What is L4S?

This may sound technical, but basically, it is a technical function that ensures that data in the mobile network is transmitted faster, more stable and without interruptions.

Why is L4S so important?

In many modern applications such as online gaming, video conferencing or virtual reality (VR), every millisecond counts. When the network is congested, there will be delays, stuttering or the picture will freeze – this is also known as "lags". This is not only annoying when gaming but can also cause serious problems in professional use - for example, when remotely controlling machines or vehicles.

This is exactly where L4S comes in: It helps to ensure that connections remain stable even when the network is busy. For the applications mentioned, not only a low response time – the so-called latency – is crucial, but above all a constant, stable latency. Fluctuations in latency – known as jitter – affect the user experience.

How does L4S work?

In essence, the mobile network detects at an early stage when it is congested, before data is lost or delays occur.

Here's how it works:

1. The network detects an imminent overload:
   It marks certain data packets with so-called ECN bits (Explicit Congestion Notification) – a kind of "warning signal" that bottlenecks could occur.
2. Devices and servers respond to this warning:
   In gaming, for example, servers and end devices deliberately reduce the amount of data – e.g. by slightly reducing image quality – in order to maintain a stable connection.
3. This prevents queues and delays:
   Data continues to reach the user quickly and evenly – without stuttering, without dropouts. The fluctuations or jitter are low – the connection is stable.

Why can the mobile network be congested at all?

Mobile communications work according to the principle of a shared medium, i.e. a shared transmission path. This means that all users in a radio cell share the available bandwidth – like a piece of cake. The more people are online at the same time, the smaller the share for each individual becomes. If it gets too crowded, there is only a very small piece left for everyone – and you can feel that in the slower connection.

L4S and 5G Network Slicing: The Perfect Team for Real-Time Applications

L4S shows its full power in combination with 5G Network Slicing. In network slicing, the mobile network is divided into several virtual networks (so-called "slices") that are reserved for specific purposes – for example, for cloud gaming, teleoperated driving or industrial applications.

These slices can be equipped with additional functions and thus specially configured for specific applications. For example, for 5G+ gaming, the slice is configured with L4S, so that even with high network load, the cloud games benefit from particularly low latency and high stability - and thus run smoothly.

Who benefits from L4S?

L4S is particularly important for all applications where fast response times and stable connections are critical:

• Cloud Gaming 
• Video conferencing 
• Augmented Reality (AR) & Virtual Reality (VR)
• Remote control of vehicles (teleoperated driving)
• Real-time communication in industry

Our solution for gaming and more

L4S is recognized as a standard and has been included in 3GPP Release 18 for mobile networks. The function can thus be used with both current and future mobile communications standards. Deutsche Telekom has already integrated L4S into its 5G network – and is therefore ready for the requirements of tomorrow.

Learn more in the L4S Whitepaper.