Rak811 Payload and distance /lost package

LPWAN Nodes
1

Dear all,
I was using SF12 to maximum the distance is it correct? As i know when use SF12 then we can send ~50 byte data (I was using 433Mhz). But many times it is can’t send successfully in the first time (my payload 44 bytes) and need to retry many times. So my question is how many bytes to send is the best with Lorawan?

2

SF12 is right at the extreme end and may not be suitable due to the duration of the transmission.

What is the device? Is the device moving? How many gateways are around you? What is the RSSI & SNR you are getting when a message does get through? How far away are the gateways that are receiving from the device? Have you tried any other SF?

3

Hi Nick,
My device is sensor, so it is not moving. I only 1 gateway with 3 node so far. Currently, I can archived about 2km when RSSI ~93 dbm. And never see lower than this value when move longer than distance, actual can’t see data sent success. I saw rak2247 had a sensitivity ~147dbm? Any limit this?
If SF12 is not suitable with long message then what is SF best?

thanks,
Tuyen

4

What is the device? Make, model?

Have you tried any other SF?

When you are 2km away, can you see the gateway’s antenna or are there large buildings/ trees in the way?

5

Hi Nick,
What is the device? Make, model? ==> Not clear your mean. My board was using rak811 and rak2247 module
Not tried yet. I’d like to know theory before try to change.
When you are 2km away, can you see the gateway’s antenna or are there large buildings/ trees in the way? ==> Not see but not large building so much

6

OK, so the device / node / mote is the RAK811.

And you are using a RAK2247 concentrator - is this on a Raspberry Pi?

What antenna (aerial) are you using for the device?

And for the gateway?

Please give a link to the antenna OR provide a picture & details.

Are there any other gateways on the TTN map in your area? You do not have to own it for it to receive your devices uplink.

Google will provide many pages of information on how LoRa modulation works and how that changes with the different spreading factors but there is no harm in actually taking a laptop with the device and trying different rates. Theory is theory but reality always wins, so even if theory says SF10 is appropriate, you may find SF9 works fine or that you have to go to SF11.

It would probably be simpler if you set the RAK811 up for OTAA & Automatic Data Rate (ADR) and let it run for 50+ connections and then look at the logs to see what rate it joined at and what rate it settled at. But I would do both and collect as much information as possible.