A multi-modulation scheme is provided that combines pulse-width modulation and phase modulation.

A system for communication over time-based channels includes an input buffer configured to store input digital data and a time domain modulator for generating a modulated waveform based upon the input digital data. Phase shifts in the modulated waveform relative to a carrier signal encode the input digital data within the modulated waveform, the phase shifts corresponding to summations of one or more layering signals with the carrier signal. One or more digital-to-analog converters generate an encoded analog waveform from a representation of the encoded waveform.

A method for communication over a time-based channel using layering signals. The method includes receiving input digital data generating a modulated waveform by modifying an instantaneous amplitude of the modulated waveform relative to an instantaneous amplitude of a carrier signal during selected periods of the modulated waveform in accordance with the input digital data. The instantaneous amplitude of the modulated waveform during each of the selected periods is defined by a summation of one or more layering signals and the carrier signal. At least a subset of the periods of the modulated waveform each represent one or more bits of the input digital data.

A method for layered phase-shifting signal modulation includes receiving input digital data and generating a modulated waveform by combining a plurality of phase-shifting signals with a carrier signal. The generating includes applying, to a carrier signal, a first phase-shifting signal so as to establish a first apparent phase difference between the modulated waveform and the phase of the carrier signal, applying a second phase-shifting signal to the carrier signal so as to substantially eliminate the first apparent phase difference, applying a third phase-shifting signal to the carrier signal to establish a second apparent phase difference between the modulated waveform and the phase of the carrier signal and applying a fourth phase-shifting signal to the carrier signal so as to substantially eliminate the second apparent phase difference wherein the first and second apparent phase differences represent bits of the input digital data.

A system for layered phase-shifting signal modulation includes one or more processors and a memory storing instructions. The instructions cause the one or more processors to receive input digital data and generate a modulated waveform by combining a plurality of phase-shifting signals with a carrier signal. The combining includes applying a first phase-shifting signal to the carrier signal so as to establish a first apparent phase difference between the modulated waveform and a phase of the carrier signal, applying a second phase-shifting signal to the carrier signal so as to substantially eliminate the first apparent phase difference, applying a third phase-shifting signal to the carrier signal to establish a second apparent phase difference and applying a fourth phase-shifting signal to the carrier signal so as to substantially eliminate the second apparent phase difference. The first and second phase differences represent bits of the input digital data.