This document provides information about the course ECE 3242 Digital Communication for Semester I in 2012-2013. It includes details like the lecturer, textbook, coursework breakdown and assessment. The reading material covers an introduction to communication systems and their essential elements like formatting, modulation, demodulation and synchronization. Key aspects of analog and digital communication are compared and mathematical representations and performance metrics are outlined.

1. ECE 3125
Communication Engineering II
ECE 3242
Digital Communication
Semester I, 2012-2013
1
Semester I, 2012-2013
Lecturer
Prof. Dr. Mohammad Umar Siddiqi
Office: E2-3-10.12
umarsiddiqi@iium.edu.my
03-61964458; 012-6549103

2. Text Book
Digital Communications:
Fundamentals and Applications
2nd Edition
2
2nd Edition
Bernard Sklar
Prentice Hall International

3. Course Work: 60%
Quizzes: 15%
Assignments: 15%
Mid Term: 30%
3
Mid Term: 30%
Final Exam: 40%

4. Reading Material
4
Chapter 1 and Appendix A

5. What is Communication?
Communication
is the transfer of informationis the transfer of information
from one place to another
5

6. What is Electrical / Electronic /
Optical Communication?
It is the transfer of
information from one place toinformation from one place to
another through
electrical/electronic/optical
signals
6

7. Basic Digital Communication System Model
Encode
Transmit
Pulse
modulateSample Quantize
Format
Digital info.
Textual
info.
Analog
info.
source
7
Demodulate/
Detect
Channel
Receive
Low-pass
filter
Decode
Pulse
waveformsBit stream
Format
Textual
info.
Analog
info.
Digital info.
sink

8. Digital Communication System Model
8

9. Digital Communication System (DCS)

10. Communication Systems
Why So Complex ?
10

11. Electrical / Electronic / Optical
Communication
* Transfer of information from one place to
another through electrical/electronic/optical signals
11
another through electrical/electronic/optical signals
* Key feature is the transfer of random signals
over transmission channels with random behaviour

12. This (communication process) should be accomplished
* as efficiently as possible
(bandwidth and power)
bits/sec/Hz for Digital Communication
12
bits/sec/Hz for Digital Communication
* with as much fidelity as possible (for analogue com) - SNR
* with as much reliability as possible (for digital com) – BER
* as securely as possible (using cryptographic schemes)
* as economically as possible

13. Analog vs. Digital Communication
• Analog Communication Systems
– Transmit one waveform out of infinite
possibilities
– Rx “guesses” one out of infinite possibilities– Rx “guesses” one out of infinite possibilities
• Digital Communication Systems
– Transmit one waveform out of finite (limited)
possibilities
– Rx “guesses” one out of finite possibilities

14. Why Digital?
• DSP allows us to condition signal more
flexibly than analog circuits (channel
coding, encryption, equalization))
• Robustness against noise and interference

15. Basic Digital Communication System Model
Encode
Transmit
Pulse
modulateSample Quantize
Format
Digital info.
Textual
info.
Analog
info.
source
15
Demodulate/
Detect
Channel
Receive
Low-pass
filter
Decode
Pulse
waveformsBit stream
Format
info.
Textual
info.
Analog
info.
Digital info.
sink

16. DCS – Essential Elements
• Formatting for compatibility
• Modulation for adaptation to the channel
– Base-band– Base-band
– Band-pass
• Demodulation for extracting the information
• Synchronization for aligning the
timing/carrier frequency between XMT and
RCV

17. Formatting
• To provide proper “interface” between the
information source/sink and the DCS
• to maintain compatibility• to maintain compatibility
• Sampling, quantization, source coding
• Producing bit stream

18. Modulation
• Convert the bit stream into waveform
suitable for transmission
• Base-band: signal with spectrum extending
from zero up to finite bandwidth
– E.g. PCM, M-ary PAM, RZ, NRZ
• Pass-band: signal with spectrum extending
from a carrier frequency (>>signal
bandwidth) up to finite bandwidth
– E.g. M-ary PSK, M-QAM, GMSK
• Include pulse shaping (filtering)

19. Demodulation
• The inverse of modulation
• To recover the message from received
waveformwaveform
• Detection is the process of deciding the
digital meaning of the waveform

20. Synchronization
• XMT and RCV are in general separated
(disjointed) by some distance
• Each has local time and frequency reference• Each has local time and frequency reference
• Imperfect match will result in power loss

21. Mathematical Representation
• r(t): received signal
• si(t): transmitted message symbol
• hc(t): channel impulse response
• n(t): additive noise• n(t): additive noise
• M: size of message symbol

22. Performance Metrics
• ACS (Analog)
– Waveform is member of infinite set
– Signal fidelity (resemblance to the transmitted
waveform)
– Signal to Noise Ratio (SNR), Mean Squared– Signal to Noise Ratio (SNR), Mean Squared
Error (MSE) between transmitted waveform and
received one
• DCS (Digital)
– Waveform is member of finite (alphabet) set
– Probability of error