RE: nrf9160 : LTE connection issue

Hakon — Tue, 04 Oct 2022 12:28:15 GMT

Hello,

[quote user=""]1. What does RRC mode: connected mean ? Very often (even with Bell and Rogers) I see RRC mode: connected but then the connection attempt times out and lte_lc_init_and_connect returns -116 after 120 seconds.[/quote]

You can read about RRC states here. I'm not sure why the connection times out, but you can try to use the at client + link monitor to get more information, and also maybe a modem trace would be helpful.

[quote user=""]2. On many occassions i see LTE cell changed: Cell ID message even in RRC Idle mode. What causes this behavior? Is the modem trying to look for a better signal or connection? our device when idle will not send messages for a few hours but in between it will change cell towers many times while on PSM. How can I manage or disable this to not drain the battery prematurely?[/quote]

I don't think this is possible using LTE-M. For NB-IoT automatic handover is not possible, but it should not work with iBasis SIM, so you will need to use a different SIM in that case.

[quote user=""]3. What can I do to make the connection attempt faster, stable and reliable? Right now on a 10 minute connection cycle test (where I disconnect and reconnect every 10 minutes) sometimes I can connect within 5 seconds, at other time it will take 30-60 seconds, while occassionly it fails to connect. All of this while the device is on a desk and LTE signal stregnth is excellent in the office.[/quote]

The best way is probably with xbandlock. Also, the %xcountrydata cmd can be considered to decrease the time.

[quote user=""]4. Do newer SDKs (2.1) and the modem lib that comes with it improves the LTE connection? Will switching to newer SDK provide me any improvement on this aspect?[/quote]

Probably not. You would most likely need to upgrade the modem firmware to see any significant improvements to the LTE performance.