Cloud radio access networks: Principles, challenges, and technologies

Cloud radio access network is a novel architecture which can address the cost, energy, and bit rate concerns the mobile operators are facing to support explosive growth in mobile data traffic. Unlike a typical RAN, the C-RAN decouples the baseband unit (BBUs) from the radio units by locating the BBUs at the high performance cloud infrastructure. The key insight is that if the network capacity is limited by the interference and its workload is changing over time and space, then centralizing radio processing can dramatically increase the network capacity through joint and coordinated processing and reduce the overall energy consumption by exploiting load variations. This tutorial aims at providing a big picture of C-RAN, a well-balanced state-of-the-art research topics and advances, and the role of C-RAN in 5G systems. It is organized in four technical parts covering principles, challenges, key technologies, and proof-of-concept prototypes and field trials in C-RAN.