 this site has a dark fiber car- rying CPRI that runs from the centralized location to each cell site that is homed on that particular centralized site. There are several advantages to this configuration. The centralized pool of BBUs can provide reduced lease and operations costs. In some configurations BBU capacity can be configured to be shared across multiple cell sites, reducing capital costs. The BBUs can also be easily intercon- nected with high-speed and low latency links, which can facilitate some advanced features that help improve the performance of the RAN network by coordinating between the different cell sites. The Local To Core Backhaul Network Cell Site FIGURE 11.13 Block diagram of the dRAN architecture. Fronthaul Backhaul Cell Site Central Site FIGURE 11.14 Block diagram of the cRAN architecture. Network Access main disadvantage of this architecture is the need for dark fiber transport from the central site to each cell site, carrying the inefficient CPRI protocol. In many situations, this transport may not be avail- able or cost effective, when compared with using Ethernet transport to connect with the cell sites. The cRAN architecture provides more opportunities for applying SDN and NFV techniques. The central baseband pooling site consists of a collection of interconnected BBUs, with each BBU containing specialized DSP hardware and firmware, as well as general purpose processing and networking hardware and software. This provides an opportunity to implement the functions at the central baseband pooling site by disaggregating the functions of the BBU, and using the general architectural approach shown in Figure 11.2. In this architecture, the functions normally executed by the specialized DSP hardware are virtualized and executed on the specialized hardware compo- nent of the extended AIC architecture, and the other functions are executed in the general purpose servers and networking components. Because of the distance and cost restrictions of the CPRI link, the cRAN architecture can only be ef