As I understand it, I/Q data is the complex representation of any waveform. It enables us to understand two things at any arbitrary point in time:
- The projected amplitude of the waveform.
- The direction of the waveform.
However, it's still unclear to me what makes I/Q data so special.
Logically, I can discern the direction of a waveform implicitly: If I'm talking (or transmitting), I know a signal is travelling away from me. On the other hand, if I'm listening, I know any signal I hear must have been travelling toward me.
And if I want to know the amplitude of a waveform, I can just wait until I see a peak.
This in mind, what sorts of modulations/demodulations would be impossible with real data instead of I/Q data? Respectfully, I'd appreciate an example based on reality as I understand that I/Q data makes the result of a FFT transform deterministic, but I don't really understand why that's relevant.