T-Mobile rolls out a cloud-native, 4G/5G converged core gateway

**12/15/22 Update. After publication of this story, T-Mobile sent additional information found at the bottom of this story.

T-Mobile today said it worked with Cisco to launch a distributed, cloud-native, converged core gateway. And T-Mobile has now moved all of its 5G standalone (SA) and 4G traffic to the new cloud-native, converged core.

Previously, we haven’t heard operators talking about a “converged core.” They’ve talked about non-standalone where the 5G RAN still uses the 4G core. And they’ve talked about standalone (SA), which uses both 5G in the core and in the RAN.

In 2020 T-Mobile announced that it had a nationwide 5G SA network running on its 600 MHz spectrum. And it recently announced its was rolling out 5G SA on its 2.5 GHz spectrum.

So, T-Mobile's 5G SA network is now using 5G in its core and RAN.

Telecom industry consultant Chetan Sharma, said, “The idea is to serve everything from the same core. But 4G is not going away. It will stay for a long time for coverage. They are trying to converge the two networks as much as possible to decrease costs.”

Hence, T-Mobile’s use of the word “converged.”

A converged core gateway basically connects together a 4G LTE evolved packet core (EPC) to a 5G core network. Previously, two separate core networks operated independently. Now, they can “converge” their data into a single bucket that allows for faster data speeds.

And what about devices?

Many of T-Mobile’s customers can access its 5G New Radio (NR) network because they use 5G phones. However, some people have not upgraded their devices or they use their devices where 5G is not yet currently available. In those locations, they may be using 4G LTE. By bonding together the 4G LTE network with the 5G network with the converged core – T-Mobile is able to migrate all the data to the 5G network.


T-Mobile also said today that it worked with Cisco to make its converged core cloud-native.

The definition of “cloud-native” entails a complicated set of features. But one of the cornerstones of cloud-native is the use of containers.

T-Mobile’s converged core architecture is based on Cisco’s cloud-native control plane, optimized with Kubernetes-orchestrated containers on bare metal. The container-based technology frees up over 20% of the central processing unit cores. T-Mobile said the move to the cloud-native core has immediately boosted performance for customers with more than a 10% improvement in both speed and latency.

The converged core uses a broad mix of Cisco technology including the Cisco 8000 Series routers, 5G and 4G packet core gateways, Cisco Unified Computing System (UCS), and Cisco Nexus 9000 Series Switches with Cisco Network Services Orchestrator for full stack automation.

Distributed core

According to T-Mobile, its 5G SA core is distributed nationwide. AT&T has made similar statements about distributing its 5G SA core.

A nationwide distributed core network means that the core will be able to serve a very significant portion of the population in the U.S. Both T-Mobile’s 5G and 4G LTE networks are already nationwide, so the deployment of this converged gateway makes this functionality available across that very wide footprint.

T-Mobile also said the new converged core gateway allows it to shift resources with better agility to other services like 5G Home Internet. It also will expedite time to market for new 5G services like network slicing and Voice over New Radio (VoNR).

For VoNR, calls that originate or terminate on Voice over LTE (VoLTE) devices can more easily access the 5G network and interoperate with 5G NR devices.

**12/15/22 Update

After publication of this story T-Mobile sent the following information:

“Converged” means that the same platform is handling all SA 5G traffic, in addition to all LTE traffic and NSA 5G traffic. Previously we had a core for SA 5G traffic and a core for LTE and NSA 5G traffic. Now we no longer have two separate cores.

The core is distributed across T-Mobile facilities and on-premise private cloud, using Cisco infrastructure. We now have one core, so effectively the same distribution applies to both 5G and 4G traffic.

There is no change to the VoNR experience. This platform already carries VoNR traffic in markets where VoNR is launched, and it’s ready to support new VoNR markets as they launch in the future.