How does wifi work, mobile signals and other wireless transmission work?
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Way to broad of a question. This would require several “upper division” college level courses to cover correctly.
The basic idea is that radio transmissions use a carrier frequency which is just a sinewave of a specific frequency. Different modulation methods (amplitude, frequency, phase, on-off keying, etc) are applied to this sinewave which modify it slightly depending upon what signal you are trying to transfer over radio.
On the receiver end, the carrier frequency of interest is filtered from all the other radio waves traveling through space. The modulation is reversed recovering the original message. The software then interprets the message and performs whatever actions are required upon its receipt.
There are numerous topics here–how do you modulate/demodulate, how do you make a transmitter of radio waves, how do you filter a specific frequency, how do you discriminate one message from another using the same standard (i.e. wifi or mobile), etc.
Radio signals are waves of electromagnetic energy. Waves all have different attributes that can be measured, like frequency and amplitude. The wave is generated by whatever device is transmitting information, and the receiver measures different attributes of the wave that it sees on its antenna. The frequency and amplitude of the waves can be changed by the transmitter and interpreted by the receiver. By deciding on a frequency or amplitude that represents a zero, and a different frequency or amplitude to represent a one, your transmitter and receiver can share binary information. Once you can do that, you can create patterns for letters or numbers, just like using Morse code. The signals and protocols get more and more complex to establish things like when the devices are allowed to transmit, how much they can transmit, what type of information they’re allowed to receive, etc.
You can think of it like sending a message using a light and morse code. Instead of using light that humans can see, they use radio waves. And instead of the dots and dashes of morse code, they use the 0s and 1s of binary code.
They’re all just specially designed radios, transmitting and recieivng just like walkie talkies, except using digital encoding (ones and zeros processed by computer chips) to send stuff other than voices. The key is that the transmitters can be very low power, as long as the receivers are sensitive enough, and it works because when the receivers can ignore all the signals (even on the same channel/frequency) except for the particular kind (encoding) they’re looking for, they can be extremely sensitive.
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