Performance Enhancement of C-V2X Mode-3 with Smart Handover and Wide Area DENM Propagation

To enhance safety in intelligent transportation systems (ITS), seamless exchange of cooperative awareness messages (CAMs) and prompt wide-area broadcasting of decentralized environmental notification messages (DENMs) among neighbor vehicles are essential. This paper proposes an enhanced Cellular vehicles-to-everything (C-V2X) mode-3 networking with i) scalable overlapped eNodeBs (eNBs) with orthogonal radio frequency (RF) resource management with minimized RF interference, ii) smart handover across overlapped eNBs to minimize the signaling overhead, and iii) prompt wide-area propagation of DENM across neighbor eNBs with collaborations of eNBs. In the proposed scheme, scalable overlapped eNBs are configured with 3 ~ 4 orthogonal sub-channels supporting up to 400 vehicles per eNB. 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 eNBs guarantees seamless CAM deliveries even at the boundaries of eNBs and reduces delay by avoiding the re-registration process of vehicles at boundary of each eNB. The proposed system also supports efficient delivery of emergency warnings which are collected by vehicles or public warning system (PWS) and delivered as DENMs through system information block (SIB). The DENMs are promptly propagated to neighbor eNBs and broadcasted based on collaborations of eNBs. The operations of the proposed scheme have been implemented in NS-3 simulation and measured performance results are analyzed in detail. The CAM delivery rates are more than 99.8 percent in highly congested metropolitan areas, and the prompt propagation of DENMs across multiple eNBs is provided within 100 msec.