Virtualization is a technique for wireless operators seeking to reduce capital costs and increase flexibility in their networks. To date, virtualization has focused on NFV for hardware-based functions, and cloud-RAN (C-RAN) enables NFV for mobile base station hardware.
C-RAN is an acronym commonly heard in the wireless industry these days — the term does, in fact, have a couple of different meanings. The C in C-RAN stands for both “centralized” radio access network (RAN) and also “cloud-based” RAN. They are related concepts.
In a traditional distributed cellular network, the RAN is the part of the network that we think of as a cell site, with equipment at the top and bottom of a cell tower. Its primary component is the baseband unit (BBU), which is radio equipment that processes billions of bits of information an hour and links the end user to the core network.
Until recently, the BBU was almost always located on-site near the bottom of the tower in some type of shelter or enclosure. The network operators had to lease the space, run power to every BBU and cool the equipment inside. Add it up and about two-thirds of a wireless network’s total cost of ownership is in operational costs such as site power and cooling.
C-RAN provides a more elegant and efficient alternative. By leveraging fiber’s huge signal-carrying capacity for fronthaul, operators can centralize multiple BBUs in one location, either at a cell site or at a centralized BBU pool location. Centralizing multiple BBUs simplifies the amount of equipment needed at each individual cell site and presents a host of other key advantages, such as lower latency.
The ultimate end-game of C-RAN, though, is Cloud-based RAN, which is when some network functions start being virtualized in “the cloud.” Once the BBUs are centralized, commercial off-the-shelf servers can handle much of the routine processing. This means the BBUs can be redesigned and scaled back to focus on the complex or proprietary processing. Centralizing base station processing with Cloud-based RAN simplifies network management and enables resource pooling and coordination of radio resources.
Cell virtualization — an emerging capability enabled by C-RAN architectures — extends the concept of virtualization beyond hardware and into the airwaves. It provides a way for operators to deliver more capacity on a given amount of spectrum without introducing cell border interference. Like network functions virtualization (NFV), cell virtualization delivers capacity more dynamically, where and when it is needed.
Cell virtualization dynamically creates virtual non-interfering sectors on a per physical resource block (PRB) basis.
C-RAN-enabled cell virtualization lets wireless operators re-use spectrum many times over within the footprint of a single cell by dynamically defining virtual sectors. The result is multi- sector capacity without cell border interference, for a significant increase in user data rates, especially at the cell edge.
Device battery life improves because the user devices need only track a single cell and because they transmit at a lower power level. Deployment is faster and lower-cost because much of the tedious RF planning is eliminated.