  Cloud Radio Access Network (C-RAN) refers to the virtualization of base
station functionalities by means of cloud computing. This results in a novel
cellular architecture in which low-cost wireless access points, known as radio
units (RUs) or remote radio heads (RRHs), are centrally managed by a
reconfigurable centralized "cloud", or central, unit (CU). C-RAN allows
operators to reduce the capital and operating expenses needed to deploy and
maintain dense heterogeneous networks. This critical advantage, along with
spectral efficiency, statistical multiplexing and load balancing gains, make
C-RAN well positioned to be one of the key technologies in the development of
5G systems. In this paper, a succinct overview is presented regarding the state
of the art on the research on C-RAN with emphasis on fronthaul compression,
baseband processing, medium access control, resource allocation, system-level
considerations and standardization efforts.
