C-RAN is emerging as an important platform for next-generation radio access networks (RANs). Standing for both centralized RAN and cloud RAN, the C-RAN concept is based around the idea of a centralized baseband processing pool serving n number of distributed radio access nodes.
Centralized baseband processing is primarily useful because it enables better (faster, more granular) coordination of radio resources across distributed access nodes than a classic macro cell architecture. In systems such as LTE and LTE Advanced (LTE-A), where coordinated processing is essential to performance improvements, the capability to manage this centrally rather than via an external X2 interface between base stations could generate important performance gains.
Arguably, the hyper-densification of RAN will, in time, require some form centralized, collaborative processing to reduce and manage inter-cell interference between neighboring cells and across access layers in heterogeneous networks. Looking further ahead toward 5G and to the concept of integrated management of cloud and radio resources, the C-RAN model could become more attractive still.
There are also several secondary benefits to C-RAN. Most notable, from an operator perspective, is reduced opex. With a simpler cell site installation there may be an opportunity to reduce lease costs at the site, for example. And with a centralized server pool there is potential to reduce maintenance and upgrade costs. These are very much second-order benefits, however, and in many markets are not sufficiently useful to justify the complexity of C-RAN. Performance is king.
