tween implementation options will be use case dependent. Vehicle-to-infrastructure (vehicle-to-anything) roadside unit architecture and implementation Introduction Even though safety-critical communication mechanisms targeting automotive have been around for many years (first widely known protocol defined for the purpose being IEEE 802.11p11 inter- est has grown significantly in the last years. New, dedicated, technologies are being developed to give cars the capability to interact directly with each other and with road infrastructure. These interactions are known as of Cooperative Intelligent Transport Systems (C-ITS). Chapter 11 Differentiation by use case 355 FIGURE 11-3 V2Anything communication. C-ITS allows road users to share information that helps to make transportation safer and more efficient. However, to make C-ITS work, roadside infrastructure and vehicle communi- cation need to be both standardized and more broadly implemented. Known as vehicle-to-everything (Fig. 11-3), C-ITS covers multiple communication paths: vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P). C-ITS supports two main application areas: safety-critical applications and additional services. This imposes challenges on appropriate prioritization (safety critical above anything else) and dynamic behavior with high relative speeds (vehicular) between transmitter and receiver(s), for both rural and urban scenarios, considering latency restrictions for safety-related applications. Spectral aspects Most global spectrum dedicated for ITS/vehicle-to-anything (V2X) communications is the 5.9 GHz band (5.850-5.925 GHz), even though there is little harmonization (but a lot of active discussion) of channel allocations within this band (Fig. 11-4). One notable exemption is Japan which allocates 755.5-764.5 and 5770-5850 MHz spec- trum to ITS. RF requirements such as transmit power can be different across regions/standards. 3GPP stipulates an allowed V2X UE maximum output power of ~ 