Yes, Rakuten will converge its 4G and 5G cores

All that work to virtualise the core, gone within 14-16 months of cloud core launch. CTO also eyes an IMS-less future.

Rakuten will have a single converged core network within 14-16 months of launching its 5G cloud core, its CTO Tareq Amin told a Light Reading online event today.

Rakuten announced yesterday that it would be working with NEC to co-develop a containerised, cloud-native 5GCore to enable Stand Alone (SA) mode. It is this version of 5G, along with the deicated 5GCore, that some think brings the true advantage of 5G into the market. That’s because it enables an operator to be more flexible in its service offering, and ability to innovate. Amin himself said, “ I don’t think NSA is exciting whatsoever. It just gets us out there with higher bandwidth for the user.”

To this point, Rakuten has been working on a virtual EPC (vEPC) with virtual core network functions from different providers, including Cisco. It has been innovative, but also hard work, and still hasn’t got Amin to where he wants to be.

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, w e are not completely satisfied with where we want to be. 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. In the VM 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.”

The solution, then, is to move to the cloud native world, with containerised, stateless functions deployed as microservices in a service-based architecture.

“In probably 14-16 months we are anticipating to have one single converged core”

Amin: “In the 5G Core era everything must be cloud-native, with the architecture of microservices built around stateless. Our objective is to deploy on our own cloud platform, and we have pushed NEC to think differently, to push hard to the open core,  with source code sharing and joint innovation, not to be another vendor bringing proprietary innovation.”

Amin said that would mean Rakuten will have both its virtual 4G core (vEPC and NSA 5G core), and its cloud 5G Core. But then it will converge all the 4G elements into the cloud platform, “to start the migration of everything in VM into the RCP (Rakuten’s cloud platform) containers platform. That’s really important to achieve.”

Event moderator Gabriel Brown kindly put a question submitted by TMN to Amin, asking him if he would run the 4G/NSA and 5G cores concurrently. Answering, Amin said that it would take a while to get the 5G core up and running, but he envisaged “collapsing” the 4G core into the new cloud platform within 14-16 months.

“The most challenging thing to achieve in the 5G core is the completion of a highly scaleable, high throughput User Plane (UPF).  The Control Plane functions are relatively straightforward. But we want to achieve a very good throughput on our UPF containerised architecture, so we are spending considerable time with NEC on the feature.

“So to finish that development, the timeline is as follows. The 4G vEPC that we have today will run with NSA to get us through our launch for 5G. When we launch our 5G Core, for a period of time they will run in parallel – however the strategy is that the 5G core, once built, with all containerised functions and components, will collapse all of the 4G functions and in probably 14-16 months we are anticipating to have one single converged core  -100% pure cloud native functions on the RCP.”


Amin added within the session that the operator is seeing more voice on RCS than VoLTE, driven by usage of its communications app Link, which it built as an alternative to the native “dialler”. That may soon move into UCC, he said, delivering an IMS-less future.

Amin: “We are carrying more voice calls on RCS than VoLTE, allowing us to move away from a 30 year old implementation of a native dialler into competing with OTT apps. Voice in Rakuten is an app – Link – based on RCS moving quickly into UCC (Unified Communications and Collaboration), and maybe we will get into an IMS-less architecture with UCC.”