How are operators approaching standalone 5G?


T-Mobile’s 600 MHz standalone 5G network

In Early August, T-Mobile claimed a world’s first with the launch of a nationwide standalone 5G network that uses its 600 MHz spectrum. T-Mo initially launched its 600 MHz 5G network last year and reached nationwide coverage–200 million people covered–using the non-standalone architecture. With the shift to standalone, the operator saw a coverage expansion of 30% to 1.3 million square miles, upping population coverage to 250 million, and a 40% reduction in latency. 

Before we look ahead, let’s look back at some milestones in T-Mobile’s journey to standalone. In August 2019, T-Mobile completed a standalone 5G over the air data session using multi-vendor kit in a Bellevue, Washington lab. Vendor support came from Ericsosn, Nokia, Cisco and MediaTek. 

T-Mo announced another round of standalone activities in May of this year. Working with Ericsson, the companies completed a standalone 5G data session between commercial modems on a production network. They also completed a low-band standalone 5G voice call with a mechanism to fallback to Voice over LTE (VoLTE), along with low-band Voice over New Radio (VoNR) and Video over New Radio (ViNR) calls.

With the standalone 5G network up and running, T-Mobile Vice President of Radio Network Technology and Strategy Karri Kuoppamaki told RCR Wireless News,  “It’s a huge step forward in our evolution and our plan to bring 5G for all–to everyone everywhere.”

T-Mobile is following a 5G spectral strategy it often compares to a layer cake. The low-band 600 MHz network provides wide area coverage, 2.5 GHz spectrum acquired from Sprint brings a balance of coverage and capacity, and millimeter wave deployment is reserved for urban cores and other dense user environments. 

“The benefit of SA is that it sort of breaks the dependency on mid-band spectrum which is sort of the anchor for 5G in non-standalone mode,” Kuoppamaki said. “This then allows us to bring 5G on low-band to areas that didn’t have 5G.” But the transition is about more than just coverage expansion, he said. “The last [benefit], which I think is probably one of the most important benefits of this as well, is that it’s really sort of a key to our 5G future and many of these advanced features that talked about in 5G.” 

Asked about VoNR, Kuoppamaki said it’s not supported today but, “We’re working very hard to introduce Voice over NR.” Discussing how traffic is managed in areas where standalone 600 MHz 5G and non-standalone 2.5 GHz 5G are both available, he said, “Non-standalone and standalone are not mutually exclusive,” noting the ability to transition between the networks based on application demand from the UE. “This is an ever-changing scenario,” he said. 

“What drives us is obviously the best customer experience and best speed experience. I’d say that there are a couple of different cornerstones to our strategy. One is to push 5G evolution forward very, very aggressively. We’re never going to be happy with where it’s at at any point in time. The second piece is to deploy the spectrum assets we have more broadly. The third one is just in general to improve the network and its coverage across the board. I think those are the types of things that are pushing us over time.”

Rakuten Mobile’s move from vEPC to cloud-native 5G core

Rakuten Mobile, the mobile operator subsidiary of Japanese e-commerce giant Rakuten, launched LTE services this year on top of a fully-virtualized, greenfield network composed of 330 “far edge” sites connected to 58 regional data centers hosting vRAN workloads, and three central data centers that primarily host control plane workloads. The operator currently uses a virtualized evolved packet core built following a Control and User Plane Separation (CUPS) architecture for LTE services. 

Speaking during Light Reading’s 5G Networking Digital Symposium in June, Rakuten Mobile EVP and CTO Tareq Amin discussed the company’s roadmap for evolving its core network to non-standalone and standalone architecture. On CUPs, “We felt this was mandatory and necessary if you wanted to offer local breakout and true edge applications. We really pushed very hard to enable this and enable it at scale.” 

With its vEPC, Rakuten Mobile has used a microservices-based architecture wherein software is decomposed into loosely coupled bits that can be rapidly rearranged into various applications. “In our network,” Amin said, “because of the microservices architecture that we have implemented, we could really have [an]infinite number of UPF and control plane functions. Whatever happens at any instance of time in data center one, we could in real time be able to carry the session in data center two or three and be able to manage this traffic.” This ability to automatically move a workload “started to point to possibilities and ideas” about what a cloud-native architecture can enable. 

While Amin said the 198 unique virtual network functions Rakuten Mobile has deployed as virtual machines running on OpenStack is “amazing” compared to a proprietary implementation, “There is a lot of things that are missing–quite a bit actually. As elegant as this VM architecture that we have done is, we are not completely satisfied. We need to get to a state in which we are able to truly, truly have elasticity…You never worry about capacity anymore.” Which brings us to the coming transition of the core network to a cloud-native architecture. 

Looking ahead to the activation of non-standalone 5G and then the transition to standalone, as well as the future trajectory for the LTE network’s vEPC, Amin said the mission is to deploy all of it on the company’s own cloud platform. Rakuten Mobile is working with compatriot firm NEC on what Amin described as an “open core.” That collaboration considers joint development of a container-based standalone core using source code developed by NEC. The two firms are also collaborating on manufacture of 5G radio units. 

Amin laid out his thinking on using the LTE vEPC to support a non-standalone launch, then discussed the next step. “The most challenging thing in the cloud-native 5G core, in my opinion, is the completion of a highly-scalable, high-throughput UPF. I think the control plane functions are relatively straightforward. We want to achieve a very good throughput on our UPF containerized architecture. We’re spending considerable time with NEC on the development of that feature. I don’t think NSA is an exciting thing whatsoever. It just gets us out there with higher bandwidth and higher speed for the end user. This is now where we want to be. When we launch our 5G core, for a period of time we will run them in parallel. But 5G core, once built with all containerized functions and components, will collapse all the 5G functions” into a single, converged cloud-native core.

Vodafone U.K.’s standalone network at Coventry University

Vodafone U.K. sees standalone 5G as a key enabler of advanced use cases like autonomous vehicles, smart manufacturing, remote surgery and the “internet of senses,” according to materials published by the operator. In pursuit of that future, the operator in July deployed a standalone 5G network at Coventry University that will be initially used to enable virtual reality-based training for “student nurses and allied health professionals,” the company said. The network uses equipment from Ericsson, MediaTek, OPPO and Qualcomm. 

Coventry University’s Vice Chancellor John Latham said the standalone 5G network “will help us continue to change and enhance the way students learn” and added that the institution’s goal is “creating a 5G campus…We will soon be able to reveal how we will use this technology to maximize the potential of virtual reality teaching for our Health and Life Sciences students.” 

Vodafone U.K.’s Chief Technology Officer Scott Petty said the current focus of 5G is “increased speeds…but it’s only the tip of the iceberg of what 5G can do. With this new live network we’re demonstrating the future potential of 5G and how it will be so valuable to the U.K. economy…From here, we will really start to see 5G make a difference to the way organizations think about being connected, and what’s possible with connectivity in the future.” 

Among the chief benefits standalone 5G enables, Vodafone U.K. calls out network slicing (more on this later). The operator also notes that the distribution of computing power closer to where data is generated is key to fully realizing the latency reductions made possible by standalone. 

Vodafone U.K. has offered commercial 5G service since July 2019 and has availability in dozens of cities as well as elsewhere in its multi-national footprint, including Ireland, Italy, Germany and Spain. 

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