Issue with sim latching and mqtt over sim through nrf9151

RE: Issue with sim latching and mqtt over sim through nrf9151

Vivek — Fri, 31 Oct 2025 10:10:49 GMT

It was a power issue causing the problem. Now it's resolved.

Thanks,

Vivek

RE: Issue with sim latching and mqtt over sim through nrf9151

Achim Kraus — Sun, 26 Oct 2025 18:37:21 GMT

[quote userid="78148" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151/552404"]Also as our main objective is to send data to server over mqtt using nrf9151, then will it work using either of LTE-M or NB-IoT? Is there any specific requirement from these two ?[/quote]

If you need to use TCP, especially with TLS, you may be more comfortable with LTE-M. In the "deep-building-penetration" the domain of NB-IoT, pretty larger RTTs will make TCP unhappy, that's then that domain of UDP (with CoAP/DTLS 1.2 CID).

[quote userid="78148" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151/552404"]received info that sim is activated for NB-IoT as the APN is set accordingly "jionpiot"[/quote]

that would then also explain, why it doesn't work with LTE-M only.

RE: Issue with sim latching and mqtt over sim through nrf9151

Vivek — Sun, 26 Oct 2025 15:47:10 GMT

[quote userid="5203" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151/552403"]According AT%XSYSTEMODE this is LTE-M and GNSS enabled, but not NB-IoT[/quote]

Ohh yes, I should make the 2nd parameter 1 for NB-IoT. I'll check it once and see if it makes any difference.

[quote userid="5203" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151/552403"]You need a SIM card with LTE-M/NB-IoT subscription, maybe your SIM doesn't have that.[/quote]

We checked with network provider and received info that sim is activated for NB-IoT as the APN is set accordingly "jionpiot"

[quote userid="5203" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151/552403"]You usually only able to read the signals once you're connected. But yes, if the SIM has a valid subscription, that may indicate an issue with your antenna[/quote]

That might be the issue but when we checked with nrf9160 DK we observed the same issue, so we couldn't doubt issue in our hardware.

Also as our main objective is to send data to server over mqtt using nrf9151, then will it work using either of LTE-M or NB-IoT? Is there any specific requirement from these two ?

Please suggest if there's anything else we can try and debug.

Thanks,

Vivek

RE: Issue with sim latching and mqtt over sim through nrf9151

Achim Kraus — Sun, 26 Oct 2025 12:25:47 GMT

[quote userid="78148" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151"]System mode: AT%XSYSTEMMODE=1,0,1,0 (LTE-M and NB-IoT enabled)[/quote]

According AT%XSYSTEMODE this is LTE-M and GNSS enabled, but not NB-IoT.

[quote userid="78148" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151"]Persistent registration failure: +CEREG: 5,4 (unknown/out of coverage)[/quote]

You need a SIM card with LTE-M/NB-IoT subscription, maybe your SIM doesn't have that.

[quote userid="78148" url="~/f/nordic-q-a/125214/issue-with-sim-latching-and-mqtt-over-sim-through-nrf9151"]No RF signal detected: +CESQ: 99,99,255,255,255,255 (all values indicate "not detectable")[/quote]

You usually only able to read the signals once you're connected. But yes, if the SIM has a valid subscription, that may indicate an issue with your antenna.