Yes, that's basically Quadrature Amplitude Modulation (QAM). You divide the "amplitude vs phase" 2D space into a grid of points (typically 4, 8, 16, 32, ...) an

Yes, that's basically Quadrature Amplitude Modulation (QAM). You divide the "amplitude vs phase" 2D space into a grid of points (typically 4, 8, 16, 32, ...) and assign a code to each. That way you can send 2, 3, 4, 5, (...) bits per symbol. Of course, the downside is that you need a higher signal to noise ratio to resolve which point a symbol represents. Edit: fixed bits per symbol