. Define Pulse Position Modulation (PPM)
The position of the pulses of the carrier pulse train is varied in accordance with the instantaneous value of the modulating signal. Note that pulse position represents the time of rise or fall of the pulse. Figure represents pulse position modulated signal. The dashed lines in this figure shows the original positions of the pulses. Obviously, in PPM, these positions have shifted in time. The shift is more if modulating signal amplitude is high and vice-versa. The information about the baseband signal lies in the leading edge of the pulse.