digital communications - How much binary data is transmitted across a physical wire in one clock cycle?

How much voltage change, what I'm calling binary data, can be transmitted over a wire at one time in one clock cycle? I understand, I think, binary data is what we call it and the wire doesn't really send out a one or a zero. It is conceptual.

I've been reading the question and have a measure of understanding, but not great. I understand there is a frequency at which voltage is transmitted and represented by us visually/logically as binary data. But how much "data" can be transmitted over a wire in one cycle? Is one cycle one voltage transmission (a bit) across a physical wire? Like Morse code but with computers it ends up being really, really fast (Ghz).

Answer

Actually, the answer to your seemingly simple question is more complex than you'd readily believe!
The short answer is that one signal at a time can be passed through a single signal wire, in one cycle. The amount of data that symbol represents depends on the protocol used.

The long answer is that:

• 2-state protocols, like OOK (On-Off Keying), pass only one bit (on or off) per cycle;



• 1-dimensional multi-state protocols, like FSK(Frequency Shift Keying), PSK(Phase Shift Keying), FM(Frequency Modulation), or AM(Amplitude Modulation), can transfer a few bits of data at once;


• Multi-dimensional multi-state protocols, like QAM(Quadrature Amplitude Modulation), can transmit fairly huge amounts of data in a single cycle (I've seen QAM 512 {9 bits per cycle} advertised).