0
1
00:00:00,720 --> 00:00:04,800
In this example, I proposed to represent two bits for each symbol.
1

2
00:00:05,820 --> 00:00:10,710
Each will represent four symbols, so the overall message will have 8 bits.
2

3
00:00:11,760 --> 00:00:17,880
I just remind you that a symbol is just a chirp, but it just doesn't always start at the bottom frequency.
3

4
00:00:19,110 --> 00:00:27,990
Here are the possible combinations to represent two bits 00, 01, 10 and 11.
4

5
00:00:28,710 --> 00:00:31,440
This makes four symbols to represent all of them.
5

6
00:00:32,730 --> 00:00:35,190
So I have to find four different symbols.
6

7
00:00:35,760 --> 00:00:37,710
The symbols will vary in the following way.
7

8
00:00:38,070 --> 00:00:41,040
We'll start from the reference symbol, which is this one.
8

9
00:00:41,910 --> 00:00:46,140
As we saw earlier, it starts from the bottom frequency up to the highest one.
9

10
00:00:46,950 --> 00:00:49,170
Let's say it represents zero zero.
10

11
00:00:50,610 --> 00:00:54,330
And the second symbol will start from a slightly higher frequency.
11

12
00:00:55,020 --> 00:00:59,910
Go to the highest one and it will differ which the maximum frequency more quickly.
12

13
00:01:00,570 --> 00:01:04,050
So it will finish this sweep by starting again from the lowest frequency.
13

14
00:01:04,770 --> 00:01:11,160
We assigned a binary values 01 to this symbol will then start again from an even higher frequency,
14

15
00:01:11,670 --> 00:01:19,260
then finish the sweep and so on. We will assign the last two combinations which are 10 and 11.
15

16
00:01:20,730 --> 00:01:26,340
These two bits for presentation in LoRa doesn't exist because the number of bit assigned in a symbol
16

17
00:01:26,640 --> 00:01:30,720
is directly linked to the spreading factor.
17

18
00:01:30,930 --> 00:01:36,240
in this example, that would mean that we would have used an SF2 to transmission, but we saw that the spreading factor
18

19
00:01:36,240 --> 00:01:38,220
can go from 5 to 12.
19

20
00:01:38,880 --> 00:01:44,730
So this example with two bits is only a theoretical example that allows us to understand this type
20

21
00:01:44,730 --> 00:01:45,540
of modulation.
21

22
00:01:46,050 --> 00:01:48,660
Anyway, you will not find it in a LoRa transceiver.
22

23
00:01:50,120 --> 00:01:52,290
Now let's have a look at a real example.