Wednesday, 31 December 2025

Top 10 Posts for 2025

As we come to the end of another busy year, it is time once again to look back at what readers found most interesting on The 3G4G Blog. This year we again crossed over 3 million views, the same as last year, which shows the consistently strong interest in mobile technology, standards, and real-world deployments.

With well over 2,000 blog posts now published since the blog began in 2007, it is always fascinating to see which topics continue to attract attention. Some posts reflect the latest developments, while others are long-standing fundamentals that engineers, students, and professionals still search for regularly.

Regardless of when they were published, these were the top 10 most-read posts on the blog this year:

  1. 3GPP Release 18 Description and Summary of Work Items, Aug 2024
  2. 5G-Advanced Store and Forward (S&F): Enabling Resilient IoT Communications via Satellite, Apr 2025
  3. VoLTE Bearers, Aug 2013
  4. Difference between SDU and PDU, Mar 2009
  5. Network Slicing using User Equipment Route Selection Policy (URSP), Nov 2021
  6. LTE to 3G Handover Procedure and Signalling, Mar 2011
  7. Introduction to 5G ATSSS - Access Traffic Steering, Switching and Splitting, Nov 2019
  8. Interesting Pic: Blackberry Evolution, Jul 2010
  9. New 5G NTN Spectrum Bands in FR1 and FR2, May 2023
  10. What is RF Front-End (RFFE) and why is it so Important?, Jan 2022

It is interesting, although not entirely surprising, that a mix of 3GPP standards content, mobility procedures, and radio fundamentals continues to dominate the rankings. Posts written more than a decade ago still feature strongly, which highlights how many people continue to rely on them for reference and learning.

At the same time, more recent topics such as 3GPP Release 18, 5G-Advanced, and NTN show where industry activity and curiosity are heading as networks continue to evolve.

In addition to the 5G-Advanced Store and Forward (S&F) blog post, which was comfortably the most-read new post this year, the next most popular posts published in 2025 were:

  1. AI/ML in 3GPP: Progress, Challenges, and the Road to 6G, Mar 2025
  2. Understanding L1/L2 Triggered Mobility (LTM) Procedure in 3GPP Release 18, Aug 2025
  3. The Evolution of 3GPP 5G Network Slice and Service Types (SSTs), Jul 2025

AI and Machine Learning, mobility optimisation, and network slicing all remain strong areas of interest as the industry continues to mature 5G and look ahead to the next generation.

A big thank you to everyone who reads, comments, shares, and supports the blog. Whether you have been following since the early 3G days or discovered the site more recently, your continued engagement is what keeps it going.

Here is to another year of learning, sharing, and exploring the evolving world of mobile and wireless technology.

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Thursday, 18 December 2025

Transport Networks Holding Modern Mobile Architectures Together

When people talk about mobile networks, the conversation almost always starts with the air interface. Spectrum, waveforms, MIMO, antennas and radios dominate conference agendas, white papers and training courses. After that comes the RAN, then the core, and occasionally backhaul is given a brief mention. What sits quietly in the middle of all this, often taken for granted, is the transport network. Yet without a well designed transport layer, even the most advanced radio and core architecture struggles to deliver on its promises.

Transport networks are the connective tissue of mobile communications. They carry traffic between radio sites, aggregation layers, edge and regional data centres, and the core network. As highlighted in the accompanying Mpirical video, transport is not a single homogeneous network but an end to end topology made up of multiple architectural domains, each with different performance, scale and resilience requirements.

At the core of the network, transport is typically built using highly resilient designs such as full mesh or spine and leaf architectures. These environments are already operating at hundreds of gigabits per second per link, with clear evolution paths towards terabit scale throughput. This part of the network rarely gets attention from mobile engineers, yet it underpins everything that follows. If the core transport layer cannot scale, the rest of the mobile network inevitably hits a ceiling.

Moving closer to the cell site, the transport network transitions into metro and aggregation domains. Here, spine and leaf or ring based topologies are commonly used, supporting large numbers of high capacity connections while also providing access to edge and regional data centres. This is where transport starts to intersect directly with mobile architecture decisions. The placement of edge computing platforms, local breakout, and centralised RAN functions all depend on the capabilities of this aggregation layer.

Closer still to the access network, transport designs often shift again. Ring, star or chain topologies are frequently used to connect clusters of cell sites, with capacities that reflect both traffic demand and economic constraints. Although fibre is the dominant medium, especially for 5G, it is rarely the only one. Microwave, integrated access and backhaul, and even non terrestrial technologies play an increasingly important role in extending coverage and improving resilience where fibre is impractical or unavailable.

The importance of transport becomes even clearer when viewed through the lens of disaggregated RAN and cloud based architectures. With gNodeB functions split into remote radio units, distributed units and centralised units, transport is no longer just backhaul. It becomes fronthaul and midhaul as well, each with distinct latency, synchronisation and bandwidth requirements. Centralised units may sit deep in the network, served by high capacity backhaul, while distributed units are connected via midhaul rings and radios are attached using star or ring topologies at the very edge.

This architectural shift exposes a common blind spot. Many performance issues blamed on the RAN are in fact rooted in transport limitations. Synchronisation accuracy, latency variation and resilience all depend heavily on transport design and operation. Packet based transport, while flexible and cost effective, places strict demands on timing and quality that cannot be treated as an afterthought.

As networks move towards 5G standalone, private networks and early 6G concepts, transport will become even more tightly coupled with service delivery. Network slicing, deterministic performance and edge driven applications all rely on a transport layer that can offer predictable behaviour rather than best effort connectivity. This pushes transport out of the shadows and into the critical path of mobile network design.

The 5G Transport Network Topology video as follows:

For mobile engineers, the message is clear. Understanding the air interface will always be essential, but it is no longer enough. Transport networks shape where functions can be placed, how services perform, and how networks scale over time. The video embedded alongside this post provides a useful visual reminder that mobile networks are not just radios and cores connected by invisible links. Transport is a network in its own right, and it deserves far more attention than it usually gets.

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