NRF9160 Cell Tower Blacklist

RE: NRF9160 Cell Tower Blacklist

Achim Kraus — Mon, 19 Dec 2022 07:31:45 GMT

> the device can send data over the same tower.

Great! That's good news. If single towers would have been a real world issue, then it would have been much more complicated.

> a reset is required.

Yep.

I decided to wait for the 1.3.4. Usually Nordic requests nrf9160 - sent udp message do not longer reach destination after 4 weeks traces, which is in such cases not too easy to provide.

RE: NRF9160 Cell Tower Blacklist

David — Mon, 19 Dec 2022 01:08:17 GMT

So upon further investigation it appears that the device can send data over the same tower.. however it does just stop working until a reboot is performed. even calling lte_lc_offline doesnt seem to work. a reset is required..

I have another device in the same area, however this is using a different tower and has been up and working pretty well. it goes offline occasionally but generally is pretty good.

RE: NRF9160 Cell Tower Blacklist

Achim Kraus — Fri, 16 Dec 2022 09:12:51 GMT

I'm just an other user, so hopefully you get also more qualified help.

Anyway, to make sure, your analysis is right, and the "rogue" tower is the culprit:

Did you try, what happens, it the modem starts with the "rogue" tower?

Or what happens, if you just restart the modem, but not the nRF9160 SoC ("lte_lc_offline()" and "lte_lc_normal()" again)?

Be very careful. "lte_lc_offline()" may result in storing the "rogue" tower as current and on restart using this one. If it's really the tower, then this may result in being "bricked". But it's hard to belief, that there are such "rogue" towers, using even the same PLMN.

(In my opinion there are several reports, that the modem sometimes have problems to "reconnect" and then send successful data. In my experience this still happens with the 1.3.3. I got reports, that the upcoming 1.3.4 will fix it. Crossing fingers.)