Software is eating the mobile network, but it's starting its meal in a very specific place. As wireless carriers embrace SDN and NFV, they're looking first to their mobile cores and moving outwards to their radio access networks.
The mobile core is a logical place to start given it's already largely centralized in metro networks. LTE evolved packet core gateways and policy management functions are among the first elements to make the transition -- as that core becomes virtualized, carriers will start looking to the edges of their networks where their workhorse base stations lie.
A new concept called the cloud-radio access network, or cloud-RAN, is starting to gain momentum in the mobile industry. The idea is that the highly distributed and specialized baseband processing functions of the network can be virtualized and centralized -- essentially moving the base station out of the cloud and into a local data center.
China Mobile Communications Corp. has long been a proponent of Cloud-RAN and it's currently trialing it using Alcatel-Lucent (NYSE: ALU) software and Intel Corp. (Nasdaq: INTC) Xeon processors. But other carriers from Telefónica to Orange (NYSE: FTE) have started pursuing the technology.
Here in the US, AT&T Inc. (NYSE: T) has an aggressive path to implement software defined networking (SDN) and network functions virtualization (NFV) throughout its wireline and wireless networks, and according to AT&T Senior Vice President of Architecture and Design Andre Fuetsch, cloud-RAN is definitely on the menu.
"We're very bullish on the cloud-RAN," Fuetsch said. "I don't have an exact date or timeline, but it's part of our plans." Radio access infrastructure is a huge part of AT&T's annual capital expenditure, Fuetsch said, so it makes perfect sense for the carrier to apply the cost savings and operational efficiencies of NFV to that critical component of its network.
And what are those efficiencies exactly? Cloud-RAN would create a common pool of shared baseband resources they could fluidly move between cell sites as demand in different network zones peaked and waned. For instance, during the workday, a carrier could concentrate processing capacity in the downtown business district of a city. As the workday ends, that capacity could flow out to the suburbs following commuters home.
Cloud-RAN is still a ways from commercial viability, but AT&T has plenty to keep it busy before it starts virtualizing base stations. AT&T has identified 200 individual functions across its wireline, wireless and transport networks, and Fuetsch said he's targeting them one by one. By the end of the year, AT&T plans to move 5% of its network off of dedicated hardware and onto NFV-based platforms. By 2020, AT&T hopes to have that transformation 75% complete. (See AT&T Details Software Shift and On the Cusp of Change.)
In wireless, AT&T is starting with LTE core, turning its packet data node gateways, serving gateways and mobility management entities into software functions. AT&T is also bringing IP multimedia subsystem framework into the cloud, allowing it to deliver applications and services across all of its networks and customer segments. For instance, it is starting to deliver VoIP across its consumer, enterprise and voice-over-LTE networks using a virtualized session border controller, Fuetsch said.
How far AT&T's virtualization trend extends to the RAN remains to be seen, Fuetsch said. The base station is a highly specialized piece of gear that won't necessarily slide easily into the data center. While carriers can move baseband processing into the cloud, the actual radios and antennas still need to remain on their towers and mounts, and their raw radio frequency data would need to be transported to the data center. That would require tremendous backhaul capacity, and because the mobile network is so limited by latency, those data centers would have to be relatively close.
"The network latency requirements are so high, and the digital signal processing needs are so great, that it's still too early to say what a definitive cloud-RAN architecture will look like," Fuetsch said. "The reality is the answer is going to be somewhere in the middle."
What Fuetsch means is that RAN likely will never be entirely virtualized and entirely centralized. Some baseband capacity will reside at the cell site, while some will be shared across cell sites in the cloud.
In fact, the virtualized mobile network may wind up looking a lot different than other types of NFV deployments in many ways. Instead of coagulating into a few data centers, the mobile network will retain its distributed nature, said Kevin Shatzkamer, CTO for mobile networking at Brocade Communications Systems Inc. (Nasdaq: BRCD)
Cloud-RAN processing will stick close to the towers it supports, residing in carrier central offices or neighborhood hosting facilities. Virtualized core elements will go into regional centers supporting multiple Cloud-RAN locations. Meanwhile, applications and services functions will be the most centralized, sitting in data centers serving vast swathes of the country, Shatzkamer said.
But the move to virtualization likely will go in the opposite direction, Shatzkamer said, starting with applications and moving outwards to the core and finally the radio network. And it's not going to be a quick process, he said.
"There is this belief in the industry that we're going to undergo this immediate transformation," Shatzkamer said. "That's not realistic."
— Kevin Fitchard, Freelance Technology Writer, special to The New IP