Many Signals in Modern Communication Systems are digital. Also, analog signals are transmitted digitally. Data transmission, digital transmission, or digital communications is the physical transfer of data (a digital bit stream or a digitized analogue signal) over a point-to-point or point-to-multipoint communication channel. Reduced distortion and improvement in signal to noise ratios is the great advantages of digital transmission over analog transmission. PAM, PWM , PPM and PCM etc., are used to transmit a signal digitally. Pulse Amplitude Modulation (PAM) varies the amplitude of pulses based on the analog signal's amplitude while keeping pulse width constant.
Pulse Width Modulation (PWM) alters pulse width according to the signal amplitude, maintaining a constant pulse amplitude. PWM is widely used in power control and digital systems for its efficiency. Pulse Position Modulation (PPM) changes the position of pulses within a fixed interval according to the signal’s amplitude, it encodes information in timing rather than amplitude. Pulse Code Modulation (PCM) involves sampling an analog signal, quantizing these samples, and encoding them into binary form. For example, these pulse modulation techniques are used in optical fibers, wireless channels, computer buses, etc.