Hello,
We are currently performing power consumption measurements on the Nordic nRF9151 using the PPK2 in LTE-M with an Objenious SIM card.
During our tests, we observed two different network behaviors leading to significantly different current consumption profiles, even when running exactly the same test scenario.
1. Different network attach behaviors and current consumption
The attached screenshots correspond to:
- Same firmware
- Same LTE-M configuration
- Same SIM card
- Same location and radio conditions
- Same test procedure
The test simply consists of:
- Setting
CFUN=1 - Waiting for network registration
- Repeating the same attach sequence again a few seconds later without changing any parameter
Despite this, we observe two different attach behaviors with very different energy consumption, in some cases almost double.
Logs:
[2026-05-26 09:56:37.039] at+cfun=1
[2026-05-26 09:56:37.897]
[2026-05-26 09:56:37.898] OK
[2026-05-26 09:56:38.982]
[2026-05-26 09:56:38.982] +CEREG: 2,"E485","093F9E11",7
[2026-05-26 09:56:40.786]
[2026-05-26 09:56:40.786] +CEREG: 1,"E485","093F9E11",7,,,"11100000","11100000"
[2026-05-26 09:56:47.918] at+cfun=0
[2026-05-26 09:56:49.870] +CEREG: 1,"E485","093F9E10",7,,,"11100000","11100000"
[2026-05-26 09:56:54.306]
[2026-05-26 09:56:54.788]
[2026-05-26 09:56:54.788] OK
[2026-05-26 09:56:54.788]
[2026-05-26 09:56:54.788] +CEREG: 0
[2026-05-26 09:56:57.621] at+cereg=5
[2026-05-26 09:56:58.961]
[2026-05-26 09:56:58.962] OK
[2026-05-26 09:57:02.461] at+cfun=1
[2026-05-26 09:57:03.198]
[2026-05-26 09:57:03.198] OK
[2026-05-26 09:57:04.593]
[2026-05-26 09:57:04.593] +CEREG: 2,"E485","093F9E10",7
[2026-05-26 09:57:05.015]
[2026-05-26 09:57:05.015] +CEREG: 1,"E485","093F9E10",7,,,"11100000","11100000"
[2026-05-26 09:57:15.791] at+cfun=0
[2026-05-26 09:57:22.234]
[2026-05-26 09:57:22.234] OK
[2026-05-26 09:57:22.236]
[2026-05-26 09:57:22.236] +CEREG: 0
[2026-05-26 09:57:26.291] at+cereg=5
[2026-05-26 09:57:27.091]
[2026-05-26 09:57:27.091] OK
[2026-05-26 09:57:29.946] at+cfun=1
[2026-05-26 09:57:30.901]
[2026-05-26 09:57:30.901] OK
[2026-05-26 09:57:32.098]
[2026-05-26 09:57:32.098] +CEREG: 2,"E485","093F9E10",7
[2026-05-26 09:57:32.508]
[2026-05-26 09:57:32.508] +CEREG: 1,"E485","093F9E10",7,,,"11100000","11100000"
[2026-05-26 09:57:41.527] at+cops?*
[2026-05-26 09:57:46.284]
[2026-05-26 09:57:46.284] +COPS: 0,2,"20820",7
[2026-05-26 09:57:46.286]
[2026-05-26 09:57:46.288] OK
[2026-05-26 09:58:36.929] AT%XSYSTEMMODE?
[2026-05-26 09:58:38.099]
[2026-05-26 09:58:38.099] %XSYSTEMMODE: 1,0,0,0
[2026-05-26 09:58:38.105]
[2026-05-26 09:58:38.105] OK
We also observe similar behavior differences during:
- UDP transmissions
- DTLS handshake procedures
However, with other operators (for example Orange), we do not observe these differences, which makes us think this could be related to operator-side LTE-M configuration or network behavior.
Could you please help us understand:
- What LTE-M signaling or network procedures could explain these differences?
2. RAI behavior and inactivity timer reduction in NB-IoT protocol
We are also testing RAI behavior on the nRF9151 in order to reduce the inactivity time after UDP transmissions.
We enabled RAI using:
AT%RAI=2Relevant logs:
AT%RAI=2
OK
AT+CFUN=1
OK
+CEREG: 2,"C3D1","093F9ED8",9
%RAI: "093F9ED8","20820",0,1
+CEREG: 1,"C3D1","093F9ED8",9,,,"11100000","11100000"From the %RAI notification, it seems that:
- AS-RAI is disabled by the network
- CP-RAI is enabled
Based on our understanding, CP-RAI should reduce the inactivity time after uplink UDP transmissions in NB-IoT protocol.
We verified this behavior with another modem platform, where enabling CP-RAI effectively reduces the inactivity duration.
However, on the nRF9151, enabling:
AT%RAI=2does not seem to change the inactivity duration or current consumption behavior after UDP transmissions.
Could you please confirm:
- Is
AT%RAI=2the correct command to enable CP-RAI on nRF9151 for UDP traffic? - Is there a modem trace or debug method allowing us to verify whether the RAI indication is actually transmitted and accepted by the network?
Thank you.