Could you help me with the studying of the theory of Lora modulation.
The Semtech LoRa Modem Design Guide says:
The basic premise of spread spectrum is that each bit of information is encoded as multiple chips.
First question. A “chip” is a group of bits? Why multiple chips?
The substitution of one bit for multiple chips of information means that the spreading factor has a direct influence on the duration of the LoRa packet.
I understand that the Spreading Factor is the number of bits encoded into each symbol (chip?).
And a symbol is an instantaneous change in frequency. So in an unique variation of frequency I associated not only one bit, but more (e.g in SF7 -> 7 bits). I imagine this like a process in which we add more information, redundancy, to obtain a better receive sensitivity.
But why if Spreading Factor increase the Time on air increase too?