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Germany is preparing to use cell broadcast messages for emergency warnings issued by the government. A first country-wide test is planned for December 8, 2022 as part of the Nationwide Alert Day 2022.

Many publications claim that reception of these cell broadcast messages will only work under Android 11 or newer:

However, as far as I understand, the underlying technical standard is about 20 years old, and Android has supported cell broadcast for ages (since at least Jelly Bean / V4.1, release 2012).

So why should there be a problem with Android versions before 11?

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2 Answers 2

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I'll try to answer my own question :-)

tl;dr

This seems to be a misunderstanding. With Android 11 or later, cell broadcast messages for emergency warnings are pretty much guaranteed to work, but they work on many devices with older versions, too.


Source of the claim

This claim seems to be based on a misunderstanding - probably some press release that got misquoted or incorrectly abbreviated somewhere along the line.

It is unclear where this claim originated. Many news sources have published it (see links in question), but the sources I found all do not attribute the claim, and use similar wording, so they probably copied it from some press release or article somewhere. The official site of the responsible German government agency (Bundesamt für Bevölkerungsschutz und Katastrophenhilfe - https://www.bbk.bund.de/ ) does not mention Android 11 specifically - instead, it lists individual phone models that are or are not supported (Kann mein Gerät Cell Broadcast empfangen?).

Technical details

  • Each Cell Broadcast message contains a "message identifier" or "message ID" (also called a "channel" on some phones), a number from 0-65535. That message identifier tells the phone the type and content of the message, such as a weather report, a technical message, or a warning message.
  • For emergency warnings, specific message IDs have been reserved for different types of warnings, in particular IDs 4352 – 6399. The technology, along with the message IDs, is contained in the standard ETSI TS 123 041, at least since version 9.2.0, published in January 2010. The new German warning system, specified in the offical standard Technische Richtlinie DE-Alert, basically follows this standard.
  • Support for emergency warnings via Cell Broadcast mainly requires that the phone reacts to Cell Broadcast messages with these message IDs. The offical Android source code has supported these emergency warning message IDs since at least V4.2/Jelly Bean (see source code).

Conclusion

The offical Android source code (as published by the Android Open Source Project) has supported cell broadcast emergency warnings with the standardized message IDs since at least V4.2/Jelly Bean, so in principle emergency warnings should work at least with all phones running Jelly Bean or later..

However, phone manufacturers (and even mobile network operators supplying phones to customers) can and do customize the official Android source code they put on their devices. It is possible that some of them removed or deactivated warning messages, either entirely, or specifically for German phone networks, as these warnings were not previously used in Germany. For example, on older Samsung phones warnings are supported, but must be manually activated (offical Samsung page).

This changed with Android 11. Before, emergency warning support was part of the general source code, which manufacturers modify and ship to end users. In Android 11, a new Cell Broadcast module was introduced. While the actual functionality seems mostly unchanged, the new module can be updated individually by Google via OTA updates (specifically as an APEX package). That means Google can push updates without requiring a complete Android OS update, and independently of the manufacturers (who may not want to provide updates for old phones).

That means that phones which

  • run Android 11 or later, and
  • are up to date with Google updates

are practically guaranteed to support emergency warnings, as Google has provided a suitable update. However, many phones running Android 4.2 or later also support these warnings.

Check settings

To see if your device supports warning messages, check Android settings, or the message app settings (depending on device). If the configuration is available in the settings (look for a section called "emergency alerts" or "wireless emergency alerts"), and if the alerts are activated there, the phone will most likely support the warnings (unless the manufacturer made complicated changes, which is possible but unlikely).

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    You can find the Message-IDs for CMAS / EU-Alert Level 1-3 even in the source for Android 2.3.6. CellBroadcast warnings might also be supported if the option is nowhere in the settings. The OEM might just have removed/forgotten the link. The App "Activity Launcher" can still find the settings if you search for "cellbroadcast".
    – xsrf
    Dec 17, 2022 at 20:22
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That's not an easy to answer question. According to reporting Germany extended the GSM standard that already was provided by most mobile phone vendors, by insisting on a message-identifier length of four instead of three digits. Germany formerly relied on a bunch of apps like

  • NINA
  • BIWAPP
  • Katwarn

to only name the best known ones. Neither of them were widespread enough to provide propper warnings for all citizens, nevertheless the Bundesamt für Bevölkerungsschutz und Katastrophenhilfe (BBK) pushed for these apps instead of an app-independent solution so much that some vendors even removed the CBS functionality completely if the device ought to be sold in Germany (my LG for example does not provide it). This would be another obstacle to overcome now anyways.

Interestingly enough does section 9.4.1.2.2 of TS 123 041 specify the four digit message-identfier 4370 to 4393 used by DE-Alert even in version V11.4.0 of 2012 for PWS/EU-Alert. So why this shouldn't be implemented in most phones for years, I don't understand. Perhaps I have misread the whole thing but for me it represents as a lack of pressure from other countries to implement the standard. Additionally, as the working group for critical infrastructure (AG Kritis) in Germany states: the practice (in other countries) in the past were three digit message-identifier (reserved for operator messages according to TS 123 041). But the BBK amended it's requirements in a way that older devices would also receive a message-id 919 in parallel for highest severity, unfortunately they did this too late for other providers than T-Mobile to comply before alert day was due.


TL;DR: Other countries used existing functionality in phones to implement PWS while Germany relied on apps for years. Which is the reason they decided to drop backward functionality for older phones until it was too late for the test on alert day.

Sources:

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  • Yes, the three-vs-four digit thing was mentioned in other articles as well. However, as far as I could find, that is not the real problem - as you write, four-digit message identifiers were already specified in TS 123 041 back in ~2010, so every phone from that last ten years should support them. The problem is only with very old phones (20+ years).
    – sleske
    Dec 16, 2022 at 8:12
  • I assume that the cell broadcast message id which has a limit in former implementations is not the message id that the standards talk about. Because it's a fact that during alert day older mobile phones were not working, even though they'd support CBS in other countries. Now that you've answered your question yourself, I see that the question actually wasn't "Why should there be a problem with Android versions before 11?", because your analysis seems to be that there is no problem. I trust the analysis of AG Kritis more than yours, though. I'm just missing the origin of the id length issue.
    – HJo
    Dec 19, 2022 at 7:52

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