Thank you for the explanation. I do have a few questions about this, because I believe there are a few things which I can seem to figure out:
- I understand that the maximum sized payload from that chart is 242 bytes and is a limit specified by the LoRa Alliance. I found another article online which states the maximum is 243 bytes, so I guess it’s close enough. Why is the payload maximum size limited to this? I would have though it was something like 255 bytes, but I guess this leaves space for the the 13 byte header?
- I see that the maximum payload sizes have changed between v1.0 and v1.0.2rB. Why is this the case?
- Is the reason for the difference between SF12 having 11 or now 51 bytes versus SF7 having 242 bytes due to airtime? As the SF increase, so does the airtime, which means less data can be sent in the same amount of time. Going by this , does it mean that a payload in v1.0.2rB at SF12 with 51 bytes take as long to transmit as a message at SF7 at 222 bytes? From my experience, I didn’t think SF12 was four times as slow as SF7, I thought it was greater. In addition, my justification doesn’t seem to stand considering the significant change from 11 to 51 bytes between the newer parameters
- Why can’t I transmit the maximum payload size at any SF? I thought duty cycle and fair use policy (which the RN2903 doesn’t consider) was based on a 24 hour period, not on individual transmissions.
The biggest problem I have is this however is that even if I update the firmware, I am still restricted to 51 bytes. This is still not the largest payload I should be able to send. With my current testing, which is about 10 metres from the gateway, I am never operating at SF12 and most often at SF7, as shown by the screenshot above. Why am I limited to maximum payloads of SF12 if I’m not transmitting at that rate and why does the RN2903 assume I am if I am not connected at SF12?
I do understand that TTN does not advise the use of large payloads, but it is still acceptable.