Not all wireless operators are moving aggressively to software-defined networking (SDN), according to a top Nokia Networks executive. Instead, many operators are opting to start small and only test certain applications before committing to a widespread deployment.

“It’s really a process. Operators agree they have to do this, but the migration speeds are quite different,” says Volker Held, head of 5G marketing at Nokia. “Some are starting quite small by putting some dedicated NFV [network functions virtualization] in the core area or tackling the cloud and then seeing how that develops.”

But Held notes that having SDN and NFV functionality is key for wireless operators as they prepare to migrate from 4G to 5G. Even though the 5G standard has not yet been defined by standards bodies, Held says it’s clear that operators will need to be able to scale their networks quickly and carve virtual "sub-networks" or slices that can be then used for bigger bandwidth applications. That includes video, which might need throughput speeds of 10 Gb/s as well as lower bandwidth applications to connect devices that are less demanding on the network, such as smartwatches.

Held feels that, despite the varying speeds at which mobile operators are moving to SDN, most believe that 5G will incorporate a new network architecture, a new radio access network, and new business models.

AT&T has been fairly outspoken about its SDN deployments. At Mobile World Congress in February, AT&T executives touted the company’s Domain 2.0 strategy, which involves moving to a software-centric network architecture — making it easier for the company to test and eventually deploy 5G because it will give customers more control over the network.

In 2014, AT&T announced its SDN strategy and its goal of virtualizing 75 percent of its network by 2020. Last year, AT&T announced it had virtualized 5.7 percent of its network, and in 2016 it plans to expand SDN to 30 percent of its network. The company’s first big use case for SDN is Ethernet on Demand, which allows customers to increase or decrease their Ethernet services as needed.

AT&T says it has 14 million wireless customers on its virtualized network and will migrate millions more this year.