Electronic – Why doesn’t wireless transmission and reception require a common reference voltage


so I have been struggling with this for a while now. I have tried to search for the answer but haven't succeeded yet. Here is how it goes:

If we take USART as an example for wired communication between two devices, the TX and RX lines are referred to a common signal(GND) so that a "1" transmitted is also received as a "1", which makes complete sense.
But when we go to wireless communication, how does a receiver interpret the incoming data correctly?
I know that electrical signals differ from EM communication. But why and how is a "1" sent is also received as "1" since there is no reference signal.
Any reference to reading resources would be highly appreciated!

Best Answer

Wired systems rely on current or voltage to carry signals. These can use a common reference, like early telegraph systems that literally used the earth as a signal return. That’s not strictly necessary though: wired systems can use different means to detect the presence of signal, like detecting edges or sensing a carrier signal.

Radios use electromagnetic waves to do that. Waves are dynamic changes in the electromagnetic field, and the receiver only need to be able to discriminate between these changes and background noise to recover the information. RF waves require no physical connection between the transmitter and receiver: they propagate through free space with no physical medium required.

It’s much the same as using light to communicate. You can sense the light being ‘on’, ‘off’, or at some intensity if the difference between it and the background light is large enough. It's why you can see stars at night but not during daytime: sunlight reflecting / mixing with air drowns out starlight. (You can always see stars in space however, even if we can't hear you scream.)

Nevertheless, light waves, being electromagnetic energy like RF, travel through free space too.

Light: Particle or Wave? Yes.

Here's a timeline of the evolution of light wave / particle theory, with a side of Maxwell. http://global.canon/en/technology/s_labo/light/001/11.html