th emphasis on the autonomous mode due to its lower latency. Further enhancements to accommodate high-speed/high-Doppler, high-vehicle density, improved synchronization, and decreased message transfer latency have been studied. This mode is suitable for proximal direct com- munications over short distances and for V2V safety applications that require low latency; for example, advanced driver-assistance systems or situational awareness. This mode can work in and out-of-network coverage (see Fig. 7.2). Network-based communication uses the LTE Uu interface between the vehicle (i.e., the UE) and the eNBs. The UEs send unicast messages via the eNB to an application server, which in turn re-broadcasts them via evolved multimedia broadcast multicast service (eMBMS) for all UEs in the relevant geographical area. This mode uses the existing LTE radio access and is suitable for latency-tolerant use cases (e.g., situational awareness, mobil- ity services). It is possible to deploy the network-based mode in an operator licensed spec- trum, while the direct PC5-based mode can be deployed in unlicensed spectrum. LTE uses unicast and broadcast bearers for data transmission. Broadcast is applicable, if the mobile operator has deployed eMBMS. LTE can complement the short-range communica- tion path for V2X provided by other technologies (e.g., DSRC/IEEE 802.11p). This type of broadcast transmission can potentially cover more vehicles in network coverage because the network can control the broadcast range, which is more suitable for the V2I/V2N type of services. Mobile operators can provide additional value-added services to subscribed drivers including traffic jams/blocked roads further ahead, real-time map/3D building/landmarks, World Radiocommunication Conference 2019 (WRC-19) https://www.itu.int/en/ITU-R/conferences/wrc/2019 Vehicle-to-Everything (V2X) Communications 803 Application server Application Application server server S/P-GW V2X Control S/P-GW function V2X Control V2X Control function function (Pedestrian) Application 