Phone App kills mobile data connection

REPRODUCIBILITY (% or how often): Every time after receiving a call
BUILD ID = OS VERSION (Settings > About product):
HARDWARE (XA2, Xperia 10…): Xperia 10 Dual SIM
REGRESSION: (compared to previous public release: Yes, No, ?): Since update to SFOS 4


After every received call the mobile data connection is broken. If the phone is connected to Wi-Fi then all works fine. The problem appears at mobile data only connection. I have to restart the whole phone to bring the data connection up again.






(Please ALWAYS attach relevant data such as logs, screenshots, etc…)

Is the mobile data connection via a 4G network when the call begins?


Yes, always connected via 4G. Phone carrier is T-Mobile Germany.

This is most probably related to the fact that the GSM generation 4G is lacking dedicated voice channels (in contrast to 3G and 2G). Therefore, voice calls in 4G network require the “voice over IP” technology (sometimes called voice over LTE or VoLTE).

Because Sailfish OS does not (yet) support VoLTE, the connection to the cellular network must be switched to a 3G (or 2G) one for phones calls. Obviously, this pauses the ongoing 4G data connection when a call is started.

But it only pauses, it should not terminate. I tried this (again) with my XA2 and 10 phones having the SIM cards of Telia and Elisa (2 of the 3 main operators/carriers in Finland) and indeed, the phones returned from 3G to 4G and the playback of Youtube videos (played with Sailfish Browser) was automatically continued when my test calls ended.

I wonder if the network of your carrier works in a bit different way.

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Thanks for the explanation. Here in Germany we also had only 3 remaining carrier vendors. T-Mobile, Vodafone and O2 (the former EPlus).

Today I had three calls with the phone and at first all was working well. No problems with the mobile data connection at two calls. The third one knocks out the data connection again. It seems to be a carrier problem, but I’m not sure about. :frowning: