I’m using a SIM card from Swiss network provider Sunrise (22802). This provider switched off 2G/3G network services a few months ago. With this SIM card, SMS send/receive always fails either with RUT200 and TRB140. Using the same SIM in a phone (Sony Xperia 1 VI), SMS works fine - maybe I should mention that the phone is using RCS then. In the other hand, if a SIM card from Swisscom (22801) - with 3G still available - is used in RUT200 and TRB140, SMS works smoothly.
Could it be that I have encountered a fundamental problem, or is there a way to get the RUT200 or TRB140 to work with SMS in a 4G-only network with current FW and tweaks?
According to your description, and based on previously reported similar cases with SMS sending/receiving, the root cause usually lies on the operator’s side. Some operators block SMS or call services from non-mobile phone devices such as M2M units, routers, or other IoT hardware. We have also seen cases where, after further investigation, the carrier was found to be rejecting SMS messages or blocking SIM cards when used in such devices.
Therefore, the first step I would recommend is to contact your operator and confirm whether SMS services are supported for non-mobile devices and whether there are any restrictions applied to your SIM card.
Nevertheless, if feasible, for further testing, you might try the following:
Enable the VoLTE option under Network → Mobile → Connection.
Test with a different number format (e.g., 00 instead of +) when sending SMS via WebUI, CLI (gsmctl -S -S "<number> <text>"), or using text/PDU mode with AT commands.
First the low hanging fruit: Yes, of course I set to VoLTE and using CLI AT-command interface, etc. I’m a software ingenieur working since 1996 in GSM mobile comunication generaly and short messaging service specificaly.
And yes, I asked the network operator (Sunrise, 22802) if there are any restrictions to send/receive SMS via IoT-Terminal/Router. The answer was: absolutely no restrictions, more over, we are happy about it, because on a 4G/5G Network a short message (“SMS”) is nothing more than a short datagram over TCP/IP bearer.
I put “SMS” in quotation marks since on 4G/5G networks, there is no longer a Short Messaging Service using the SS7 signaling channel.
If SS7 is still used, then only for legacy device interoperability.
The replacement for SS7 is Diameter, an IP-based signaling protocol designed for advanced services.
I think if you want to keep a SMS like service channel in the Teltonika devices you should consider to implement a RCS (Rich Communication Services) client in the firmware.
Thank you for your update and clarifications. At the moment, there are no plans to implement RCS into RutOS software.
It is possible that your SIM card supports SMS over NAS but not over IMS, which could explain why SMS transmission fails when operating on a 4G-only network, since in that mode, messaging typically relies on IMS. However, please note that this is only a hypothesis.
To investigate this issue further, we would need to continue the communication privately, as collecting device logs, configurations, and other sensitive information would be required. If you would like to proceed with a more in-depth investigation, please let me know here, and I will provide a support request form for you to complete.