LoRa/LoRaWAN tutorial 13: Symbol, Spreading Factor and Chip

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This is part 13 of the LoRa/LoRaWAN tutorial.

In this video series different topics will be explained which will help you to understand LoRa/LoRaWAN.
It is recommended to watch each video sequentially as I may refer to certain LoRa/LoRaWAN topics explained earlier.

In this video I will explain explain what symbols, spreading factors and chips are.

The chirps are cyclically-shifted, and it is the frequency jumps that determines how the data is encoded onto the chirps, aka LoRa modulation.

A symbol represents one, or more bits of data, for example:
Symbol = 1011111 (decimal = 95)
In the example above the number of raw bits that can be encoded by the symbol is 7.
This is the same as saying: Spreading Factor (SF) = 7
The symbol has 2^SF values.
If SF=7, the values ranges from 0 - 127.
The symbol value is encoded onto a sweep signal (up-chirp).

The sweep signal is divided into 2^SF steps or chips.
For example the symbol is: 1011111 (decimal value = 95)
The number of raw bits that can be encoded by this symbol is 7 (SF=7)
The sweep signal is divided in 2^SF = 27 = 128 chips.

Another example, lets assume SF=12
Each symbol can carry 12 raw bits of information and there are 2^12 = 4096 unique chip values ranging from 0 to 4095.
The Spreading Factor (SF) defines two values:
The number of raw bits that can be encoded by that symbol: SF
Each symbol can hold 2^SF chips
Please be aware of the difference between a chirp and a chip.
A symbol holds 2^SF chips.
Chirps are simply a ramp from flow to fhigh (up-chirp) or fhigh to flow (down-chirp).

Check out all my other LoRa/LoRaWAN tutorial videos:
   • LoRa/LoRaWAN tutorials  

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The presentation used in this video tutorial can be found at:
https://www.mobilefish.com/developer/...

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