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nRF9160 eDRX weird behavior + how to properly monitor?

nicolae.georgescu

Hello,

My setup is UDP sample and PPK2 for power measurements. I am trying to figure out the best settings that are available with eDRX set to <= 20.48s, and preferably 5.12 or 10.24. I prefer using LTE-M when available over NB-IoT. PSM is off.

When testing with default UDP sample settings (PSM enabled) i get a very similar power profile to the tutorial (https://www.youtube.com/watch?v=r_dr3Qd8inE). Only difference is in cDRX inactivity timer, i get ~100 ms compared to 300 in the tutorial. All good and normal.

When testing with eDRX i get the following:

  1. the network seems to accept it, meaning i get the callback lte_handler case LTE_LC_EVT_EDRX_UPDATE with the values i set. In one test i set 1110 on LTE-M which is N/A and got back 2621.44 which is the closest value
  2. the power profiler shows an average of 500-600 micro amps with spikes every ~1.2 seconds no matter what eDRX value i set, and even if eDRX is set to "OFF".Also a bit weird since normally with eDRX off i should expect an average current in RRC Idle of ~1 mA (according to Online Power Profiler) and i get about half that.

From the above, to me it looks like i'm getting some pseudo eDRX.

Slight smile

Questions:

1. Do i have eDRX or not? Slight smile

2. If i don't, which is the more likely option, how can i detect this from the code? I would attempt to try NB-IoT in case eDRX does not work on LTE-M.

Attached:

1. Modem trace collector /cfs-file/__key/communityserver-discussions-components-files/4/modem_5F00_trace_2D00_2022_2D00_02_2D00_01T20_2D00_53_2D00_47.991Z.bin 

2. eDRX on with 10.24 s

3. eDRX off

  • +1 in reply to nicolae.georgescu

    Hi Nicolae,

     

    nicolae.georgescu said:
    Is there any approx ETA for the planned improvement on eDRX handling?

    Unfortunately, I do not have detailed timeline, but we are aware of this issue and will address it in the future.

     

    nicolae.georgescu said:
    The local Orange provider in Romania claims they do suport eDRX. It's just that the modem doesn't really enter eDRX. But since it does enter eDRX sometimes from Denmark on different operator perhaps something in the network is not properly set. I just don't know what.

    You should use the XMODEMSLEEP to ensure that you're in eDRX. It will give you the type as a unsolicited notification, so if it returns with type = 2 (eDRX), then you've successfully entered eDRX.

     

    nicolae.georgescu said:
    About (2) above, on the retries. Just to clarify, i am asking in case i do set eDRX but i don't get the callback LTE_LC_EVT_EDRX_UPDATE. Which from tests in Denmark (Copenhagen) it can happen, even from a cell that i previously did get the callback and the device did enter eDRX as measured by PPK2.
    So in the cases i don't get the callback, i will re-try to set eDRX again and hopefully not get rejected by the network. I hope this is ok.

    You could try entering PSM instead in cases where eDRX is not available, but if your application is RX driven (ie. receiving data from a server), I understand that latency can be an issue.

     

    Kind regards,

    Håkon

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