L4S adoption sees T-Mobile writing ‘next chapter of 5G’

Low-latency, low-loss, scalable throughput (L4S) technology has been a standard part of wired broadband communications for some time, but not in scaled up wireless deployments. Now, however, T-Mobile US has stated that it has made this leap as part of a nationwide roll-out of a 5G Advanced network.

It was in April 2025 when T-Mobile announced that it was the first wireless network in the US to reach a critical milestone, with the country’s first nationwide 5G Advanced network designed to offer clear performance upgrades and support new use cases. It is also the first mobile network type specifically built to take advantage of artificial intelligence (AI), machine learning (ML) and network energy savings.

AI and ML are certain to become essential for future networks, given the predicted rapid growth in network usage and use case complexities that can’t be managed by legacy optimisation approaches with presumed models. System-level network energy saving is also a critical aspect, with operators needing to reduce the deployment cost but ensure network performance for various use cases.

5G-Advanced is engineered to bring more capabilities to enable wider use cases and enhance performance to a new level, promising to offer improved support for applications such as extended reality (XR) and promise monetary opportunities to consumer markets, with applications in gaming, video streaming, remote working and virtual training.

With L4S, T-Mobile said that it is deploying one of 5G Advanced’s most important capabilities and making a key step toward a smarter, programmable 5G. L4S is designed to deliver consistently low latency, minimal packet loss and real-time responsiveness even under heavy traffic.

“T-Mobile is the first to unlock L4S across a wireless environment at scale, and we’re already seeing the difference it can make…the next chapter of 5G is unfolding and T-Mobile is writing the opening lines,” said executive vice-president and chief technology officer John Saw in a blog post.

“Because everything flows through a single, optimised 5G core, we can deploy programmable features like L4S at scale while laying the groundwork for advanced network slicing and differentiated service tiers. As part of our broader push toward a programmable 5G network, we’ve also been testing L4S to explore how exposing real-time network data can help our partners and other innovators fine-tune their app experiences. That’s where the full value of this work starts to show up.”

The operator also announced trials and partnerships based on L4S. Looking at remote driving, T-Mobile said that it was partnering with Vay, a Berlin-based company developing automotive-grade remote driving technology, to show what L4S could do in “high-stakes, low-latency” scenarios.

Using the T-Mobile 5G Advanced network with L4S, Vay is said to have allowed remote drivers to experience predictable, consistent latency even in high-traffic, congested scenarios. The operator said that ultra-low lag and high responsiveness are a game-changer for mobility, logistics and time-critical safety applications.

In addition, it observed that tests in March 2025 with Qualcomm and Ericsson which looked to offer “immersion, without the nausea”, resolving latency and jitter issues that have held back the roll-out of XR.

The trials saw the use of a slim smart glasses form factor to put L4S to work on the 5G SA network and is said to have resulted in “crystal-clear visuals, ultra-smooth frame delivery”, significantly reducing motion sickness and dizziness.

Moreover, the operator said the trials underscored how L4S can pave the way for mainstream XR from niche to mainstream, especially in scenarios where comfort and continuity are essential.