My Ubuntu Touch devices participated in Thailand nationwide cell broadcast test

peat_psuwit

On 20 January 2025, Thailand government conducted a nationwide cell broadcast test. I've put my Ubuntu Touch devices to the test, and here are test results:

This requires some explanation:

MR 34 refers to ofono-sailfish!34 which fixes how oFono dumps the raw CBS SMS from the network in case oFono fails to decode it.
"Broad topic subscription" refers to me setting the subscribed topics beyond what is possible in Ubuntu Touch UI. Ubuntu Touch UI uses a hardcoded subset of CB topics, which does not include all topics I know exists for Thailand. More importantly, it does not include topic 4370 (National Alert) which supposedly should be always enabled.
"Msg info" is pulled from my Android phone running Android 16, designated as the reference device which should always receive this CB.
My Volla Phone 22 have a non-Thai SIM in it, and my Volla Phone X23 have a non-Thai and expired SIM in it. That's because that's all SIM I own...

There are a few notable things in this result:

Interestingly, even though Fairphone 5 does not have "4370" topic subscribed in oFono, it still receives a broadcast with topic "4370". This may indicates that FP5's firmware does always subscribe to topic 4370.
On the other hand, Volla Phone 22 which also does not have "4370" topic subscribed, does not receive the broadcast. Although, the SIM card I have in this device is actually a non-Thai one. So it's not clear if this device doesn't not receive a broadcast because the topic was not subscribed or because the device is in roaming mode.
- In theory. roaming-ness should not affect the ability to receive broadcast. In practice, I don't know.
- In hindsight, I should have swapped my Volla Phone Quintus to not have "broad topic subscription" and put it on my Volla Phone 22 instead, so it's clear what failure mode affects it.
On both devices that does not receive broadcast, I do not see an indication in the log that it has received a broadcast but cannot decode it.

I still maintain that we'll need a CB topic database from e.g. Android and should not not rely on hardcoded set of topics from a non-regional specification. Unfortunately, the test today is inconclusive on whether we need to explicitly subscribe to topic "4370" or not.

That's it for today. I'll continue to watch the news and be prepared when the next round of testing happens.

klh

@peat_psuwit do you have a spec for the Thai EBS? Looks like they require a working SIM card?

I still maintain that we'll need a CB topic database from e.g. Android and should not not rely on hardcoded set of topics from a non-regional specification.

In theory we should only need the table from 9.4.1.2.2 of 3GPP TS 23.041.

Unfortunately, the test today is inconclusive on whether we need to explicitly subscribe to topic "4370" or not.

We don't already? According to the same table, 4370 is not supposed to be settable by the user and always subscribed (I'm kind of extending the 3GPP definition of MMI here) so this shouldn't be a question - since afaik it's not required to be implemented at modem level, we should check what ofono reports and subscribe to the missing ones.

alagirialagiri

Please correct as 20, January, 2026 instead of 2025.Also,my android device sounds the test alarm but not my Ubuntu touch devices.How to enable them.