Showing posts with label Fixed Network. Show all posts
Showing posts with label Fixed Network. Show all posts

Thursday, 24 July 2025

L4S and the Future of Real-Time Performance in 5G and Beyond

As mobile networks continue to evolve to support increasingly immersive and responsive services, the importance of consistent low latency has never been greater. Whether it is cloud gaming, extended reality, remote machine operation or real-time collaboration, all these applications rely on the ability to react instantly to user input. The slightest delay can affect the user experience, making the role of the network even more critical.

While 5G has introduced major improvements in radio latency and overall throughput, many time-critical applications are still affected by a factor that is often overlooked - queuing delay. This occurs when packets build up in buffers before they are forwarded, creating spikes in delay and jitter. Traditional methods for congestion control, such as those based on packet loss, are too slow to react, especially in mobile environments where network conditions can change rapidly.

Low Latency, Low Loss and Scalable Throughput (L4S), is a new network innovation designed to tackle this challenge. It is an Internet protocol mechanism developed through the Internet Engineering Task Force, and has recently reached standardisation. L4S focuses on preventing queuing delays by marking packets early when congestion is building, instead of waiting until buffers overflow and packets are dropped. The key idea is to use explicit signals within the network to guide congestion control at the sender side.

Applications that support L4S are able to reduce their sending rate quickly when congestion starts to appear. This is done by using ECN, or Explicit Congestion Notification, which involves marking rather than dropping packets. The result is a smooth and continuous flow of data, where latency remains low and throughput remains high, even in changing network conditions.

One of the significant benefits of L4S is its ability to support a wide range of real-time services at scale. Ericsson highlights how edge-based applications such as cloud gaming, virtual reality and drone control need stable low-latency connections alongside high bitrates. While over-the-top approaches to congestion control may work for general streaming, they struggle in mobile environments. This is due to variability in channel quality and radio access delays, which can cause sudden spikes in latency. L4S provides a faster and more direct way to detect congestion within the radio network, enabling better performance for these time-sensitive applications.

To make this possible, mobile networks need to support L4S in a way that keeps its traffic separate from traditional data flows. This involves using dedicated queues for L4S traffic to ensure it is not delayed behind bulk data transfers. In 5G, this is implemented through dedicated quality-of-service flows, allowing network elements to detect and handle L4S traffic differently. For example, if a mobile user is playing a cloud-based game, the network can identify this traffic and place it on an L4S-optimised flow. This avoids interference from other applications, such as file downloads or video streaming.

Nokia's approach further explains how L4S enables fair sharing of bandwidth between classic and L4S traffic without compromising performance. A dual-queue system allows both types of traffic to coexist while preserving the low-latency characteristics of L4S. This is especially important in scenarios where both legacy and L4S-capable applications are in use. In simulations and trials, the L4S mechanism has shown the ability to maintain very low delay even when the link experiences sudden reductions in capacity, which is common in mobile and Wi-Fi networks.

One of the important aspects of L4S is that it requires support both from the application side and within the network. On the application side, rate adaptation based on L4S can be implemented within the app itself, often using modern transport protocols such as QUIC or TCP extensions. Many companies, including device makers and platform providers, are already trialling support for this approach.

Within the network, L4S depends on the ability of routers and radio access equipment to read and mark ECN bits correctly. In mobile networks, the radio access network is typically the key bottleneck where marking should take place. This ensures that congestion is detected at the right point in the path, allowing for quicker response and improved performance.

Although L4S is distinct from ultra-reliable low-latency communication, it can complement those use cases where guaranteed service is needed in controlled environments. What makes L4S more versatile is its scalability and suitability for open internet and large-scale public network use. It can work across both fixed and mobile access networks, providing a common framework for interactive services regardless of access technology.

With L4S in place, it becomes possible to offer new kinds of applications that were previously limited by latency constraints. This includes lighter and more wearable XR headsets that can offload processing to the cloud, or port automation systems that rely on remote control of heavy equipment. Even everyday experiences, such as video calls or online gaming, stand to benefit from a more responsive and stable network connection.

Ultimately, L4S offers a practical and forward-looking approach to delivering the consistent low latency needed for the next generation of digital experiences. By creating a tighter feedback loop between the network and the application, and by applying congestion signals in a more intelligent way, L4S helps unlock the full potential of 5G and future networks.

This introductory video by CableLabs is a good starting point for anyone willing to dig deeper in the topic. This LinkedIn post by Dean Bubley and the comments are also worth a read.

PS: Just noticed that T-Mobile USA have announced earlier this week that they are the first to unlock L4S in wireless . You can read their blog post here and a promotional video is available in the Tweet below ðŸ‘‡

Tuesday, 11 October 2022

The Role of Connectivity and Devices in Healthcare


Over the last few months I have discussed the role of 5G in different industries as part of various projects. Some of these discussions are part of my blog posts while others aren’t.

5G is often promoted as a panacea for all industries including healthcare. This presentation and video looks not only at 5G but other connectivity options that can be used to provide solutions for healthcare. In addition, this presentation looks at different components of the mobile network and explore the role of devices in healthcare.

Presentation and video below

You can download the slides here.

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Thursday, 4 March 2021

The Fifth Generation Fixed Network (F5G)


Back in Feb 2020, ETSI announced the launch of a new group dedicated to specifying the fifth generation of Fixed Network (ETSI ISG F5G). The press release said:

We are entering an exciting new era of communications, and fixed networks play an essential role in that evolution alongside and in cooperation with mobile networks. Building on previous generations of fixed networks, the 5th generation will address three main use cases, a full-fiber connection, enhanced fixed broadband and a guaranteed reliable experience.

For home scenarios, emerging services such as Cloud VR (virtual reality) and AR (augmented reality) video streaming or online gaming introduce the necessity for ultra-broadband, extremely low latency and zero packet loss. Business scenarios such as enterprise Cloudification, leased line, or POL (Passive Optical LAN) require high reliability and high security. Other industry sectors have specific requirements on the deployment of fiber infrastructures including environmental conditions such as humidity, temperature or electromagnetic interference.

The ETSI ISG F5G aims at studying the fixed-network evolution required to match and further enhance the benefits that 5G has brought to mobile networks and communications. It will define improvements with respect to previous solutions and the new characteristics of the fifth-generation fixed network. This opens up new opportunities by comprehensively applying fiber technology to various scenarios, turning the Fiber to the Home paradigm into Fiber to Everything Everywhere.

ISG F5G considers a wide range of technologies, and therefore seeks to actively cooperate with a number of relevant standardization groups as well as vertical industrial organizations. ISG F5G will address aspects relating to new ODN technologies (Optical Distribution Network), XG(S)-PON and Wi-Fi 6 enhancements, control plane and user plane separation, smart energy efficiency, end-to-end full-stack slicing, autonomous operation and management, synergy of Transport and Access Networks, and adaptation of the Transport Network, amongst others.

The five work items approved last week deal with:

  • F5G use cases: the use cases include services to consumers and enterprises and will be selected based on their impact in terms of new technical requirements identified.
  • Landscape of F5G technology and standards: this work will study technology requirements for F5G use cases, explore existing technologies, and perform the gap analysis.
  • Definition of fixed network generations: to evaluate the driving forces and the path of fixed network evolution, including transport, access and on-premises networks. It will also identify the principal characteristics demarcating different generations and define them.
  • Architecture of F5G: this will specify the end-to-end network architectures, features and related network devices/elements’ requirements for F5G, including on-premises, Access, IP and Transport Networks.
  • F5G quality of experience: to specify the end-to-end quality of experience (QoE) factors for new broadband services. It will analyze the general factors that impact service performance and identify the relevant QoE dimensions for each service.

Then in May, at Huawei Global Analyst Summit 2020 (#HAS2020), Huawei invited global optical industry leaders to discuss F5G Industry development and ecosystem construction, and launched the F5G global industry joint initiative to draw up a grand blueprint for the F5G era. The press conference video is as follows:

Then in September 2020, ETSI released a whitepaper, "The Fifth Generation Fixed Network: Bringing Fibre to Everywhere and Everything"

Now there are couple of standards available that provides more insights.

ETSI GR F5G 001 - Fifth Generation Fixed Network (F5G); F5G Generation Definition Release #1:

In the past, the lack of a clear fixed network generation definition has prevented a wider technology standards adoption and prevented the creation and use of global mass markets. The success of the mobile and cable networks deployments, supported by clear specifications related to particular technological generations, has shown how important this generation definition is.

The focus of the 5th generation fixed networks (F5G) specifications is on telecommunication networks which consist fully of optical fibre elements up to the connection serving locations (user, home, office, base station, etc.). That being said, the connection to some terminals can still be assisted with wireless technologies (for instance, Wi-Fi®).

The main assumption behind the present document foresees that, in the near future, all the fixed networks will adopt end-to-end fibre architectures: Fibre to Everywhere.

The present document addresses the history of fixed networks and summarizes their development paths and driving forces. The factors that influence the definition of fixed, cable and mobile network generations will be analysed. Based upon this, the business and technology characteristics of F5G will be considered.

This table comparing the different generations of fixed networks is interesting too


ETSI GR F5G 002 - Fifth Generation Fixed Network (F5G); F5G Use Cases Release #1:

The present document describes a first set of use cases to be enabled by the Fifth Generation Fixed Network (F5G). These use cases include services to consumers and enterprises as well as functionalities to optimize the management of the Fifth Generation Fixed Network. The use cases will be used as input to a gap analysis and a technology landscape study, aiming to extract technical requirements needed for their implementations. Fourteen use cases are selected based on their impact. The context and description of each use case are presented in the present document.


The use cases as described in the present document are driving the three dimensions of characteristics that are specified in the document on generation definitions [i.1], namely eFBB (enhanced Fixed BroadBand), FFC (Full-Fibre Connection), and GRE (Guaranteed Reliable Experience). Figure 2 shows that:

  • depending on the use case, one or more dimensions are particularly important, and
  • all dimensions of the F5G system architecture are needed to implement the use cases.

I will surely be adding more stuff as and when it is available.

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