Unable to receive SMS without forcing network activity on roaming SIM card

[Daniel Martensson]

Hi,

We are developing an application that should receive commands via SMS. The device runs on a fairly large and rechargeable battery so the power consumption is not the most important.

The SMS receive and send works fine but I have noticed that we only receive SMS after forcing some other network activity such as pushing or pulling IP data. I need the device to wake up on SMS reception.

I use the SMS subscriber library in the modem libraries.

In the simplest of use cases I just call sms_init() followed by sms_register_listener() with a callback function. In this setup I don't receive any SMS. If I then combine this with some code that forces IP data such as code from the udp_with_psm sample I receive the SMS after the UDP NTP activity.

I don't have PSM or eDRX enabled. How can I make sure that I receive SMS when roaming and what latency should I expect (without pushing data I have waited for more than one hour without receiving the SMS ...) ?

I am running a nRF9160 (nRF9160-SICA, BAA-E2.1.8, 11SXH) on a custom board, SW is based on SDK v1.3.0 with modem Firmware 1.2.1. We are running with eSIM and it registers as roaming.

I have logged the following AT commands to verify that PSM and eDRX isn't enabled and to get some information from the network:

CEDRXS:
CEDRXRDP: +CEDRXRDP: 0
CPSMS: +CPSMS: 0
XEPCO: %XEPCO: 1
XDATAPRFL: %XDATAPRFL: 2
XMONITOR: %XMONITOR: 5,"","","24202","09D2",7,20,"01FF5820",485,6300,39,34,"","11100000","11100000","01001001"

The same scenario works fine when not roaming (normal SIM card, not eSIM) and SMS is received instantaneously but the device will have to support roaming and receiving SMS.

Please let me know if you need any further information.

    Best regards,
    
    Daniel.

[helsing]

Hi Daniel,

I am working on this and will get back to you.

Best regards,

Håkon

[helsing]

Hi Daniel,

Sorry for the long wait. I have now got feedback from our team. They say there seems to be some short message routing issue in the core network, probably on the home operator, which in this case would be Telia Denmark. Of course it is possible that this would be because of Telia Norway as well but it is suggested to still start with home operator, Telia DK, on this issue.

Her is another comment:

"subscribe to +CEREG and +CNEC unsolicited notifications from the modem and check/log them after boot. If +CEREG tells them that device is in service (home or roam) but they still see some EMM and/or ESM reject cause value with +CNEC -> then it would be easy to check if this would be a subscription issue, e.g. no SMS when roaming, etc.

To me it looks like in this case there would not be any +CNEC coming because SMS actually starts working after IP data."

Best regards,

Håkon

[helsing]

Hi Daniel,

In other words, contacting Telia DK directly about this issue is our recommended place to start.

Best regards,

Håkon

[Daniel Martensson]

Hi,

Thank you for investigating this issue. Personally I feel that the fact that the SMS only works when pushing data seems to point more to the radio stack than to the foreign network. I don't have much data to hand over to Telia DK to ask them to investigate this issue.

Have you successfully tried SMS reception with a roaming SIM card and in that case with which roaming operator was this tested ?

Could it be a solution that I send you a SIM card so that you could try it out on a standard HW with full access to modem logs ? If that is possible please send me a mail indicating to whom I should send the SIM card.

Best regards,

Daniel

[helsing]

Hi Daniel,

I will discuss this with the team.

Best regards,

Håkon