nRF9160 connectivity & configuration help

RE: nRF9160 connectivity & configuration help

Momchil_MRP01 — Wed, 24 May 2023 19:11:35 GMT

I think we just reached resolution to this issue stated by JonathanF by having our SIM provided changing the IMSI rules affecting profile rotation and connection registartion using specific IMSI to a tower.

The suggestion by Heii-Irene was in fact the issue

You're using a SIM card that has several profiles and is able to switch between those. What could be happening is that some of the location status events are not being forwarded from the modem to the SIM card and thus the SIM card is not able to perform a SIM refresh to change its profile and allow LTE registration.

The SIM provide had rules setup for specific IMSI that caused Service Rejection (from Cell tower provider) rather than Home Rejection (from the SIM card provider). Service Rejection was then not translated to SIM card rotation and at that physcal location the device was only in search and connect to tower state but never registered to the provider or changed IMSIs.

Example message: +CEREG: 4,"FFFE","FFFFFFFF",7,0,15,"11100000","11100000"

Cause #15 – No suitable cells in tracking area

This EMM cause is sent to the UE if it requests service, or if the network initiates a detach request, in a tracking area where the UE, by subscription, is not allowed to operate, but when it should find another allowed tracking area or location area in the same PLMN or an equivalent PLMN.

RE: nRF9160 connectivity & configuration help

Heidi — Mon, 26 Jul 2021 09:17:17 GMT

The communication for this ticket has been moved to email but I am adding a summary here for future reference.

The consensus is that the UE is having issues with poor signal levels. They have looked for other causes of disconnection but determined the low signal level as the strongest indicator.

RE: nRF9160 connectivity & configuration help

JonathanF — Thu, 08 Jul 2021 15:14:29 GMT

Hello,

My apologies for taking so long to circle back on this. We've still been seeing some similar issues w/r/t transitioning from CFUN=4 to CFUN=1. I've created a simple firmware image that does repeated cycles to CFUN=4/CFUN=1 and measures the reconnection time, along with traces.

I've attached a ZIP file with the relevant files.

src/main.c and prj.conf are built against v1.6.0 nrf SDK running w/1.3.0 modem firmware.
2021-07-08--083113---putty.log shows the UART output
trace-2021-07-08T13-18-51.639Z.bin contains the modem trace

An example of the timeout is in the logs "Network connection attempt timed out". What's odd is that the reconnections *mostly* happen quite quickly (within 5 seconds). But sometimes they do time out, despite the network conditions seemingly not changing.devzone.nordicsemi.com/.../network_2D00_timeout.zip

Thank you,

Jonathan

RE: nRF9160 connectivity & configuration help

Heidi — Thu, 03 Jun 2021 13:10:38 GMT

Hi!

We recommend all customers transition to nRF9160 SiP Rev 2, as MFW 1.3.0 and nRF9160 SiP Rev 1 will not be a widely certified combination.

I can make this case private and we can discuss your specific use case (i.e number of chips, reason you can't transition to Rev2) if you would like.

With regard to Verizon certification, contact your RSM, David Day (david.day@nordicsemi.no), for information on this.

Best regards,

Heidi

RE: nRF9160 connectivity & configuration help

JonathanF — Wed, 02 Jun 2021 14:06:40 GMT

Hi Heidi,

Thank you for the response. Given this response, we will prioritize adoption of 1.3.0. Can you give any guidance on using 1.3.0 for Revision 1 hardware (nRF9160 SICA B0A)? The release notes currently specify that 1.3.0 should only be used for development and testing; what sort of limitations are there with Revision 1 hardware?

Similarly, do you expect Verizon certification to happen for 1.3.0? And, if so, what is the timeline on that?

Thank you,
Jonathan

RE: nRF9160 connectivity & configuration help

Heidi — Mon, 31 May 2021 13:05:45 GMT

Hi!

The scenarios described can happen when the device is coming out of airplane mode.

Furthermore, the modem team let me know that unless this issue is present on MFW 1.3.0 where there are fixes to multi-SIM operation, they will not work on this case.

RE: nRF9160 connectivity & configuration help

JonathanF — Wed, 26 May 2021 23:48:49 GMT

Hi Heidi,

Thank you for the reply. How would either of the scenarios that you outlined work when the device is coming out of airplane mode (CFUN=4)?

Here is the initialization sequence we're using:

AT+CPSMS=1,,,"01100000","00000000"
AT+CGDCONT=0,"IP","eseye1"
AT+CEREG=5
AT%CESQ=1
AT+CSCON=3
AT+CNEC=24
AT%XSIM=1
AT+CFUN=1

As you can see, we have the CEREG and CSCON messages enabled. Presumably we do not need to re-set these every time after coming out of Airplane mode.

I was able to reproduce the issue on the devkit earlier today, but not with a trace running. I will attempt to do this overnight tonight.

I understand that v1.3.0 is improved, and we do intend to move to that when possible. As it stands now, we do not currently have support for updating modem firmware OTA; that work is ongoing. We also need to make sure that all of the devices we've currently manufactured are supported by v1.3.0.

Thank you,
Jonathan

RE: nRF9160 connectivity & configuration help

Heidi — Wed, 26 May 2021 13:02:36 GMT

Hi!

So there are few scenarios where this 'not searching' can happen.

SIM init fails.
There is a fatal/permanent reject for LTE registration, e.g. #8 (EPS services and non-EPS services not allowed), or #3 (Illegal UE), etc.

The above cases can happen occasionally, e.g. if the card can move in the reader, or due to some network issue. But these occasions should be quite rare.

If you're able to take a modem trace when the case you described happens we would be able to see this.

Did you activate the unsolicited CEREG notifications before CFUN=1 was sent?

Side note, there are many improvements in multi-profile SIM card functionality and AT+CEREG notifications in MFW v1.3.0, so I strongly advise you to update to the newest MFW release. If at all possible, a modem trace from the old and the new modem FW would be very interesting to see.

Best regards,

Heidi

RE: nRF9160 connectivity & configuration help

JonathanF — Fri, 21 May 2021 12:59:04 GMT

Hi Heidi,

Thank you for the responses! We are currently using modem firmware 1.2.0, and we run with this flow:

Modem is connected to the network.
We put the modem into flight mode: CFUN=4.
<Wait 60-120 seconds>
We put the modem back into search mode: CFUN=1.
We query CFUN, CEREG and CSCON every 10 seconds

More often than not, the modem will connect to the network once we put it back into Normal functional mode. But sometimes this doesn't happen; the device remains in Normal mode, but never connects to the network, and seemingly never tries.

In the case being discussed (CFUN=1, but no connection is ever made), the responses are like this (I've had it run for over a day, and the response is always the same):

CFUN response: +CFUN: 1

CEREG response: +CEREG: 5,0,"040A","00FE4611",7,0,0,"11100000","11100000"

CSCON response: +CSCON: 3,0,7,4

What I notice is that the CEREG query returns status 0 (not searching) after issuing the CFUN=1 command. As such, there are no notifications ever issued, and no connection will ever be made. This doesn't happen every time, but once it does happen, we never get out of this mode.

Do you have any guidance on how to handle this?

Thank you,

Jonathan

RE: nRF9160 connectivity & configuration help

Heidi — Thu, 06 May 2021 11:24:13 GMT

1. Yes, this means the modem has completed the network search, but no available networks were found.

2. There is no way to erase the configurations store in NVM in the current modem FW releases. In the next MFW release there will be a setting to do this.

4. Searching is started immediately, but the modem will send +CEREG information after it has found a suitable cell for service and registration to the network has been performed, or it has searched whatever it is going to search without success. The time varies based on the current radio environment.

RE: nRF9160 connectivity & configuration help

Heidi — Mon, 03 May 2021 13:46:37 GMT

Hi!

1. I have forwarded this question and I'll let you know when I hear back.

2. Yes, I believe it's possible to erase the configurations stored in NVM. I will check how to do this.

3. You should only use AT+CFUN=0 when you want the current modem configurations to be stored. If that isn't necessary, then use AT+CFUN=4 instead. The flash also has a limited amount of reads and writes, so we recommend AT+CFUN=0 only when necessary.

[quote user=""]Our approach has been to transition to airplane mode when we wish to save power, but when an unpredictable reset happens (via a user event), we want to be able to reasonably quickly connect to the network again.[/quote]

It sounds like you are doing it correctly.

4. I'm not sure if 60 seconds is a normal time to wait for signal notifications. I'll consult with the modem team and get back to you.

Best regards,

Heidi