Long registration times after deregistration (MVNO SIM)

RE: Long registration times after deregistration (MVNO SIM)

Øyvind — Thu, 31 Aug 2023 12:15:03 GMT

Sorry for the late reply. The response from our modem team went under my radar.

There has been a similar issue in Europe which turned out to be a bug in the network. Difficult to tell if this is the same in VzW network, we cannot verify the same situation. As a work-around our modem team writes:

"...assuming that this is the same problem, client could remove GUTI to see if the Attach succeeds without GUTI. It can be removed with:

AT+CRSM=176,28643,0,0,0

The command works only if the SIM card contains EPSLOCI file and allows using it. Typically it does."

Please test and provide feedback. Thanks!

Kind regards,
Øyvind

RE: Long registration times after deregistration (MVNO SIM)

Øyvind — Wed, 02 Aug 2023 09:54:58 GMT

Still waiting for more feedback from modem team. Will update as soon as I have more information.

RE: Long registration times after deregistration (MVNO SIM)

Chris Burns — Tue, 01 Aug 2023 16:53:11 GMT

Why do the attach attempts fail? Is there any information in the trace that can indicate why it won't attach?

RE: Long registration times after deregistration (MVNO SIM)

Øyvind — Tue, 01 Aug 2023 12:46:11 GMT

Hello, our modem team have had a look at the logs and provide the following answer:

Yes, there are two backoffs in modem firmware for ATTACH attempts - T3411 (short) and T3402 (long) timers - those are used if ATTACH attempts fails in cells. T3411 used with 10 seconds timeout and T3402 used with 12 min timeout as a default or the one given by NW (available after successful ATTACH or TAU).

In this particular case there seems to be regularly five failing attempts with T3411 periods if none succeeds and then finally wait period with timeout of T3402 after fifth failed attempt. In some test step executions 6th ATTACH attempt succeeds after the long wait period.

Kind regards,
Øyvind

RE: Long registration times after deregistration (MVNO SIM)

Chris Burns — Thu, 27 Jul 2023 16:31:18 GMT

What kind of information do you need about the SIM? It's an eSIM from a MVNO with a profile which treats Verizon as home network and treats AT&T and T-Mobile as roaming networks and can register on all three in Cat-M mode.

I have a bit more information as well. If I simply turn on the radio with AT+CFUN=21 (without specifying a carrier with AT+COPS) and it had most recently attached to AT&T the registration time is very short. And then after several hours of registering and deregistering it will eventually switch to Verizon. So the long delay appears to be related to forcing a switch between carriers. This behavior also holds if I send the AT+COPS command before turning on the modem, so the order of the COPS and the CFUN doesn't appear to affect this behavior.

RE: Long registration times after deregistration (MVNO SIM)

Øyvind — Thu, 27 Jul 2023 08:06:16 GMT

Can you please provide some information on the SIM card that you are using? I will need to forward this to our modem team to look at the trace.

-Øyvind

RE: Long registration times after deregistration (MVNO SIM)

Øyvind — Thu, 27 Jul 2023 07:00:47 GMT

Hello,

Sorry for the delayed answer. During the summer season, our workforce is currently operating with reduced staff levels throughout the company, which may lead to slight delays in our response time as we await additional resources. Rest assured, we are actively addressing all issues and working diligently to resolve them promptly.

I will have a look at the modem trace and get back to you within today or tomorrow.

Kind regards,
Øyvind