allocation, mobility, and interference control for a large number of inter- faces [toward remote radio units (RRUs)] using programmable software layers. The V-RAN architecture benefits from software-defined capacity and scaling limits. It enables selective content caching, which helps to further reduce network deployment and maintenance costs as well as to improve user experience based on its cloud infrastructure. Aggregator Cloud BBU Aggregator Switch Aggregator Cloud RAN architecture with Distributed RAN architecture Cloud RAN architecture with virtualized EPC virtualized BBU and EPC Figure 1.23 Base station architecture evolution and high-level C-RAN architecture [ 5G Network Architecture 59 In a traditional cellular network architecture, each physical base station unit encompasses both baseband and radio processing functions. In C-RAN, the baseband processing for a large number of cells is centralized, resulting in improved performance due to the ability to coordinate among multiple cells, and cost reduction as a result of pooling the shared resources. Small cells, when densely deployed across a large indoor environment, create large areas of overlap between neighboring cells. Inter-cell interference occurs at the cell boundaries. Some enterprise small cells use a central service controller to assist in hand- overs and backhaul aggregation, but it cannot overcome the fact that each cell interferes with its neighbors since some level of interference is inevitable. Creating multiple indepen- dent cells further necessitates frequent handovers for mobile terminals, degrading the user experience and creating the potential for handover failures or constant back-and-forth hand- overs between adjacent cells, a phenomenon known as ping-pong effect. Cell virtualization enables allocation of users' data over the same radio resources but sent to different access nodes for transmission to different users. In general, a C-RAN architecture consists of three main entities: BBU(s), RRH/units, and the transport network or what