Virtualized RAN has so far been a big disappointment to operators. The more bullish ones expected to start deploying it in the latter stages of 4G, improving the flexibility and cost of their networks even before 5G arrived. In reality, operators wanting to make an early start on 5G have faced a choice of adopting conventional architecture, since standardized, affordable vRANs are still not available; or investing in something hand-crafted and expensive (as SK Telecom has, for instance).
But vRAN still lies at the heart of the planned transformation of network economics, which will be essential to justify 5G deployment at scale. And Nokia believes the acceleration of 5G roll-out in some markets will have a knock-on effect on the availability of vRAN in the mainstream.
The company’s north America CTO, Mike Murphy, told FierceWirelessTech that there will be fully commercial products available in 2019, earlier than many had expected, with the focus mainly on 5G, or on flexibly integrated 4G/5G networks. He does not expect this to be a mass market for a couple more years, but at least advanced 5G operators will be able to start moving towards vRAN where this will make a significant difference to their service capabilities and ROI.
Nokia is working with Verizon and Intel on the US operator’s ‘vRAN 2.0’ platform, which – despite its name – will move “everything but the radio network” into the cloud. Both Verizon and AT&T have aggressive virtualization programs, but both have acknowledged that the RAN is the most difficult network element to implement in software, and the one with the most uncertain ROI, so it will come at the end of their multiyear roadmaps.
However, Verizon has started trials of vRAN, and some implementations, particularly in localized small cell networks and in pre-commercial 5G. It announced vRAN 2.0 in February, and first trials took place in Oklahoma City, with the virtualized baseband functions running on Nokia’s AirScale cloud base station server, based on Intel’s Xeon processors. Verizon has also run vRAN trials with Ericsson and Samsung as part of its broad Open RAN initiative in 4G and future 5G.
The new architecture builds on existing centralized, but non-virtualized, units which Verizon calls cRAN hubs. Nicola Palmer, the operator’s chief network engineer, said: “We have thousands of these cRAN hubs throughout the US. They’ve already been identified. They are built out and equipped. And we have been in the process of centralizing those baseband units.”
She explained that, as a result, 15 to 50 centrally managed cells could work together, using LTE-Advanced features like remote electrical tilt (RET), which can point an antenna array toward high traffic areas during the day and then tilt them up at night to improve coverage.
The next step is to “do a lot more … The cRAN hubs become vRAN hubs, and now you can communicate across cRAN hubs. … You can scale horizontally instead of vertically.”
Verizon has also started to virtualize some functions in the upper layer, or Layer 3, of the network, within its own cloud architecture. This is not all about 5G, though it will go hand-in-hand with New Radio roll-out as that progresses. Some of the benefits of vRAN come from having a common set of functions in the centralized, white box baseband unit (BBU), which can work with remote radio units (RRUs) supporting different standards, and potentially from different vendors. This gives the MNO flexibility to swap new radios in and out only as required, rather than engaging in a complete upgrade.
“We’re going to proceed down that path with 5G NR as we get in into the NR deployment phase now,” Stone said. “We’re also going to … virtualize the upper layers for LTE as well.”
Stone said Verizon is working with its vendors—Ericsson, Samsung and Nokia—to virtualize the lower layers of its network too.
Meanwhile, Telecom Italia is also taking steps towards a commercial vRAN. It has, in the past, run trials with Huawei and others, but is now working with Ericsson on a deployment in the city of Turin. It claims this will be the largest LTE vRAN in a major city.
The operator has deployed cloud-based NFV infrastructure and virtualized 40 network functions, for instance, those concerned with mobile traffic optimization and VoLTE management.
In February, TIM and Ericsson announced they would digitalize TIM’s nationwide RAN, starting in Turin, to improve cost efficiency and customer experience. In tandem with virtualizing RAN functions, they are working on automation, especially self-organizing network (SON) technology, to reduce TCO and, in the specific case of voice, reduce the number of servers to support VoLTE services.
The Turin deployment is part of TIM’s DigiTIM digital transformation project. It will form the basis of an eventual migration to 5G, which will be used, in particular, to extend the RAN’s services to machine-to-machine applications, from a unified network database.