osed for the infrastructure application. The main Central Processing Unit (CPU) provides an interface to the V2X modem as well as CPU horsepower to translate V2X mes- sages to wide area network interfaces [Ethernet, LTE/5G wireless, or (less likely) Wi-Fi wire- less] as well as to run application stacks needed to interpret and (more importantly) transmit safety-critical messages-the V2X application layer. Challenges with this approach include (1) the V2X communication path and (2) scalability: V2X communication path challenge. As we explained earlier, typical RSU implementations reuse a vehicular V2X modem for V2I communication. Challenges with this implementation include the following: Standards compliance. Whereas a client module is built with a specific use case, market, and lifetime in mind, an RSU may have to adhere to a wider range of standards (say, 802.11p and C-V2X both) as well as future standards enhancements that come with a lifetime of 10 + years in the field. These requirements can be readily supported with a more flexible (e.g., software defined and O-RAN based) implementation as opposed to a hardwired modem implementation. RF performance. The V2X modem is implemented with an RF chain that is optimized for client (UE) use. Besides cost optimization targets that typically imply performance compromises, this also limits fundamental aspects such as antenna gain [antenna path count, multiple-input, multiple-output (MIMO)], RF output power (UE category is limited to 20-23 dBm), and so on. These limitations do not have to apply to an RSU that falls in the base station RF category. Industrialization. Consumer- and industrial-grade components comply to different standards with regards to temperature range, operational lifetime, sensitivity to failure conditions, and SO on. 360 Open Radio Access Network (O-RAN) Systems Architecture and Design Modem performance. In terms of number of communication messages/second, RF channels, RF bandwidth, sectorization topics, and so on, an RSU has widely different perform