(Carrierless amplitude-phase modulation (CAP)) We have seen how to modulate a baseband QAM waveform up to passband and then demodulate it by shifting down to baseband, followed by filtering and sampling. This exercise explores the interesting concept of eliminating the baseband operations by modulating and demodulating directly at passband. This approach is used in one of the North American standards for asymmetrical digital subscriber loop (ADSL).
(c) Suppose that is now sent over a communication channel. Suppose that the received waveform is filtered by a Hilbert filter before going through the demodulation procedure above. Does the scheme still work?