Mobile network operators are under intense pressure to keep network operating costs in check as consumers demand more and more data while price wars keep a cap on the amounts carriers can charge for that data. Centralized radio access networks, or C-RAN, are an important tool for those carriers who have access to fiber, which is used to connect a centralized baseband processing unit to remote radios and antennas in the field.
Carriers can often leverage dark fiber for C-RAN, which can be less expensive than lit fiber. Dark fiber refers to strands in the ground that have not yet been activated by attaching optical connectors. When service providers lay down fiber, they often activate only the circuits they need. Since activating the fiber is referred to as “lighting up” the fiber, the activated circuits are called lit fiber. Sometimes carriers will light up their own fiber for a C-RAN deployment, and if that is not an option they may lease fiber.
Operators that are investing in C-RAN are often able to use this network architecture to control costs. There are at least three ways that centralized baseband units can help operators save money.
1. The baseband units are a shared resource for multiple radios. Network operators are in the process of deploying thousands of small cells in major U.S. cities. Antennas and radios are often attached to poles, but they cannot connect to baseband units at the bottom of the pole they way tower top equipment connects to BBUs at the base of the tower. There is no room on city streets for large BBU shelters, and even if there were, building one of these for each small cell would be cost prohibitive.
2. C-RAN offers flexible capacity. By centralizing the “brains” of the network, operators can allocate capacity as needed, in order to use spectrum and power more efficiently. Some analysts see C-RAN as an important step on the road to network function virtualization, which means the use of software to replace dedicated network hardware.
3. Real estate costs can be optimized. A shelter for a baseband unit does not need a fancy address of a conference room with a view. If fiber connections are available, these shelters can be located in places where real estate costs are lower than they are at the radio site.
C-RAN deployments can help operators control costs if the fiber is in place and affordable, but if fiber is unavailable or unaffordable, carriers may choose a different route. Sprint, for example, is eschewing C-RAN in favor of wireless backhaul for small cell deployments because it wants to move quickly instead of negotiating fiber leases in every market.
