T-Mobile is rolling out a new network feature called L4S – short for Low Latency, Low Loss, Scalable Throughput – as part of its 5G Advanced upgrade. It’s already live in several cities in the US, and more are on the way.
The company says its L4S feature helps keep latency low, cuts down on data loss, and improves responsiveness, even when networks are busy. That makes it useful for things like cloud gaming, XR headsets, video calls, and remote driving. Wired networks have used L4S for a while, but this is the first time it’s being scaled in a wireless network in the US.
T-Mobile CTO John Saw told The Verge users don’t need a new phone or a special plan to get the benefit – the changes happen on the network side.
The company says its 5G Advanced network is built differently from older systems still running on 4G cores. Because T-Mobile uses a standalone 5G core, it can roll out features like L4S more easily and continue to add more advanced tools, like network slicing. The idea is to offer more flexible network performance depending on what an app or device needs.
According to T-Mobile, the approach also makes it possible to share real-time network data with developers, letting them tune how their apps respond to changing conditions.
Remote driving gets a boost
One test case is remote driving. T-Mobile worked with Berlin-based company Vay to show how low-latency wireless connections could help drivers operate vehicles from a distance. With L4S running on the 5G Advanced network, Vay’s remote drivers reported a steady connection that didn’t feel delayed, even in areas with heavy traffic.
T-Mobile also ran XR trials with Qualcomm and Ericsson. In the tests, a slim pair of smart glasses was used to stream immersive content over the L4S-enabled network. The company said users saw clearer visuals, smoother motion, and didn’t suffer with as much motion sickness – all of which are common complaints with XR. The tests suggest L4S could help bring XR closer to mainstream use.
Smoother cloud gaming
Cloud gaming is another area where L4S is already in use. NVIDIA has added L4S support to its GeForce NOW service. On T-Mobile’s network, players report seeing less lag and fewer dropped frames, and the experience felt closer to playing on a console, according to the company.
L4S may also help with video calling, especially in crowded places like airports or stadiums. The network can adjust in real time to avoid frozen video or broken audio. T-Mobile says it’s been testing this feature with common apps like FaceTime.
A step toward programmable networks
T-Mobile sees L4S as a building block for more customisable network features. In the future, the company plans to use L4S to offer different performance levels for apps like gaming, XR, or live video – depending on what’s needed.
There’s also interest from partners. By sharing live network data, like how busy a radio tower is, T-Mobile says developers can better tune their apps to work with network changes in real time.
L4S is part of the broader 3GPP Release 18 spec, and T-Mobile says it will be built into its future enterprise offerings. While the feature is still being rolled out, the company says it’s close to launching more commercial uses.
(Photo by Mika Baumeister)
See also: T-Mobile expands Starlink beta to AT&T and Verizon
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