CREG 3 and 9 at the same time?


I am very confused with my Raspberry Pi Cellular IoT Kit (ME910C1-WW) when using NB-IOT. Actually, it is working as at+cereg? is returning +CEREG: 2,5,"BEBD","148C366",9. But not all the time. Sometimes it returns +CREG: 0,3. But why should my access be denied if I can connect 10 sec before and after? To make matters even more weird: when calling systemctl status ppp_connection_manager.service it reports all the time +CREG: 0,3, but at the same time at+cereg? returns status 9!

Is there another interpretation of +CREG: 0,3? Could it be also coverage related? Or is it a reboot loop?

Btw., how is ppp_connection_manager.service related to sudo pon? Should I use it in combination or either the one or the other?

Is it normal, that I can ping all the time via ppp0 device. I am surprised that some pings are relatively quick. Can I be sure that they are not going out via GSM (I’ve set at+ws46=28!)?

ping -I ppp0 -c 5

PING ( from ppp0: 56(84) bytes of data.

64 bytes from ( icmp_seq=1 ttl=56 time=158 ms

64 bytes from ( icmp_seq=2 ttl=56 time=1319 ms

64 bytes from ( icmp_seq=3 ttl=56 time=376 ms

64 bytes from ( icmp_seq=4 ttl=56 time=3156 ms

64 bytes from ( icmp_seq=5 ttl=56 time=2138 ms

I am also surprised, why the module knows all the time its registration status? Isn’t it supposed to be sleep all the time? Or do my commands constantly wake it up? I couldn’t find much documentation either about Long-Periodic TAU. Can it be configured?

I’ve setup my module on a raspberry pi 4 with latest Raspberry OS (32 Bit, 2022-09-22, lite). I followed the procedure by the documentation. The module is created via USB, I’ve created accordingly a PPP device. NB-IoT is manually enabled via atcom:




+CEREG: 2,5,`BEBD","148C366",9

It would be great if someone give me some hints!