Rakuten Mobile’s network deployment has been atypical in so many ways, including the fact that so many elements will have a very short life.
Most operators aim to prolong the life of their network assets for as long as possible, even though that sometimes leads them to prioritize backwards compatibility over performance when choosing a next-generation equipment vendor. But Rakuten, having only recently switched on a 4G network with macrocell radios from Nokia and a core from Cisco and others, will turn to NEC for its 5G radios and core.
While the Nokia radios will be in action for as long as 4G is run alongside 5G (several years at least), the 4G core could be phased out in just 14-16 months, according to Rakuten’s CTO Tareq Amin, as he aims to have a single converged, cloud-native core in that timeframe.
The strategy highlights some of the challenges of the Rakuten approach. It was working under tight regulatory deadlines to launch 4G services, which forced it to deploy the 4G network first, even though 5G was to follow later the same year. In an ideal world, it might have had spectrum ready so it could go 5G-only, or at least with a 4G/5G SingleRAN platform, from day one, rather than building what is looking like, in effect, a stopgap network on the way to 5G.
And while the network has been widely touted as the first end-to-end cloud-native mobile platform, in fact the first, 4G phase is not entirely cloud-native. The evolved packet core, developed with Cisco and other partners, is based on virtual network functions (VNFs) rather than cloud-native functions (CNFs) alone, for instance. This is not to denigrate the achievement of deploying a fully virtualized, end-to-end network in a comparatively short time. And in the case of the RAN, there is a smooth migration path from 4G to 5G, with Altiostar providing VNFs and CNFs that will run on the 4G and 5G radios from Nokia, NEC and Airspan.
But as the famous saying goes, ‘you wouldn’t start from here’, and the hefty inhouse engineering team that Amin had to assemble to integrate all the elements from his 20-plus suppliers are likely to have to stay in place to handle the migration, in a way that will not compromise the experience for the 4G users.
Speaking at an online LightReading event, Amin talked about the recently announced plan to co-develop a cloud-native 5G core with NEC (this will also be offered to other operators as part of Rakuten’s plan to package up and license its mobile platform and establish a global marketplace to expand it).
He said: “What we have learnt from our first phase in Rakuten is that going from proprietary to virtual was a maze. We have deployed 198 unique VNFs, but there are a lot of things that are missing. As elegant as this architecture that we have done is, we are not completely satisfied. We want to get to a state where we can truly have elasticity, let the containers manage themselves and scale in and out based on demand.”
He continued: “In the virtual machine world it’s not as easy, simple and orchestrated as you might want to believe. It has been a difficult, super difficult, journey because with these VNFs we have to spend significant energy to bring common orchestration, and we are still nowhere close to where we need it to be.”
He said the single converged core should be in place in “probably 14-16 months” and added: “Our objective is to deploy on our own cloud platform [RCP], and we have pushed NEC to think differently, to push hard to the open core, with sourcecode sharing and joint innovation, not to be another vendor bringing proprietary innovation.”
The 4G elements will be converged into the cloud platform “to start the migration of everything in VM into the RCP containers platform”. According to Amin, the current vEPC will support the initial 5G launch in Non-Standalone mode, and will then run in parallel with the 5G core for a period of time before collapsing the 4G functions into the new platform. The most challenging task will be to develop a very scalable User Plane architecture with very high throughput, he added.