The success of open radio access networks (RAN) will ultimately be gauged by how much of the architecture is deployed in commercial networks, according to Sachin Katti, co-chair of the O-RAN Alliance’s technical steering committee. 

There are three aspects of open RAN involved in that endeavor, including disaggregation of the different elements of the RAN, the use of commoditized hardware, and network virtualization, he explained. 

“I see a lot of steam, a lot of progress on disaggregation already,” Katti told SDxCentral. “Every tier-one operator that I talk to around the world now has plans to deploy the radio hardware in a disaggregated manner from the baseband software, so the radios that go on top of cell towers, especially as 5G rollout happens.”

Virtualization and commoditized hardware have also experienced “significant progress” during the last 18 months, according to Katti, but a lot of work still needs to be done.

“We see for example that deployments are already beginning to do the disaggregation of the radios on the cell tower with the baseband software and they are already beginning to do some of the virtualization, but the decoupling of the control is still something that we do not see in deployment yet,” he said.

That decoupling is also important to edge computing for use cases that require low-latency. “A lot of those will depend on the applications that are running at the edge having visibility and control into the access network infrastructure,” explained Katti, who also co-founded Uhana, an artificial intelligence (AI) startup that was acquired by VMware to bolster its 5G efforts in July 2019. Katti now serves as VP of strategy, telco, and edge cloud at VMware.

“If they are just another application that is going to run on top of the network without any integration or visibility from the network, then the only thing you’ve really done is change the placement point of that application to the edge cloud,” he added. “To really kind of differentiate and deliver differentiated edge cloud or edge computing experiences, interfaces into the network are actually a critical component of it, so the network API. I think that control plane piece and decoupled control is not just for better network management, it’s actually for how do you deliver these differentiated edge applications on top.”

Startups like Altiostar, Mavenir, and others are trying to make their mark but there hasn’t been much success from smaller vendors in RAN to date and that “has really hurt the whole industry because there’s not been a lot of innovation in RAN. It’s not like there’s been a new baseband that has really come out,” Katti said. 

"Every incumbent vendor has its own opinion about open RAN. Huawei, for example, is not even part of [the O-RAN Alliance] and they think it’s a fool’s errand to try and run the RAN on commodity hardware. They’re doubling down on using proprietary hardware for the RAN. Similarly, Ericsson also I think is on the record saying that they don’t think it makes sense to use commodity hardware for running RAN workloads,” he said. “At the same time, I think Ericsson sees a lot of merit in opening up interfaces into the RAN infrastructure for automation, policy, slicing, these kinds of capabilities, so they have been sharing that part of the effort." 

There is also ongoing debate among the big RAN vendors around the use of commoditized hardware and interfaces to program the RAN. “A key component of the ORAN architecture is an SDN-style decoupling of control from the underlying data plane,” he said, adding that most implementations from the existing vendors tightly integrate the control plane inside the baseband software. 

During the next three years, Katti expects there will be an incremental hardening of the open RAN ecosystem paired with architecture frameworks that can be deployed at scale. And during the next five years, the industry will start to see a critical mass happen as more operators upgrade network infrastructure.

“No one is going to rip out and replace their existing LTE network to do this. They’re going to take the opportunity when the 5G rollout happens,” he said. “Even if it technically succeeds right now it will still be tied to kind of when rollout decisions happen around 5G.”

Among operators that are already in the midst of 5G operators, open RAN will be deployed as an overlay on top of the existing infrastructure rather than a replacement, he added. 

Greenfield networks like Rakuten Mobile, which recently launched a virtualized, cloud native, and open RAN network in Japan, provide a positive example of virtualized RAN running on multi-vendor and commoditized hardware. But it has a ways to go before it reaches the full vision outlined by the O-RAN Alliance and others, according to Katti. 

Rakuten Mobile’s radios for its 4G LTE network are not disaggregated or using open interoperable interfaces, but the operator is expected to achieve that in its evolution to 5G later this year, he explained. 

“The next step of this will be: Can an operator deployment succeed without having the kind of integration exercise that Rakuten did for both [virtualized] RAN as well as this disaggregated radio? I think that will be the next test, and the last phase will be around these interfaces which decouple the control,” Katti said.