In this example, I proposed to represent two bits for each symbol. 1
Each will represent four symbols, so the overall message will have 8 bits. 2
I just remind you that a symbol is just a chirp, but it just doesn't always start at the bottom frequency. 3
Here are the possible combinations to represent two bits 00, 01, 10 and 11. 4
This makes four symbols to represent all of them. 5
So I have to find four different symbols. 6
The symbols will vary in the following way. 7
We'll start from the reference symbol, which is this one. 8
As we saw earlier, it starts from the bottom frequency up to the highest one. 9
Let's say it represents zero zero. 10
And the second symbol will start from a slightly higher frequency. 11
Go to the highest one and it will differ which the maximum frequency more quickly. 12
So it will finish this sweep by starting again from the lowest frequency. 13
We assigned a binary values 01 to this symbol will then start again from an even higher frequency, 14
then finish the sweep and so on. We will assign the last two combinations which are 10 and 11. 15
These two bits for presentation in LoRa doesn't exist because the number of bit assigned in a symbol 16
is directly linked to the spreading factor. 17
in this example, that would mean that we would have used an SF2 to transmission, but we saw that the spreading factor 18
can go from 5 to 12. 19
So this example with two bits is only a theoretical example that allows us to understand this type 20
of modulation. 21
Anyway, you will not find it in a LoRa transceiver. 22
Now let's have a look at a real example.