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

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

Jesper Tiberg — Mon, 06 Apr 2020 15:11:30 GMT

Status update

TL;DR: Problem resolved by Telia as of today!

Telia updated their network configuration and asked me to check back on the issue. I was not able to replicate the problem anymore. No packets are dropped as far as I can see (I verified using my test app linked earlier in this thread).

The resolution came after a couple of days down time on their LTE-M network (while NB-IoT still worked), in case you've noticed.

Does anyone with the same problem still have the issue, then please report back here.

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

Johan — Tue, 18 Feb 2020 14:12:29 GMT

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?

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

torgil — Thu, 13 Feb 2020 07:33:33 GMT

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.

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

Johan — Thu, 30 Jan 2020 10:39:59 GMT

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.

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

Johan — Thu, 30 Jan 2020 10:39:11 GMT

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.

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

torgil — Thu, 30 Jan 2020 10:33:11 GMT

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.

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

Johan — Tue, 28 Jan 2020 13:11:59 GMT

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: +46 771 100 235

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

torgil — Tue, 28 Jan 2020 12:52:34 GMT

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?

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

Johan — Thu, 26 Sep 2019 10:58:28 GMT

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.

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

Jesper Tiberg — Thu, 26 Sep 2019 08:44:29 GMT

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.

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

Johan — Thu, 26 Sep 2019 08:22:25 GMT

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.

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

Martin Lesund — Fri, 30 Aug 2019 07:40:28 GMT

Sounds great, thank you.

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

Jesper Tiberg — Thu, 29 Aug 2019 15:29:13 GMT

Hi,

I've contacted Telia and sent them your description.

I'll let you know how it goes!

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

Martin Lesund — Wed, 28 Aug 2019 13:28:23 GMT

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.

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

Martin Lesund — Fri, 23 Aug 2019 11:24:14 GMT

Could you try to take a new trace?
Please follow this guide: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/how-to-get-modem-trace-using-trace-collector-in-nrf-connect on how to Take modem traces.
The other ones you took was unfortunately invalid.

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

Jesper Tiberg — Fri, 23 Aug 2019 10:40:00 GMT

Great!

Tell me if you want any more measurements from me.

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

Martin Lesund — Fri, 23 Aug 2019 09:15:22 GMT

Hi Jesper,

It would be interesting to look at your logs as well, but the ones you have shared are invalid.

Please follow this guide: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/how-to-get-modem-trace-using-trace-collector-in-nrf-connect on how to Take modem traces.

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

Martin Lesund — Fri, 23 Aug 2019 08:58:26 GMT

Hi,
We will have some engineers traveling to the location to do some extensive measurements and Traces as soon as possible, so we can figure out what is actually happening with the network.
Thank you for your patience.

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

Janis — Thu, 22 Aug 2019 17:08:18 GMT

I have practically same situation, but using NB-IOT. First UDP packet is received than nothing for about 10s and so on. The interesting thing is that I have observed this using 3 different vendor modems. Haven't tested with LTE-M for now.

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

Jesper Tiberg — Thu, 22 Aug 2019 12:03:18 GMT

I placed the test application on Github https://github.com/jtiberg/nrf9160-udp-tester

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

Jesper Tiberg — Thu, 22 Aug 2019 10:18:46 GMT

No, they are not delayed when sending every 500 millis.

For the udp tests I saw that at 600ms interval, the issue was present. At 500ms, it was not.

Using MQTT or even plain TCP might change this number a bit - I guess since several IP package is involved, both due to MQTT and TCP layers.

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

Johan — Thu, 22 Aug 2019 10:02:07 GMT

Does the acks show up delayed even when you send every 500ms?

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

Jesper Tiberg — Thu, 22 Aug 2019 10:00:26 GMT

Yes, I was using QOS_1 as well.

The ack comes back after the "down" period of up to 10s.

I would guess the tcp packages are resent by the TCP/IP stack - but this is nothing I can see myself AFAIK. That's why I did verification and testing with udp packages instead.

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

Johan — Thu, 22 Aug 2019 09:55:54 GMT

Sure I can test with 500ms between packets.

Do you also get a MQTT-ack ie data back (I use QOS_1, ie at least one response ACK) ?

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

Jesper Tiberg — Thu, 22 Aug 2019 09:50:13 GMT

Ok, I'm in Gothenburg area.

I found this issue when I was running a program acting as a "remote button" sending the events over MQTT from a Thingy:91 (both DK and Thingy has the issue).

Funny thing is that there was a day or two last week (when I happened to be traveling to Linköping) where I did not see the "lag" so I thought I had accidentally "fixed" the program during the last update.

Not sure if it was just a good day, if I was on another network, or if it was just due to me being on another cell though...

By the way, since you have the same issue:

Could you see if the problem still persists if you send data at least every 500 millis (see my reply above).