build networks that connect the mobile base station to the rest of the Internet. So, the next section deals with the organizations that define standards for the radio access network. 4.6 Radio Access Network 5G networks need to address a wide range of use cases and therefore must be based on a flexible architecture that can adapt to multiple deployment scenarios. Traditionally, the radio access network (RAN) consisted of base stations, radios, and antennas. This equipment normally consisted of ded- icated hardware or proprietary appliances from a radio vendor. There are significant changes now occurring to this model in the RAN, of which the two most important are virtualization and centralization. One change is that some functions in the base station (for example, radio baseband processing) can be virtualized and deployed on the commercial off-the-shelf (COTS) hardware. This is moving the RAN away from the hardware appliance toward a (increasingly open) software model. RAN soft- ware virtualization also allows operators and vendors to build new feature sets to address various industry use cases, including IoT, industrial automation, and SO forth. The second evolution is to move some of the radio processing to a more centralized site instead of it all being hosted out at the cell site. This has advantages for allowing low-latency coordination between neighboring cell sites and reduces the footprint of equipment and infrastructure needed at remote cell sites. The radio components remaining at the cell site are connected to the centralized components via a network-what is now called the front-haul network. Because of latency requirements in radio processing, this front-haul network is not widely spread; typically it is restricted to a radius of up to 20 km. The centralized sites tend to be more like a mini- datacenter and are increasingly operated using cloud-type techniques. To address any ultra-low- latency use cases (autonomous vehicles, for example), application infrastructure can be deployed closer to the end 