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Digital Pulse Modulation

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Advantages of DPM

The advantages offered by digital pulse modulation Performance

Digital pulse modulation permits the use of regenerative repeaters, when placed alongthe transmission path at short enough distances, can practically eliminate the degradingeffects of channel noise and signal distortion.

Ruggedness A digital communication system can be designed to withstand the effects of channel

noise and signal distortion Reliability

Can be made highly reliable by exploiting powerful error-control coding techniques.

Security Can be made highly secure by exploiting powerful encryption algorithms

Efficiency Inherently more efficient than analog communication system in the tradeoff between

transmission bandwidth and signal-to-noise ratio System integration

To integrate digitized analog signals with digital computer data

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PCM (Pulse-Code Modulation)

A message signal is represented by a

sequence of coded pulses, which is

accomplished by representing the signal indiscrete form in both time and amplitude

The basic operation

Transmitter : sampling, quantization, encoding Receiver : regeneration, decoding, reconstruction

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Operation in the Transmitter Sampling

The incoming message signal is sampled with a train ofrectangular pulses

The reduction of the continuously varying message signal to alimited number of discrete values per second

Non uniform Quantization The step size increases as the separation from the origin of

the input-output amplitude characteristic is increased, the

large end-step of the quantizer can take care of possibleexcursions of the voice signal into the large amplitude rangesthat occur relatively infrequently.

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Quantization

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Quantization

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Requantization

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Companding

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DPCM

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DM

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DM-O/P

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Problems in LDM

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ADM

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O/P