Pulse modulation schemes aim at transferring a narrowband analog signal over an analog lowpass channel as a two-level quantized signal, by modulating a pulse train. Some pulse modulation schemes also allow the narrowband analog signal to be transferred as a digital signal (i.e. as a quantized discrete-time signal) with a fixed bit rate, which can be transferred over an underlying digital transmission system, for example some line code. They are not modulation schemes in the conventional sense since they are not channel coding schemes, but should be considered as source coding schemes, and in some cases analog-to-digital conversion techniques.
- Pulse-code modulation (PCM) (Analog-over-digital)
- Pulse-width modulation (PWM) (Analog-over-analog)
- Pulse-amplitude modulation (PAM) (Analog-over-analog)
- Pulse-position modulation (PPM) (Analog-over-analog)
- Pulse-density modulation (PDM) (Analog-over-analog)
- Sigma-delta modulation (∑Δ) (Analog-over-digital)
- Adaptive-delta modulation (ADM)(Analog-over-digital)
Direct-sequence spread spectrum (DSSS) is based on pulse-amplitude modulation.
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