C-RAN (Also CRAN) stands for Centralized RAN or Cloud RAN. In fact, I have seen the industry uses these terms interchangeably.
Option 1
In C-RAN (Cloud RAN) the BBU moves to a centralized location and the cell site only has the antenna and the Radio Unit (RU). This centralization of BBU functionality (also called BBU pool) results in the name centralized RAN or C-RAN.
This results in a new interface called fronthaul, which is between the RRU and BBU pool.
The benefits of C-RAN includes CAPEX and OPEX reduction as deployment and maintenance cost per cell site are reduced because of BBUs centralization.
In addition, it improves spectral efficiency and reduces inter channel interferences, as centralized BBUs can share the resources dynamically among the multiple RRUs. The inter-channel interference is eased because of the joint scheduling and processing.
Option 2: C-RAN with BBU Split
In addition, a second option of the centralized RAN architecture has a further split in BBUs into Distributed Unit (DU) and CU. Here, CU is further towards the core network resulting in a new interface called midhaul.
