Open RAN

Open RAN is a way of building a mobile network in which the tower's radio hardware comes from one company and the software that runs it comes from another, joined by a common, published standard. RAN stands for radio access network: the radios and antennas on towers, and the computers that process the signals between your phone and the network. Traditionally, an operator bought the whole RAN from one equipment maker, as one locked package.

Here is how it works in general. The RAN is split into parts. The radio unit sits on the tower and sends and receives the wireless signal. The work of processing that signal, called the baseband, is split into a distributed unit near the tower and a centralised unit further back in the network. Open RAN publishes the rules for how these parts connect. The split between the distributed unit and the centralised unit comes from 3GPP, the body that writes the mobile network standards. Most of the other open rules, including how the radio unit connects to the distributed unit, are written by an industry group called the O-RAN Alliance. Because the rules are open, the radio unit can come from one maker, and the baseband software can run on an ordinary server bought from another. A further part, the RAN intelligent controller, lets apps from other companies tune the network, for example to switch off some radios at night to save power.

Why would an operator want this? With more makers able to compete, prices may fall, and the operator is not tied to one supplier for decades. Some governments also want to depend less on a few equipment makers. The difficulty is that parts from different makers must work together perfectly. Towers must stay in step with each other to within about a millionth of a second, so testing and joining the parts takes a lot of work.

Take, for example, Rakuten Mobile in Japan, which built a new national mobile network on this approach.

Consider a port that wants its own private 5G network for its cranes and vehicles. It can buy small cells and software from smaller companies, and run the network software on its own servers.

For instance, a chip start-up can sell a 5G baseband chip that puts a base station's processing on one programmable chip. That business depends on how far open towers spread.

The products involved are radio units and antennas and RAN software, and the network they build is usually 5G.

How is Open RAN different from hardware-software disaggregation? Disaggregation is the general idea of pulling software off sealed boxes, in switches, phone systems and storage. Open RAN is that idea applied to the mobile tower. It is also different from virtualised RAN, in which the tower software runs on ordinary servers but may still come from the same maker as the radio.