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When network operators are ready to go beyond 5G EN-DC, which basically means that a mobile device camps on a 4G cell and a 5G cell is added for additional speed, they require a 5G core network. To find out more about the 5GC, a good starting points are 3GPP TS 23.501 (System Architecture – Stage 2), followed by 23.502 (5G Procedures – Stage 2) and 24.501 (5G NAS Protocol – Stage 3). That’s quite a lot of ground to cover and while going over them I took some notes of things that I found of particular interest. This and the following blog posts are based on these notes and perhaps invite to investigate further.

Continue reading The 5G Core Network (5GC) – Part 1 – Network Entities

If you want to humble yourself as a VoLTE engineer at a point in time when you think you have more or less understood how VoLTE works, make a trace of a VoLTE conference call with a few participants and try to analyze that. You get back down to earth pretty quickly as complexity of conference calls in IMS VoLTE is staggering. But don’t despair, here are two tips how to figure this out:

Continue reading VoLTE Conference Calls – The Telco Engineer’s Darling!

There are lots of good books out there about the beginnings of the Internet in the 1960s and how people started using it in the decades to come. I specifically recommend ‘Dealers of Lightning‘ if you are interested in the early history. But how was the development of ‘networking’ in general and the ‘Internet’ in particular viewed from the outside starting in the 1970s?

Continue reading The Beginnings of The Internet From A German Perspective

If you go by 3GPP and common sense it can be expected that most operators having an LTE network today will launch 5G as what is referred to as 5G EN-DC (eUTRAN New Radio – Dual Connectivity), a.k.a. 5G NR ‘option 3’ in 3GPP circles. In other words, mobile devices will still camp on the existing 4G LTE eNB base stations and 5G gNB resources will be added when required. This makes sense in many cases as 5G will often be deployed on higher frequency bands and also not everywhere at first. Hence, the idea is to use the LTE network as a coverage layer and add 5G to the connection when available. Also, this has the advantage that no 5G core network (5GC) is required at first. But where do we go from here as 5G coverage gets more widespread and operators start using a 5G core network in addition to the existing 4G EPC?

Continue reading What Comes After 5G EN-DC?

I’ve been using virtualization on my notebook and in the cloud for many years now on a daily basis and as all of it has so far been on x86 based platforms so I was a bit surprised when I read about Virtualization on ARM last year in this Ericsson research paper. On second thought I should not have been, though, as virtualization is obviously a generic concept not tied to a specific processor architecture.

Continue reading Virtualization on ARM Processors

758k views and a decade later I must be one of the few who have not yet seen and heard the video of the song about “The Day The Routers Died” from the RIPE 55 meeting back in 2007. Back then, public IPv4 address depletion was already a big topic and sets the state for the song. If you also haven’t seen it yet, head over and cheer up!

When I recently traveled on a high speed train in France to the coast I experienced what the ‘digital divide’ really means. For the first one and a half hours of the trip on the 350 km long TGV line from Paris to Rennes, LTE coverage along the route was excellent. I don’t know if the train had on-board RF signal repeaters but since the signal was usually excellent I suspect so. Not only was the signal coverage good but I also managed to get quite some work done with web based services at 300 km/h. Upload and Download data rates were in the region of several megabits a second and I didn’t notice coverage holes that would have impeded with my work. That’s how it should be.

Continue reading The Digital Divide Starts in Rennes

When recently an rsync backup failed due to a full destination drive I had a closer look at the ext4 formatted partition and noticed that despite the disk being reported as full, 50 GB were unused. While this was not the reason for rsync to fail, I nevertheless wanted the 50 GB back.

Continue reading Where Did those 50 GB Go On My Backup Drive?

In the previous post I looked at 3GPP TS 23.401 and how the UE, the RAN and the LTE core network signal their 5G capabilities. TS 23.401 states that the LTE eNodeB signals a locally connected 5G gNB to the UE. But how does it actually do that?

Continue reading How Does An LTE eNB Signal A Co-Located 5G Cell?

In many cases 5G will come to smartphones, tablets and other devices in the form of 4G-5G dual-connectivity, also referred to as EN-DC (E-UTRAN New Radio – Dual Connectivity). While the mobile is in Idle state it will camp on a 4G LTE cell. A 5G NR cell is only added by the network once the device enters the RRC Connected state. Interesting conundrums that now present itself are for example if and how the mobile device can indicate to the user that it is ‘connected’ to 5G even while in Idle state and thus only really connected to a 4G cell!? Also, how does an LTE eNodeB know whether a 5G NR cell should be added when a mobile transfers to RRC connected state!? After all, network operators could decide that not all of their subscribers should have access to 5G. These problems do not exist today as the situation that a device talks to more than just one RAT (Radio Access Technology) is new. Some answers can now be found in the LTE core network specification 3GPP TS 23.401.

Continue reading LTE Core Network Enhancements for 5G EN-DC