Hello Im new to the LoRa Community,
Im already did a lot of research because Im writing a paper about LoRa.
Im especially interested about the Spreading Factor in combination with Coding Rate and Bandwith.
I prepared 2 examples which I will include in my research so maybe the community can also give me their opinion about this. Both examples uses payload with 64bytes (51bytes+13bytes header).
- example: Can changing the coding rate outperform another spreadfactor?
Using SF7 with normal coding rate of 4/5 will result in an airtime of 118ms. To have a more reliable signal you could change now the spreadfactor to SF8 with coding rate 4/5 which will result in 216ms of airtime. So my idea would be instead of changing the spreading factor you would increase the coding rate to 4/8 which will still have lower airtime with 187ms and the signal could be even more reliable than with spreadfactor SF8.
- example: Same airtime but more range with higher bandwith
Using SF7 and coding rate 4/7 and 125KHz Bandwidth will result in 164ms of airtime.
Using SF10 and coding rate 4/5 and 500KHz Bandwidth will also result of 164ms of airtime.
Using SF10 and coding rate 4/5 and 125KHz Bandwidth will result in 698ms of airtime.
So far as i understand increasing the Bandwidth will reduce the range but does it also increase the power consumption? And if yes, could the power consumption be less than sending with 125KHz because the airtime is a lot shorter?
Sadly i cannot test the second example by myself with the TTN network because in my region the maximum bandwidth is limited to 250KHz and SF7.
So my last question would also be why the bandwidth of LoRaWAN is limited to 125KHz for most spreading factors.
What would be the downside of having all nodes send in 500KHz which would result in lower airtime?