Last year at Mobile World Congress in Barcelona, the first inklings of 5G were discussed. This year, 5G will probably be all over the place — and software-defined networking (SDN) and network functions virtualization (NFV) will play important roles, especially in terms of a new network topology.

The goals for 5G are 1,000-times higher system capacity; 100-times increase in data rates; connectivity enablement for 100-times more devices; latency reduced to 1 millisecond from 5 ms; and energy savings. So says Raj Singh, general manager of the wireless broadband group at Cavium.

There are several major pieces to the puzzle to achieve these goals, including spectrum coordination, creating multiple hierarchies, dark fiber, and cloud-based radio access networks (cloud RAN, or C-RAN). SDN and NFV will play in the multiple hierarchies and cloud RAN realms.

In terms of spectrum, those involved with 5G have their work cut out for them. Wireless spectrum comprises a hodge-podge of different bands, varying by geographic area and influenced by politics and competing claims. 5G may try to aggregate bands and also try to use bands that have previously been considered unsuitable.

But in terms of SDN and NFV, a big part of 5G technology will be the creation of multiple hierarchies, which will constitute the network topology. “Today, networks are flat, and everything goes back to the core,” says Singh. “5G creates hierarchical cores. Think of it as a multiple hierarchy of caches.”

Similar to content delivery networks, which cache popular content at the edge, 5G will cache content locally. But it will require an SDN controller to manage the traffic and orchestrate how the devices communicate. Hundreds of nodes may send data to an SDN controller. The different hierarchies will contain RAN radios of different sizes. Also, depending on the geographic locale, the network will have different degrees of hierarchy.

“If we’re going to achieve 1 millisecond [of latency], we can’t send all the way to the core,” says Singh.

The multiple hierarchies and SDN controller will allow traffic to be shifted dynamically based on need. “Today you have a base station in a location with a fixed capacity and bandwidth,” says Cam Cullen, VP of marketing with Procera. “In a virtual environment, you can dynamically shift the network for changing circumstances.”

Within the multiple hierarchy topology of the 5G network, there likely will be cloud RAN. “But you can’t have cloud RAN without having virtualized networks,” says Singh.

Already, Japan’s NTT Docomo and S. Korea's SK Telecom have fully centralized cloud RANs with dark fiber that goes to each radio head. “Today you need dark fiber for the fronthaul of cloud RAN,” says Singh. “Seoul and Tokyo have dark fiber all over the city, so it’s easy to do.” Dark fiber is necessary between the cloud RAN servers and the remote radio heads (RRHs) in order to meet latency requirements. But fiber is super expensive. Either cheaper fronthaul technologies will have to be developed, or cloud RAN won’t be feasible in all areas of the 5G network.

The 3G Partnership Project (3GPP) is the group that is grappling with 5G standards. In October 2015 it released a study looking at mobile core networks based on the architectural framework defined by the ETSI NFV Industry Specification Group.

There’s also a 5G-Infrastructure Public Partnership Project looking at new wireless technology standards in Europe.

NFV comes into play by helping to virtualize all the various appliances in the network.

“Mobile networks are migrating from physical to virtual,” says Procera's Cullen. “NFV is what controls the instances of the virtual base stations and virtual EPCs.”

In December 2015 Alcatel-Lucent (now Nokia) said it was working with some partners to commercialize virtual radio access network (vRAN) products, paving the way to cloud RAN.