Xperia 1 II loses 4G connection in Telenor Bulgaria's network

[peter_sl]

Hello,

I've been using Xperia 1 II (XQ-AT51) for about 3 months and I keep experiencing severe network issues with Bulgaria's Telenor mobile network operator. When I'm outside of urban areas, the handset shows it is connected to 4G, but when I try to use data it immediately disconnects and displays "No coverage" for a few seconds. Afterwards, it reconnects, but it only lasts until I attempt to use data again. This cycle continues infinitely, regardless of whether I'm moving or staying still. The preferred networks setting is set to 4G/3G/2G and if I change it to 3G/2G, I don't experience the problem. Other phones in the same area don't have any network issues. You can watch a screen recording of the handset's behaviour here.

And here comes the curious part: when I go to Software Info in the Service Menu (*#*#7378423#*#* > Service Info > Software Info) I see that the Current Modem Config is Telenor_Sweden.

This is totally incorrect in my opinion and probably has much to do with the network problems of the phone, because Telenor Bulgaria does not use the same set of 4G frequency bands as Telenor Sweden, which renders the handset unable to find the frequencies it expects. If I put a SIM card of another Bulgarian operator (A1, Bulsatcom) into the phone, the Current Modem Config changes to ROW_Commercial.

I'm reluctant to take this to a service center, because as I mentioned above, this happens only outside of urban areas, and will not be reproducible at all in the city where the service center is. I'd like to hear some opinions about my theory that the wrong modem configuration is causing the network issues, as well as how you think this can be corrected. I'm guessing it would need Sony to fix the software wrongly identifying Telenor Bulgaria's SIM card as Telenor Sweden one.

Thank you,

Petar

[BGXperia]

Having the same exact problem, Telenor BG network, keeps losing signal when switching 3G - 4G, cant really use the 4G network as it does it all the time. Any solution yet?

[peter_sl]

Sorry, no solution yet, but my contact at Sony Mobile Bulgaria informed me that they have opened an internal ticket about this, so we will have to wait and see. I expect it to be fixed in a future software update.

[Poseng1]

Let's hope they will get it fixed, because Samsung also have this problem with it's X55 modem

[peter_sl]

This is a really interesting discovery. It means that the modem comes bundled with carrier configurations from Qualcomm and it is them who ultimately have to fix it. Unfortunately, this also means that there is yet another party involved besides Sony Mobile, Telenor and whatever provider you are using. On the other hand though, if more phone brands are affected, the pressure on Qualcomm will rise a lot, especially because the new iPhones also use X55 

[peter_sl]

Just as I expected: iPhone 12 unexpectedly dropping LTE and 5G service for some users 

[Alibabahat]

Having same exact problem in Estonia with my Telia connection. 

I bought the phone 4 days ago and realised the sudden dropped WhatsApp call issues all came from my phone. 3G works perfectly but as soon as I switch to 4G or 5G the connection gets real unstable (tested with ping and noticeable).

Going to try take it back to shop and get another OnePlus I guess...

[peter_sl · Accepted solution]

I need a few more days to test, but for now it looks like updating to Android 11 has resolved the 4G network problem for me.

[Strampke]

Happy for you @peter_sl 

You needed a lot of patience.

Enjoy your device!

[BGXperia · Accepted solution]

It seems like I am no longer experiencing the problem, update has fixed it.

Now if there is something to be done with ear proximity sensor and everything would be flawless. Happy holidays, be safe, enjoy life

[math.el]

I've just upgraded to Android 11 yesterday (26.01.2021), but the issue still there. Hope to see a solution on Android 11.