Uncategorized – Page 16

EU-Alert – Will It Stop Alerting Eventually?

Recently, two federal states in Germany tested their EU-Alerting System implementation. Based on the cell broadcast mechanism that exists in all 3GPP network technologies since the the days of GSM, it makes phones emit a loud warning signal and shows a message on the screen. It definitely does wake one up, as I already discovered in 2016 in the Netherlands when they had one of their regular test runs of their system.

So while one is inclined to confirm and thus silence the alert as quickly as possible, I wondered if it would eventually stop on its own. Why? Well, every now and then I do have a phone lying around at home while I’m not there. It would be pretty unfair to the neighbors if it kept alerting indefinitely. So I collected a number of different phones and didn’t touch them once the alerts got going. And indeed, after 5 minutes, they all dropped silent simultaneously. Good for the neighbors!

Does SPF make Google Mail Happier?

In our household we mostly use Ionos (formerly 1&1) for forwarding our email correspondence. While I personally had little to no issues so far with dropped emails due to spam filters of Google, Microsoft, etc., other members of the household were not so lucky recently. The main problem of emails erroneously dropped by spam filters is that there is no way of knowing that this has happened until people tell you that they haven’t received an email. Since I’m not affected, I was wondering why it happened to other family members recently more than once, and what could potentially be done about it.

NTN – Part 6 – Satellite Mobility

In the previous episodes, I’ve gone into some of the details of the Non-Terrestrial Network (NTN) extensions specified in 3GPP Rel. 17 36.300 and 38.300. One main aspect I haven’t addressed so far is mobility, so let’s have a look at that today! Actually, mobility in NTN is even more fun than in terrestrial networks because it’s not only the mobile device but also ‘the network’ that can potentially move from one place to another!

A First Test of Whisper AI

While the press and pretty much everybody focuses on ChatGPT these days, there’s another project of the same company that was recently open sourced that promises to create transcripts of video and audio files. It’s called Whisper AI. As I do get audio files every now and then for which a transcript would be helpful, I installed a local instance and gave it try.

NTN – Part 5 – Why Does the UE Need a GPS Fix?

And again a seamless continuation from part 4 on 3GPP’s Non-Terrestrial Networks specification extension in Release 17 in which I’d like to come back to a particular requirement: The mobile device has to be aware of its location, which means it has to get a GPS fix before it can contact the network via a satellite. This is an interesting and quite ‘uncommon’ requirement compared to how satellite communication works today. 3GPP describes this as follows in TS 36.300:

NTN – Part 4 – Satellite and Mobile Operator Mix and Match

This part is the seamless continuation of part 3 on the 3GPP TS 36.300 and TS 38.300 extension for Non-Terrestrial Networks, i.e. satellite communication. So let’s jump back straight in. Before we talk more about specific architecture options, here are two more terms used in the specification that are important to understand:

As discussed in the previous posts, the satellite acts as a ‘bent-pipe’ repeater in the 3GPP specifications for satellite communication, and the eNodeB / gNodeB base station is on the ground. This means that instead of a direct link between a mobile device and the base station, there are now two legs in the connection: First, there’s the radio link between the mobile device and the satellite, which is referred to in the specifications as the ‘service link‘. And then, there’s the link between the satellite and the base station on the ground, which is referred to as the ‘feeder link‘. As the satellite is ‘only’ a repeater from an overall system point of view, both links carry the same radio signal. However, it is possible that the service link and feeder link use different frequency bands, i.e. the repeater in space (the NTN payload, see previous post) must be able to change the carrier wave frequency of the signal.

That being said, lets have a look at the different NTN network architecture options specified by 3GPP:

Reality Bites – Flight Simulation – Part 7 – SimBrief and Navigraph

When flying with Visual Flight Rules (VFR) in the simulator, I’ve come to rely on SkyDemon, a real world tool to plan VFR flights and then use it during the virtual flight to find my way and to avoid ‘Charlie’ airspace and restricted areas. When flying with Instrument Flight Rules (IFR), other real life tools such as ForeFlight are an interesting option to use in the simulator. However, ‘the Internet’ seems to conclude that the combination of SimBrief and Navigraph for flight planning and flying is a better alternative for the simulator. I was a bit skeptical at first, because I want my simulator flying as close as possible to the real world, but I gave it a try anyway. So here’s how that went:

NTN – Part 3 – 3GPP Rel. 17 – System Architecture for Satellite Services

In part 1 of this series, I’ve taken a high level look at how the LTE and 5G air interface specifications have been extended in 3GPP Release 17 to accommodate for weaker signals, longer delays and patchy coverage typically experienced over satellite. In part 2, I’ve chased the question why the LTE NB-IoT and CAT-M in particular have been extended and which features they have that are also very useful if a smartphone or other mobile device communicates via a satellite. In this part, I’ll now have a closer look how the overall 3GPP LTE and 5G System Architecture has been enhanced in 3GPP Release 17 for use with Non-Terrestrial Networks (NTN).

When All Else Fails – The Garmin InReach Mini 2 – Part 12 – Capacity for InReach

Wow, this is already part 12 in my blog series on the Garmin InReach Mini 2 and the underlying Iridium satellite constellation. Perhaps you remember, my main use case for the Mini 2 is to have a means to communicate with family members in other countries should there be a longer network outage, be it local or more widespread. While the service works great during normal times, I wonder of course if and how quickly Iridium would get overloaded, should there be a widespread terrestrial network outage. So I made a number of assumptions to chase the answer, or to get at least a basic feeling for this.

NTN Part 2 – NB-IoT over Satellite

In the previous post on the topic, I’ve been looking at how 3GPP has studied and then extended the LTE and 5G NR air interface so it can be used over a satellite link. For transmitting data to and from smartphones with omnidirectional antennas over satellites, 3GPP has extended the LTE Narrowband Internet of Things (NB-IoT) air interface. But why a narrowband technology for Internet of Things applications, all the hype is around satellite connectivity for smartphones these days!? Thanks to the experience gained with my Garmin InReach Mini 2, I think I have a pretty good idea why. So let’s have a look at the limitations of a satellite link to small mobile devices and which nifty features that are part of terrestrial NB-IoT can also be very useful for this type of satellite communication.