, and iii) prompt wide-area propagation of emergency warnings across multiple cells with collaborations of eNodeBs(eNBs). In the proposed scheme, scalable overlapped cells are configured with 3 ∼ 4 orthogonal sub-channels for up to 400 vehicles per eNodeB. The eNB continuously monitors the CAM broadcasting by vehicles and assigns resources to the vehicles with balanced RF channel usages to mitigate half-duplex problem. The smart handover across overlapped cells guarantees seamless CAM deliveries even at the boundaries of cells and reduces delay by avoiding the re-registration process of vehicles at boundary of each cell. It also provides prompt propagation of wide-area emergency warnings based on collaborations of eNBs. The operations of the proposed scheme have been implemented and analyzed with NS-3 simulation, and measured results of CAM delivery rates are more than 99.4 percent in highly congested metropolitan areas. Also, the prompt propagation of emergency warnings across multiple cells are provided within 200 msec.