nRF9160 large difference in connection duration

[Willem21]

Dir Sir/Madam,

I let the UDP example run for 20 minutes.
I changed the example to make a second connection after 90 seconds and then every 5 minutes.
Every time it connects it sends 38 bytes of data.
Why is the acivity duration / power consumption so different each time the device connects?
Is the RRC inactivity timer not constant?
Does it depent on the SIM/network provider?

Fullscreen serial log.txt Download

[2023-03-03 17:18:23.667] I: Trace thread ready
[2023-03-03 17:18:23.677] I: Trace level override: 2
[2023-03-03 17:18:23.678] *** Booting Zephyr OS build v3.2.99-ncs1 ***
[2023-03-03 17:18:23.682] UDP sample has started
[2023-03-03 17:18:32.906] LTE cell changed: Cell ID: 1175162, Tracking area: 563
[2023-03-03 17:18:32.948] RRC mode: Connected
[2023-03-03 17:18:35.824] Network registration status: Connected - roaming
[2023-03-03 17:18:35.828] 
[2023-03-03 17:18:35.829] PSM parameter update: TAU: 3600, Active time: 0
[2023-03-03 17:18:35.834] Transmitting UDP/IP payload of 38 bytes to the IP address 8.8.8.8, port number 2469
[2023-03-03 17:19:26.304] RRC mode: Idle
[2023-03-03 17:19:26.306] 
[2023-03-03 17:20:05.841] Transmitting UDP/IP payload of 38 bytes to the IP address 8.8.8.8, port number 2469
[2023-03-03 17:20:06.418] RRC mode: Connected
[2023-03-03 17:22:05.753] RRC mode: Idle
[2023-03-03 17:22:05.755] 
[2023-03-03 17:25:05.848] Transmitting UDP/IP payload of 38 bytes to the IP address 8.8.8.8, port number 2469
[2023-03-03 17:25:06.420] RRC mode: Connected
[2023-03-03 17:25:51.800] RRC mode: Idle
[2023-03-03 17:25:51.803] 
[2023-03-03 17:30:05.857] Transmitting UDP/IP payload of 38 bytes to the IP address 8.8.8.8, port number 2469
[2023-03-03 17:30:06.429] RRC mode: Connected
[2023-03-03 17:31:57.018] RRC mode: Idle
[2023-03-03 17:31:57.019] 
[2023-03-03 17:35:05.866] Transmitting UDP/IP payload of 38 bytes to the IP address 8.8.8.8, port number 2469
[2023-03-03 17:35:06.438] RRC mode: Connected
[2023-03-03 17:38:55.939] RRC mode: Idle
[2023-03-03 17:38:55.940] 

trace-2023-03-03T16-18-16.890Z.bin

trace-2023-03-03T16-18-16.890Z.pcapng

modified udp example.zip

Development setup:
nRF9160DK PCA10090 1.1.0
Power profiler II pca61100 1.0.1
Modem firmware: mfw_nrf9160_1.3.4.zip
NRF Connect SDK V2.2.0
Telenor SIM card (roaming)
Windows 11

With best regards,

Willem

[Willem21]

Hi Simon,

I've no more logging than shown in "serial log.txt", .pcapng and .bin.
How can I enable the logging of "RRC connection"?

Thanks for you reply in advance.

Best regards,

Willem

[Achim Kraus]

You'll see in the pcapng the RRCConnectionRelease. It's always about 20s after the last traffic.

The unintended TCP traffic is then from 15-200s. If you can get rid of it, you have the most done.

If you then want to optimize the left 20s, the consider to use RAI, if that's possible for your use-case.

But the very first thing is to ask your provider.

[Achim Kraus]

> The Wireshark capture still shows TCP IP messages, so think it are the real messages?

Yep, then ask your network provider.

> I use LTE-M to use minimal power.

In my experience, LTE-M PSM without RAI is not better than NB-IoT PSM with RAI (100mC vs. 80mC with about 10s RRC activity timer).

> Is it correct that I can't use RAI with LTE-M?

AFAIK that depends on your provider and the modem support. I've seen someone wrote to use AS RAI for LTE-M (see nRF9160 - AT RAI ), but I never managed to used it successful for now.

[Willem21]

Hi Achim,

We will swap to another provider since the Telenor SIM always uses roaming
and there is no guarantee that PSM/cDRX/eDRX is available.
This case can be closed.

Thanks for the support.

With best regards,

Willem

[Achim Kraus]

> We will swap to another provider 

Just take care. If it's a "global SIM" 9xxxx and you use mfw 1.3.2 or newer, there is a pitfall with HPPLMN searchs (that depends also on the HPPLMN search interval on the SIM). With such a SIM you will be faced a couple of searches for a 9xxxx network, even if your just in a common country. In my case that caused 1800mC every 2h (2h is the search interval on my previous SIM cards).

Good luck. It's not easy to find SIM cards, which are really fits low power use-cases.