C-RAN (Cloud-RAN), sometimes referred to as Centralized-RAN, is a proposed architecture for future cellular networks mainly driven by the following main operators requirements –
The traffic of each Base Station (BTS) fluctuates (called ‘tide effect‘); the average utilization rate of an individual BTS is pretty low and the processing resources cannot be shared with any other BTS. All BTS are designed to handle maximum traffic as opposed to average traffic, resulting in a waste of processing resources and power at idle times.
Moreover, traditional 1G and 2G cellular network consists of many stand-alone base stations (BTS) with its own cooling, back-haul transportation, backup battery, monitoring system, and so on that offer no cost savings.
For 3G, a distributed base station architecture was introduced with the radio function unit, also known as the remote radio head (RRH), installed on the top of tower close to the antenna and separated from the digital baseband unit (BBU) by fiber link. The digital baseband signals are carried over fiber, using the OBSAI or CPRI standard allowing more flexibility in network planning and deployment as they can be placed a few hundred meters or a few kilometers away.
C-RAN is an architectural evolution of the distributed base station system achieving large scale centralized base station deployment exploiting:
Real-time virtualization capability based on open platform: this is different from the traditional base station built on proprietary hardware, where the software and hardware are closed-sources and provided by one single vendor. C-RAN BBU pool is built on open hardware, like x86/ARM CPU based servers, plus interface cards to handle fiber link to RRH and inter-connection in the pool. Real-time virtualization insures that the resources in the pool can be allocated dynamically to different base station software stacks according to network load.
Cloud RAN is based on two tenets: centralization and virtualization of base station baseband processing.
While centralization is a means to improve performance with features like Coordinated Multi-Point (CoMP), the major driver for its introduction is operational cost reduction. About two thirds of a network’s cost of ownership is in operational costs including site rental, energy, and support and maintenance expenses.
On the other hand, the second tenet of Cloud RAN, virtualization, aims at reducing capital expenditure by applying network function virtualization (NFV) to the radio access network. Using commercial servers for base station hardware allows operators to leverage the economies of scale of the IT industry, additionally reducing by as much as 75% pooling and virtualizing baseband processing based on real-time needs and not on per site peak capacity.
Virtualization has another extremely attractive feature: switch between base station vendors can be done just downloading alternative vendor software
Azcom Technology is strongly supporting the C-RAN evolutionary path with its HW and SW solutions. The latest Azcom C-BBU product (AZB-NC0M-4304) and RRH CPRI based represent the basis for initial headway in BBU centralization and virtualization. The front haul and virtualization challenges are coupled in a manner such that a solution to both can be arrived at by judiciously choosing the functional split between centralized and distributed functions. Azcom Technology is actively building proof of concept solutions in this area that will eventually be the network architecture for 4.5G and 5G networks.