Unreliable mobile data connection on Samsung Galaxy Note 3 LTE (hlte)

I recently installed /e/OS R 0.18 on Samsung Galaxy Note 3 LTE (hlte) and I’m very pleased overall.

Mobile data connection is unreliable, however. I haven’t found this reported in the forums or in GitLab.

  • Device model is SM-N9005
  • /e/OS version is 0.18-r-20211003138753-dev-hlte
  • SIM card works fine and is 4G
  • Settings → About phone → SIM status says voice and data network type is 4G; home network, not roaming
  • I’ve double checked APN settings and they are all exactly as recommended by the mobile operator

Turning mobile data off then on: often nothing happens; no H, H+ or 4G symbol; and browser reports no connection.

Changing preferred network type: the list has 34 permutations and combinations of LTE, NR, WCDMA, GSM, etc. I’ve tried about half of them. Sometimes changing the preferred type and waiting ~30 seconds enables H, H+ or 4G icon. Often it makes no difference.

Sometimes, tweaking the APN settings triggers something. For example, if I change the MMC port number then change it back, the mobile data connection could be enabled. Then it disappears after a while.

I’m getting the same behaviour both at home (mediocre signal) and at work (excellent signal, close to a 4G/5G mast).

When mobile data connection somehow is enabled, the speed is very good and there are no transfer errors (that I can observe). No problems making voice calls or sending or receiving SMS. No problems with wifi.

I bought the phone “as new, unopened” a couple weeks ago. I didn’t use the stock ROM long enough to try mobile data, and I don’t have a copy of the stock ROM to try and confirm the hardware is OK.

Today, I could trigger a 4G data connection by changing the CDMA roaming mode from automatic to Home only. Changing it back to automatic has kept the 4G connection enabled.

A separate issue is, if I try to disable “Automatically select network”, the settings app hangs for two minutes while (I assume) trying to list available networks, then reverts to automatic.

About two hours later, 4G data connection dropped. Maybe there is a timeout when the connection is idle? I didn’t make any use of it. However, I also didn’t disable mobile data and the toggle is still enabled. Changing CDMA roaming mode does not re-enable the connection. This time, tweaking the APN settings triggers 4G connection.

4G data connection dropped after a couple hours.

The following day, I could re-enable it by changing the MMSC port number, wait a few seconds, then change it back. Mobile data connection symbol was first H, then 4G. Changing the preferred network type or CDMA roaming mode had no effect this time. Neither did disabling and enabling mobile data. Tweaking the APN settings seems to be the most reliable workaround.

I updated to 0.22-20220225165877 via OTA. After the successful update, I enabled 4G and the connection has been stable for over 14 hours. The bug must have been fixed somewhere between 0.18 and 0.22.