lopy4 not getting consistent Connection

  • Hi All,

    I am working on a lopy4 with Pysense and sending some values to ttn network every 10sec.
    Github: https://github.com/pycom/workshops/blob/master/pysense-example/main.py

    I have my gateway right next to the lopy4 still i see a lot of missing packets.

    Screen Shot 2019-04-17 at 7.14.46 PM.png

    Please advice!!

  • Hi all,

    Finally i was able to get this around by removing the channel from 8-72 as shown below

    for i in range(8, 72):
    start = 903900000
    f_inc = 200000
    curr  = start
    for i in range(8):
        lora.add_channel(index=i, frequency=curr, dr_min=0, dr_max=4)
        curr += f_inc

  • @jcaron please find the log attachment below, It dint allow me to paste it here..



  • @premkumar2306 Can you provide the frequency/channel for several packets (a good dozen would be great)?

    I'm pretty sure it's a channel mismatch issue. US915 has many many channels (72 IIRC), you need to remove most channels and only keep the ones the gateway actually listens to. There are quite a few posts on the topic in the forum, you should be able to find relevant code.

  • Many thanks!! @jcaron @Eric73 @robert-hh

    Hope the below information helps

    Region: us915
    Gateway: RAK831 (8channel)
    Channel: default
    Antenna: https://uk.pi-supply.com/products/rakwireless-glass-fiber-lora-gateway-antenna
    Metadata: { "time": "2019-04-18T15:16:53.834004389Z", "frequency": 905.1, "modulation": "LORA", "data_rate": "SF7BW125", "coding_rate": "4/5", "gateways": [ { "gtw_id": "premkumar-gateway-chicago-01", "gtw_trusted": true, "time": "2019-04-18T15:16:53Z", "channel": 6, "rssi": -114, "snr": -6.75, "rf_chain": 1 } ] }

    @Eric73 i understand 10seconds might be an over kill for the fair access policy, even if i increase my sleep cycle to 45sec i still get the same problem.

    Interesting finding is that i have another device ttn-node which works perfectly fine for 10sec!! no loss of packets.

    Hope we can get to bottom of this. Thanks cheers!!

  • @premkumar2306 Can you share details of:

    • what gateway you are using
    • what country you are in, and the associated region
    • whether you use the appropriate region on your LoPy4
    • the channel configuration you use on your LoPy 4 (default, or specific channels added/received)
    • the channels the packets are received on
    • the RSSI / SNR of the received packets

    The most probable cause is that there is a mismatch between the channels the LoPy4 sends on, and those your gateway listens on.

    A nano-gateway will for instance listen on a single channel at a time, while by default the LoPy 4 will send on several different channels.

  • Hi premkumar2306, in lorawan you cannot send data every 10 secondes for long time and hope it's work, you must deal with a limited time on air when transmiting (lorawan EU868 i guess?).
    When you send your data to the lorawan stack, sometime it's been delayed and sending a new one will replace the preceding one.
    If you adopt a policy of sending one frame every 2 minutes and you must then receive all frame on your gateway.
    Please note that all gateway are not equal in lorawan, some have only 3 channel and then have 3 channel (one channel is 36 seconde time on air , so approx 36 frame with SF9, more in SF7), some other (more epxensive) can have 15 channel and allow your device to send more frame in one hours (in join request gateway send available channel list to your device).

  • @premkumar2306 What kind of gateway are you using?

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