(LTE-M) IP connectivity available only 3 seconds every 11 seconds

[Jesper Tiberg]

Hi,

Problem description

I wrote a program that initializes the modem (LTE-M) and goes on to send one UDP packet every second (is just the counter).

The server receives the first 2 or 3 packages, but then the next 10 or 11 are lost. This cycle repeats indefinately.

Does anyone know what's going on here?

PSM and eDRX is disabled (would this matter for outgoing data traffic?)

Cellular network is Telia @ Sweden.

SIM-card: iBasis or Telia LTE-M - same result

For a TCP connection (MQTT for example), this problem is slightly masked since (I guess) the lost packages during the 11 second downtime are resent during the 3 second uptime period - so looking at message logs it seems pretty fine unless you look at the time of arrival.

[Martin Lesund]

Hi,
From our extensive investigation on the Telia LTE-M network in Sweden with the nRF9160, we have found that the issue is caused by the network side.

The RLC connection release is not happening, and after that, the new connection cannot be created. This leads to long pauses in data transfers. 
We have tested against the same infrastructure that Telia uses and have not seen this in other networks.

I would recommend contacting Telia Sweden to get this solved.

Best regards,

Martin L.

[Jesper Tiberg]

Hi,

I've contacted Telia and sent them your description.

I'll let you know how it goes!

[Martin Lesund]

Sounds great, thank you.

[Johan]

How did it go @Jesper Tiberg?

If I connect, but don't send anything immediately (wait 30secs - simulating deep sleep pausing), I then send a packet and get a 10.5s delay before any ACK is received. This should happen immediately.
After that ACK is received 10.5s later, I can send new packets and get immediate ACK for every packet.

So there is still something bad in the Telia config. I have not enabled any PSM or eDRX yet either.

[Jesper Tiberg]

After a meeting with Telia, they asked for a full description of the problem and a test session with exact logs of received IP packages.  They got those about 10 days ago.

I'm waiting for a status update, but they have come back with some further questions, indicating they are working on the issue.

[Johan]

All right. Nice to hear.

I have opened a ticket as well with what I saw, so hopefully our both efforts will help them clean up the settings.