(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.

[torgil]

I've seen the same behaviour when testing nRF9160 using Telia IoT SIM cards. Did you ever get any reply/solution to this from Telia?

[Johan]

I have created a technical support case with them on 2019-09-27.

So far, there has been nothing useful or problem solved from them. Really bad service. 2nd line tech is dealing with it, but it's like they are sleeping on it.

I'm placing a call to them now to check what's going on or why not.

Their number is: [phone]

[torgil]

I had a meeting with a solution architect at Telia yesterday. According to them RLC timeout is set to 5 seconds. This issue remains unsolved.

[Johan]

I see.

I got this error description along the way in talks with Nordic. Telia has this info but still no solution.

• There is radio link problems when the first packet is to be sent by the modem which causes delay because modem goes into RRC IDLE and new RRC CONNECTION must be established for application data.
• Connected mode mobility is not configured and RRC connection reestablishment is rejected by network.

I  called telia in växjö yesterday as well to get someone thre to find out what is going on. She has not reported back as she promised yet.

[Johan]

Well we switched to telenor e-sim cards instead and there is no problem at all. Lightning fast connections and transfers compared to buggy telia.

[torgil]

Just to confirm we have done some experiments using another LTE-M modem (SIMCOM SIM7000e) and we experience the exact same behaviour. Seems to me this is clearly a problem with Telia and LTE-M.

[Johan]

I got info from teliacompany in växjö support level 2/3 that they are doing tests finishing at week 12, regarding the settings for NB/M1.

After w12, they will reach out to customers (they said) with support issues and solve individual cases, or recommend settings.

I gave them contact info to one of nordics contacts I've been in connection with regarding LTE so they can contact  them instead of us (a software dev company using a nording 9160). Let's see how this plays out. Will Telia do their part or screw up again?