Issues registering in network when changing from one operator to another

[Aleksander Morgado]

Hey,

>> > I am developing an application making use of libmm-glib high level API and I am using a EM7455 Sierra Wireless modem. The modem is working under MBIM mode (usb-composition).
>> >
>> > I believe the issue I am experiencing is related to the change of operator / SIM card. The scenario is the following:
>> >
>> > The first SIM card I introduce is able to register in the network and connect using the APN I specify in order to establish a connection.
>> > I tell the modem to change the SIM card via internal AT command and I perform a system reboot (just to ensure everything starts fresh)
>>
>> With system reboot you mean a modem reboot? Or a host system reboot?
>
>
> I have tried both, but the one I usually do is a host system reboot to ensure a system fresh start.
>
>>
>> > After the reboot and after waiting some time (>5-10 minutes) the Modem is not able to register in any network and the signal quality is never updated.
>>
>> As you said, this should have been automatic. There's no state stored
>> in MM that would affect this IF you did a full host system reboot OR a
>> full modem reset. In both those cases, any state associated with the
>> earlier exposed modem would have gone.
>>
>> To me this looks like a problem with the actual SIM card. Have you
>> tried to start with that 2nd SIM card first, and switch to the
>> original one to see what happens?
>
>
> Ok, it's good to know that the Modem Manager does not store any APN/connection-related information between reboots.
> However, whenever I try to do what you mention I find similar issues. What I experiment is that I am only able to connect using  the SIM I have introduced in the first place.
> It does not matter if I make a reboot, that will be the SIM with which I will be able to connect no matter I try to use it in first place or second (like if the modem stored some APN/connection info)
>
> I will make some more tests but it seems it may be a Modem issue.
>

Instead of doing a full host system, you should do a modem reset
instead, because a full host system does not guarantee a modem reset
implicitly, as the modem may be powered separately.
-- 
Aleksander
https://aleksander.es