Interpreting RSSI & SNR

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  • November 28, 2016 at 11:22 am #15654
    Lawrence Griffiths
    Participant

    Are there in guides/help on Interpreting RSSI & SNR from a Ping.
    Surveying a site I was Getting RSSI -113db & SNR of -5dbm on SF9.

    I was able to send 1 in 3 times.
    So with an RSSI range -140dB and SNR -20dbm
    It looks on paper I’ve got some head room before I fall off the cliff.
    But on-site experience feels like I’m on the edge of the cliff, so to speak and should try SF11/12 etc.

    Any help welcome

    Lawrence

    November 28, 2016 at 11:57 am #15658
    Jason Reiss
    Keymaster

    Using the Link Check will give the demodulation margin above the SNR floor for the packet spreading factor.

    For BW125 the lora demod SNR floors in dBm are
    SF7 => -7.5
    SF8 => -10.0
    SF9 => -12.5
    SF10 => -15.0
    SF11 => -17.5
    SF12 => -20.0

    For BW250 add 3.0, BW500 add 6.0

    November 28, 2016 at 3:57 pm #15663
    Lawrence Griffiths
    Participant

    Jason, thanks as non RF type apologies for dumb questions but pondering how I use this data.

    So for example on BW125 from your post
    1. I’m seeing approx -12.0dBm on SF9 I should consider using SF10?
    2. I’m seeing approx -9.0dBm on SF9 I could consider using SF8?

    I do hope someone is working on the “How to Commission a LoRaWAN” book

    November 29, 2016 at 7:45 am #15675
    Lawrence Griffiths
    Participant

    Ok can the AT cmd guide be updated please to include the meaning of the Link Check result.

    // From LoRaWAN spec!
    A value of 0 means that the frame was received at the demodulation floor (0 dB or no margin) while a value of 20 for example, means that the frame reached the gateway 20 dB above the demodulation floor.

    Thanks

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