Emergency! Dinner is ready!

I’m not a parent myself but I was a teenager once. Looking back at that time it must have been quite annoying for my mom to deal with me. Not only did I always want to eat Schnitzel for dinner, but she also had a hard time getting me to the table when dinner was ready (especially when there were veggies on the menu). I remember she even called me a couple of times on my landline (yes, I am that old).

So how to deal with a grumpy teenager? What if, instead of shouting through the whole apartment, you simply send an alert to the smartphone of your kids whenever you want to notify them. And we are not talking about a simple WhatsApp message they can just ignore or mute. No, a real emergency alert which you actively need to discard, and which is so loud it will make you fall from your chair if it catches you by surprise.

Don’t look any further! 5G-MAG (short for 5G Media Action Group not 5G Mother Action Group) has you covered. All you need is an Ubuntu System, a Software-Defined Radio (SDR), a CRD device listening on a specific frequency and the transmitter (base station) that can be found in the 5G-MAG Reference Tools . Easy right? This is how our setup looks on a high level:

The Ubuntu 22 machine is running our 5G-MAG transmitter sending SIB12 messages via the BladeRF SDR and an antenna to our CRD device. The device itself handles the reception and the rendering of the emergency alert. Now let’s investigate the individual steps:

SIB your mouth

Twelve is not only a nasty age (I assume no twelve-year-old is reading this, so sorry to everyone who has a kid of that age) but it is also a magic number in terms of the messages we need to send. SIB12 messages (short for “System Information Block”) are messages transmitted by the base station to convey warnings of an emergency nature to mobile devices. Typically, this includes critical information such as natural disaster alerts like tsunami or earthquake warnings.

Our 5G-MAG Transmitter based on srsRAN is able to transmit such SIB12 messages. To make the transmitter work we need an SDR with an antenna connected to an Ubuntu machine.

Blade – The frequency slayer

There is a wide set of SDR systems available on the market. For our purposes we chose the BladeRF. Not only does it provide the required features it is also affordable and has one of the coolest names.

Below you can see my BladeRF with an antenna connected to the TX1 port. The USB cable connects our BladeRF to the Ubuntu machine that is running the 5G-MAG Transmitter.

I feel we are on the same wavelength

Now that we have all components in place to transmit our emergency alerts we can focus on the receiving end. For our demo purposes, we do not want to connect to a mobile network but simply receive the alerts and show them on the screen. For that reason, we need a special device. One that can operate in receive-only mode and is tuned to the frequency that we are sending our SIB12 messages on. Luckily, we know a guy who knows a guy who knows a guy…you know! So, we were lucky enough to get a “Commercial Research Device (CRD)” that can operate in exactly that way. It looks suspiciously like a “normal” smartphone:

The emergency alerts are handled natively by the underlying Android operating system and do not require a dedicated application.

The final act

Without further ado. This is how our final demo looks like (sorry for flinching, the sound got me again):

Reproducing the setup

Now if you want to try this out yourself we have prepared a detailed and more technical tutorial including the required configuration on our website. I recommend not holding a cup of coffee in your hand when you trigger the alert though.


The author would like to congratulate Klaus Kuehnhammer (Bitstem), Jordi Gimenez (5G-MAG), Jaime Sánchez Roldán (UPV) and all the other contributors of the 5G-MAG Reference Tools for their work on this project.

Meet us in Berlin

Klaus Kuehnhammer, Jordi Gimenez and many more of the 5G-MAG Reference Tools community are joining us in Berlin on June 11–12 2024 for the 11th FOKUS Media Web Symposium. Learn more about the event and how you can register here.

If you want to learn more about our 5G and 6G activities checkout our website.

Leave a Reply

Your email address will not be published. Required fields are marked *