It is possible to send a zero-length packet?


(Kiwiclan) #1

I realise I could just try and see. But actually, I wanted to make a suggestion as well. If one could send a zero-length piece of data I expect it would bypass the daily byte count which is I understand 1000 bytes a day. I currently for my device just send one byte, but actually I don't need to send any bytes at all because the device identifier is enough to indicate what I'm sending the byte for (PIR movement detection). Save's one byte of air time if it's possible. It could be counted as one byte for the purposes of still enforcing a daily limit.


(Hylke Visser) #2

Sending zero-length payloads is possible, but the messages will still include the LoRaWAN header of (at least) 13 bytes.

Where did you find the "1000 bytes a day" limit? Because that limit is not based on any official documentation.

The only limitation on uplink is the 30 seconds of airtime per day (the fair access policy). See https://www.thethingsnetwork.org/forum/t/limitations-data-rate-packet-size-30-seconds-uplink-and-10-messages-downlink-per-day-fair-access-policy/1300 for more information.


(Kiwiclan) #3

Yes, I would rely on the headers going through. That explanation is more logical, I may drop the one byte now :slight_smile:

1000 bytes per day was mentioned during a talk at a recent internet of things meetup in Eindhoven.

I would expect 30 seconds to be quite a lot. At the minimum speed of 150kb/s I would still expect the number time of everything including headers and error correction to be under 5ms per transmission, would that be correct?

Kim


(Arjan) #4

Nope, that's too low.


(Gonzalo Casas) #5

That's not the minimum speed either, that's well beyond the max you can get. Data rates for LoRaWAN range between 0.3 kbps to 50 kbps.