ITGD3101Modern Telecommunications

Lecture-5- Pulse Code Modulation

week 5- q-2/ 2008

Dr. Anwar Mousa

University of PalestineFaculty of Information Technology

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Contents

Sampling theoremQuantization Pulse Code Modulation

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Aperiodic signal representation by Fourier Transform

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Today, we are going to talk about:

The first important step in any DCS:

Transforming the information source to a form compatible with a digital system

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EncodeTransmit

PulsemodulateSample Quantize

Demodulate/Detect

Channel

ReceiveLow-pass

filterDecode

PulsewaveformsBit stream

Format

Format

Digital info.

Textual info.

Analog info.

Textual info.

Analog info.

Digital info.

source

sink

Formatting and transmission of baseband signal

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Format analog signals

To transform an analog waveform into a form that is compatible with a digital communication, the following steps are taken:

1. Sampling

2. Quantization and encoding

3. Baseband transmission

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Sampling theorem

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Sampling theorem

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Aliasing effect

LP filter

Nyquist rate

aliasing

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Sampling theorem

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Sampling theorem

Sampling theorem: A bandlimited signal with no spectral components beyond , can be uniquely determined by values sampled at

uniform intervals of

The sampling rate, is called Nyquist rate.

Sampling process

Analog signal

Pulse amplitudemodulated (PAM) signal

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Sampling theorem

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Sampling theorem

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Pulse Code Modulation (PCM).

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Pulse Code Modulation (PCM).

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Pulse Code Modulation (PCM).

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Quantization example

t

Ts: sampling time

x(nTs): sampled valuesxq(nTs): quantized values

boundaries

Quant. levels

111 3.1867

110 2.2762

101 1.3657

100 0.4552

011 -0.4552

010 -1.3657

001 -2.2762

000 -3.1867

PCMcodeword 110 110 111 110 100 010 011 100 100 011 PCM sequence

amplitudex(t)

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Pulse Code Modulation (PCM).

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Pulse Code Modulation (PCM).

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Pulse Code Modulation (PCM).

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Advantages of Digital Communications

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Advantages of Digital Communications

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Advantages of Digital Communications

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Summary

We have studies the following topics:Sampling theoremQuantization Pulse Code Modulation

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Contents

Principles of Digital Data TransmissionLine coding ON-OFF Polar BIPOLAR HDB-3

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Today, we are going to talk about:

Principles of Digital Data Transmission

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Principles of Digital Data Transmission

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Line Coder

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Line Coder

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Line Coder

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Line Coding

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Line Coding