For the cellular edge access, SoftRAN [3] and OpenRadio
[4] are the latest proposals aiming at bringing the power of
SDN to innovate the wireless access domain. SoftRAN focuses
on the control plane design by abstracting multiple
base stations into a virtual big base station. A 3D resource
grid is defined by SoftRAN to allow operators to manage
the radio resources within a geographical area through
three dimensions – time, frequency, and base station index.
The SoftRAN controller maintains a RAN information
base (RIB) which can be accessed by various control modules
for radio resource management. The RIB consists of
essential information to be updated by the controller, such
as the interference map, flow record, and network operator
preference. As the radio element has a more timely view of
the local state than the remote controller, SoftRAN further
optimizes the control decision by splitting the control
functionality between the central controller and the radio
elements.