RUT955 unstable connection


We are using a Teltonika RUT955 with an O2 Sim at one of our sites in London.

We currently have the main antenna connected, but not the AUX.

Our SSI is usually around -55 dBm but is usually showing as Excellent or, at least good. However, the other signal quality indicators (RSRP, RSRQ and SINR) range from good to fair to poor. In particular, the SINR value regularly fluctuates from between from -15 to 0 within a matter of seconds. As a result, we have a very unstable connection with it regularly going “offline” and often are not able to access the device remotely.

We have tried different network providers and have moved the antenna closer to the window of the building. This resulted in the improved RSSI to “Excellent” but still having issues with the stability.

We are running on the latest Teltonika Firmware and the device has no additional settings changed (it was factory reset before sending to the location). We do, however, have a message on the router saying the Modem Firmware can be updated, but have not been able to do this. Would this help / is it recommended?

I have been reading around the forums and online and have seen suggestions about fixing to specific bands and using a unidirectional antenna. The router will remain in one location and the antenna can remain fixed so this is definitely a possibility, however I am not an expert on Networking and wondered what people would suggest / how to go about this?

Would adding the AUX antenna make a big difference?

Any suggestions / help would be greatly appreciated! I can add / send logs, etc. as requested.


RSSI is only a small part in determining the actual signal quality, and SINR is also very impotant. It is entirely possible to have great RSSI, but very poor SINR (Signal-to-Interference-plus-Noise Ratio) or RSRP (Reference Signal Received Power). Secondary or AUX antenna should improve this considerably, as considering the location, it’s likely that multiple cell towers nearby create interference, which causes the signal quality to drop for all clients. So before trying any other more drastic measures (external antenna, etc.) I’d suggest adding the AUX antenna and see if the signal quality improves.
When SINR value is less than 0, it means that background noise is greater than the signal, thus when SINR value is at -1 or -2, packet loss will increase drastically, resulting in a lot of retransmissions and other faults.
Let me know if adding AUX antenna helps.

Best regards,

Thanks for the response.

We have added the AUX antenna and we are still not seeing much improvement, if any.

The device comes online on the RMS but i struggle to access it and it often times out / disconnects still.


Could you attach a screenshot of the Status → Network → Mobile page? Make sure to remove IMSI, ICCID and Cell ID values for privacy.
You could also try locking the device to a few different bands to see if that improves the connection quality. Instructions on how to configure band locking can be found here: Band Lock - Teltonika Networks Wiki
According to Wikipedia, O2 UK uses these bands for LTE:

So you could try whitelisting only these bands to check if the connection improves:

  • B1

  • B3

  • B20

  • B40

Let me know how it goes.

Best regards,

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