Cloud-RAN (C-RAN)

In Classical RAN, The RRH (Remote Radio Head) & BBU (BaseBand Unit) are located in the same tower or building. The RRH is the Outdoor unit and the BBU is the Indoor unit. Both are connected using Ethernet or Fiber Cabling. A new Innovation is designed to enhance the performance by decentralizing the RRH from BBU. This is defined as the distributed radio access network (Cloud-RAN or C-RAN) architecture. This includes Remote Radio Heads (RRHs) connected to the baseband unit (BBU) using CPRI (Common Public Radio Interface) or OBSAI (Open Base Station Architecture Initiative) interfaces. The RRHs include the radio, the associated amplification/filtering, and the antenna. The BBU is implemented separately and performs the centralized signal processing functionality of the RAN. The decentralized BBU enables agility, faster service delivery, cost savings, and improved coordination of radio capabilities across a set of RRHs. In addition, a number of BBUs can be aggregated to form a Centralized Baseband Unit (C-BBU) as depicted in figure 1, showing the migration from existing RAN architecture to the C-RAN evolution. The C-BBU is a new RAN architecture that is a two-dimensional cluster of RRHs and BBUs 

C-RAN is increasingly relevant in LTE-Advanced where advanced interference control techniques such as eICIC (enhanced Inter-Cell Interference Coordination) will benefit from the parallelism and increased processing power at the centralized BBU. In addition, other LTE-Advanced features such as carrier aggregation and CoMP (Coordinated Multipoint) will leverage the operational efficiencies of resource sharing at the centralized processing unit.