[ELI5] For wifi why do we use a whole channel of 20MHz instead of a couple frequencies?

Question

So I get why we can’t use ONE single frequency, it’s sine and we can’t transfer data through it, it’s always gonna be constant. But what about using like 10 or 20 frequencies, something like from 2.4GHz to 2.4GHz10Hz (wrong syntax but you get what I mean). and use it to transfer the data.

I’m gonna give an other potentially wrong example, for radio, don’t we use one single frequency? we set our receiver to that frequency and get the transmitted data from the transmitter? or is it different from wifi because radio is simplex and wifi is half-duplex?

This ended up requiring 2 explanations (wifi and radio) but I’m more interested in the wifi use of a whole 20MHz channel instead of a smaller number of frequencies. Thanks.

In: 2

Answer 1

The frequency you’re thinking of is the carrier frequency, which is basically the frequency on top of which you put the data you need to transfer. The more data per time unit you want to transfer, the wider of a channel around this carrier you need. There are different techniques whit varying efficiency of channel usage, but given a certain technique, the data rate dictates the necessary width of your channel. Even radio is not a single frequency; the frequency you set on your radio is the carrier frequency. There’s still a band around that carrier to “contain” the music.