Rakuten Mobile has done some good work in building its open vRAN network. After some initial struggles and heroic engineering efforts, it’s on the air and it works. Hats off to CTO Tareq Amin and his team for proving that vRAN works.
But the problem addressed by Rakuten was one-dimensional: achieving coverage for a greenfield network. At least at first, high capacity is not necessary, as it has some time to build up the capacity of the network. As Rakuten plans for its future success, it clearly recognizes that further improvement is needed. Amin recently commented, "The part that I think the industry needs desperately to address and fix is the DU for radio access… I think the DU of the current open RAN platform is absolutely un-optimal. And it’s missing a lot of things to make it competitive.”
What he’s trying to say is that the virtual distributed unit (vDU) that’s available on the market, in most cases, can’t handle some of the high-capacity features of 4G/5G, such as Carrier Aggregation, CoMP and interference coordination. These features are instrumental in LTE networks deployed in single-vendor networks, where proprietary interfaces allow for coordination between radios and multiple DUs.
The industry will add those features. We can expect the O-RAN Alliance and other organizations to standardize interfaces that enable more advanced features in an open environment, and companies like Intel are doing great work to implement advanced vDU features in standard server hardware. Rakuten should be able to upgrade software for more capacity as it adds customers in the next few years…. like a Tesla customer boosting the performance of their car with a software upgrade.
The discussion doesn’t stop there. The greenfield networks (Rakuten and DISH) are a small part of the overall market. The real challenge is to virtualize a 5G network that coordinates new spectrum and existing radios in old spectrum. The old radios may be running LTE today, or they may have already been software-upgraded to 5G NR. They use dynamic spectrum sharing (DSS) in many cases to run both formats. They use Carrier Aggregation (CA), CoMP, eICIC and other features to squeeze capacity out of these crowded legacy networks.
The challenge is to virtualize without sacrificing the already-optimized legacy performance. Operators can’t give up CA and DSS to get the flexibility and scalability benefits of virtualization. That’s why we’ve seen some operators use a vCU only in their 5G deployment, not a full vRAN with both vCU and vDU.
As with the O-RAN networks, I believe that proprietary legacy networks will be able to implement a vDU and achieve high capacity performance at the same time. We see Verizon deploying the vCU with Samsung now, and Ericsson has launched its vDU with an ability to coordinate between new spectrum and 7 million existing radios in the field.
In fact, Ericsson coined the term "bluefield," instead of using the terms "brownfield" or "greenfield." The distinction is that a "brownfield" network is an anchor that the operator needs to drag around, like an old 3G network that is taking a long time to shut down. On the other hand, a "bluefield" network has the ability to use features like DSS and Carrier Aggregation to coordinate traffic across multiple bands and achieve high capacity. The legacy network turns into an asset, not a liability.
At a business level, the big question now is whether it’s too late for the vDU to get traction in the 5G cycle. We’ve already seen the huge 5G deployment in China without a vDU. We see some vCU deployment without the vDU in other advanced networks. Even the aggressive Korean and Japanese operators have held back on using a vDU. So a large fraction of the market has already moved forward without true vRAN. After installing dedicated DU hardware, nobody will rip it out to replace with COTS servers.
The time is now. The American C-band deployment is the last big opportunity to launch this technology at scale…or vRAN will need to wait a few years. Samsung has already deployed its vDU for Verizon in the low bands commercially, and is deploying the Verizon C-band vDU for its commercial service starting in a few months. We expect Ericsson to also deploy its vDU for Verizon’s C-band network this year. Both of these vendors are supporting advanced high-capacity features that maximize the combination of low-band and C-band radios.
In my forecasts, I recently predicted that we will see the American operators step forward and make the vDU work…driving a market for more than $4B of vDU software in the next few years. It’s starting to happen, and we have proof with success at Rakuten, followed by success in a coordinated "bluefield" network at Verizon.
Joe Madden is principal analyst at Mobile Experts, a network of market and technology experts that analyze wireless markets.
"Industry Voices" are opinion columns written by outside contributors—often industry experts or analysts—who are invited to the conversation by FierceWireless staff. They do not represent the opinions of FierceWireless.