WiFi Hotspot makes network switching much less reliable

REPRODUCIBILITY: 75% (often)
OSVERSION: 4.4.0.72
HARDWARE: Sony Xperia 10 III - xqbt52 - xqbt52 - 1.0.0.176 - aarch64
UI LANGUAGE: Polski (user: pl_PL, os: pl_PL.utf8)
REGRESSION: no

DESCRIPTION:

I went back to travelling, which made me realised that network switching behaviour is much different when hotspot is enabled or not. By default, network switching on SFOS is a bit rough, but good enough.
But when I enable hotspot and move enough it will have to switch networks a few time, I will end up with it uses using 3G, no matter how good 4G range is and how bad 3G is. At least after disabling hotspot it will switch to 4G after a while.
What is more annoying, is when sometimes it gets stuck on 3G without data transfer, and then only way to fix it is to reboot the phone.
This behaviour happens to be every time I drive a bus or a train, sometimes it takes an hour, sometimes 20minutes. Happens even sometimes when I am stationary.
Is ofono’s behaviour different when hotspot is on or off? Could it be changed back to stock, as it is much more reliable?

PRECONDITIONS:

STEPS TO REPRODUCE:

  1. Turn on WiFi Hotspot
  2. Drive a car or bus, where the phone has to switch between 4G and 3G a few times, or just go through a place with weak signal
  3. Soon it gets stuck on 3G, and if you disable hotspot sometimes it will go back ti 4G after a few seconds
  4. Sometimes though, it will get stuck on 3G but with no data transfer. Then even if I disable hotspot, it will still stay stuck like that, with no data and 3G
  5. If I turn on airplane on, or swtich to 3G preference and then back to 4G preference, or even restart ofono it will connect to 4G for a second, and then switch back to 3G, still without data.

EXPECTED RESULTS:

ACTUAL RESULTS:

MODIFICATIONS:

  • Patchmanager: yes
  • OpenRepos: yes
  • Chum: yes
  • Other: yes:
    MicroG and a lot of Android apps

ADDITIONAL INFORMATION:

Device Owner User: defaultuser
Home Encryption: enabled


the initial version of this bug report was created using Bugger 0.9.8+git1

Presumably the switch back to 4G happens only after some time of inactivity; and having something connected to the hotspot makes it so that it can’t (as identified in 3.).

Remember that it is the network that makes the decisions for you when you are connected.
I.e. i can’t really see that this is a SFOS bug (no, not even the 4. or 5. parts either, weird as they are).