T-Mobile is bringing low-latency tech to 5G for the first time

Over the next few weeks, T-Mobile is expanding support for the L4S standard, which stands for “Low Latency, Low Loss, Scalable Throughput.” The technology helps high-priority internet packets move along with fewer delays, to make video calls and cloud games feel smoother and reduce annoying hitches.

Users won’t need a special phone or plan to take advantage of the benefits from L4S. “This is network-driven,” T-Mobile CTO John Saw tells The Verge.

L4S is already deployed in “many cities” on T-Mobile’s 5G Advanced network, but the company is “actively expanding” the coverage, company spokesperson Anushka Bishen says. Saw says T-Mobile is the first wireless network in the US to implement L4S. 

The L4S standard helps devices manage congestion with internet packets so that you’re less likely to hit a pause if that congestion leads to buffering and latency, which can still become a problem even on higher bandwidth connections like upgraded 5G networks. With L4S, packets get an indicator that will get marked if they experience congestion, and devices can read those packets to make adjustments to hopefully reduce that congestion and maybe even eliminate it.

Saw used a car analogy to help explain it: “In the olden days, you used reactive braking when traffic slows down. L4S is more like dynamic cruise control, where the car actually automatically slows down and speeds up without you having to jump in.” If you want to read more, my former colleague Mitchell Clark has a detailed explainer of how it’s supposed to help.

For users, this means that applications that support L4S should experience less latency. In a blog post, Saw highlights how L4S can benefit things like Nvidia’s GeForce Now and Apple’s FaceTime calls. Both Nvidia and Apple also worked with Comcast during its trials of L4S, and Comcast started rolling out L4S to some cities earlier this year.