With exceptionally clear writing, Lathi takes students step by step through a history of communications systems from ele
875 31 88MB
English Pages 720 [744] Year 1995
Table of contents :
1. Introduction
2. Analysis and Transmission of Signals
Part I. Signal Analysis
Part II. Signal Transmission
3. Digital Communication Systems
4. Modulation
Part I. Amplitude (Linear) Modulation
Part II. Angle (Exponential) Modulation
5. Probability Theory and Random Processes
Part I. Probabiltiy Theory
Part II. Random Processes
6. Behavior of Communication Systems in the Presence of Noise
Part I. Analog Systems
Part II. Digital Systems
7. Optimum Signal Detection
8. An Introduction to Information Theory
9. Error Correcting Codes
Appendix.
Index.
MODERN DIGITAL AND ANALOG COMMUNICATION SYSTEMS !
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Uploaded to library genesis by M.Talaat Electronics and Electrical Communications Engineering Al Azhar University in Cairo
Modern Digital
and
Analog Communication Systems
The Oxford
Series in Electrical Engineering
M. E. Van Valkenburg, Senior Consulting Editor Adel S. Sedra, Series Editor, Electrical Engineering Michael R. Lightner, Series Editor, Computer Engineering
ALLEN AND HOLBERG, CMOS Analog Circuit Design BOBROW, Elementary Linear Circuit Analysis, 2/e BOBROW, Fundamentals of Electrical Engineering, 2/e CAMPBELL, The Science and Engineering of Semiconductor Fabrication CHEN, Linear System Theory and Design CHEN, System and Signal Analysis, 2/e COMER, Digital Logic and State Machine Design, 3/e COMER, Microprocessor Based System Design COOPER AND McGlLLEM, Probabilistic Methods of Signal and System Analysis, 2/e GhaUSI, Electronic Devices and Circuits: Discrete and Integrated HOUTS, Signal Analysis in Linear Systems JONES,
Introduction to Optical Fiber Communication Systems
KENNEDY, Operational Amplifier Circuits: Theory and Application KuO, Digital Control Systems, 3/e
LASTMAN AND SlNHA, Microcomputer-Based Numerical Methods for Science and Engineering LATHI, Modern
Digital
and Analog Communications Systems,
2/e
LEVENTHAL, Microcomputer Experimentation with the IBM PC LEVENTHAL, Microcomputer Experimentation with the Intel SDK-86 LEVENTHAL, Microcomputer Experimentation with the Motorola MC6800 ECB McGlLLEM AND COOPER, Continuous and Discrete Signal and System Analysis, 3/e NAVON, Semiconductor Microdevices and Materials PAPOULIS,
Circuits
and Systems:
RAMSHAW AND Van
A
Modern Approach
HeeSWIJK, Energy Conversion
SadIKU, Elements of Electromagnetics,
SCHWARZ,
2/e
Electromagnetics for Engineers
SCHWARZ AND OLDHAM, Electrical Engineering: An Introduction, 2/e SEDRA AND SMITH, Microelectronic Circuits, 3/e SlNHA, Control Systems STEFANI, SAVANT, AND HOSTETTER, Design of Feedback Control Systems, 3/e
VAN VaLKENBURG, Analog Filter Design VRANESIC AND ZaKY, Microcomputer Structures WARNER AND GrUNG, Semiconductor Device Electronics WASSER AND FLYNN, Introduction to Arithmetic for Digital Systems Designers WOLOVICH,
Robotics: Basic Analysis and Design
YARIV, Optical
Electronics, 4/e
Modern Digital
and
Analog Communication Systems SECOND EDITION
B. P.
LATHI
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
New
York Oxford Oxford University Press 1995
Oxford University Press
New
Oxford Athens
York
Bangkok Bombay Cape Town Dar es Salaam Delhi Florence Hong Kong Istanbul Karachi Kuala Lumpur Madras Madrid Melbourne Auckland
Calcutta
Mexico City Nairobi Paris Tokyo Toronto
Singapore
Taipei
and associated companies
in
Ibadan
Berlin
© 1989, 1983 by B. P. Lathi
Copyright
Published by Oxford University Press, 198 Madison Avenue,
Oxford
Inc.,
New York, New York 10016
a registered trademark of Oxford University Press
is
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of All rights reserved.
Oxford University
Press.
Library of Congress Cataloging-in-Publication Data Lathi, B.
P.
(Bhagwandas Pannalal) digital and analog communication systems/
Modern 2nd
B. P. Lathi-
ed.
cm.
p.
—(Oxford series in
electrical engineering)
Includes bibliographical references and index.
ISBN 0-19-510500-1
(cl
:
acid-free paper)
Telecommunication systems. 3. Statistical communication theory. TK5101.L333 1995 621.382— dc20 1.
2. I.
Digital communications. Title.
II.
Series.
95-37440
CIP
9
8
7 6
5
4
3
Printed in the United States of America
on
acid-free
paper
To Professor R.
A
pioneer
W. Hamming
in
Information Sciences and Systems
whose writings are
full
of insights.
Contents Preface 1
2
xi
INTRODUCTION 1.1
Communication system
1.2
Analog and
1.3
The signal-to-noise communication
digital
Modulation
I:
I
12
14
AND TRANSMISSION OF SIGNALS
Signal Analysis
16
16
Periodic signal representation h\ Fourier scries
29
2.3
Some
2.4
The sampling theorem
43
properties of the Fourier transform
64
Signal Transmission
72
5
Distortionless transmission through a linear system
6
Signal distortion over a channel
The S The 9 The 10 The 7
bandwidth and
Problems
DIGITAL
72
82
the rate of pulse transmission
energ) spectral density
93
power power
103
spectral densit\
spectral densit) ot noise
I
15
117
References
3.1
17
Exponential representation of nonperiodic signals: The 1-ouner transform
II:
rate ol
9
Randomness, redundancy, and coding
2.2
3
4
channel bandwidth and the
ratio, the
1.5
2.
Part
2
messages
1.4
ANALYSIS Part
1
117
COMMUNICATION SYSTEMS
Conversion modulation
o\
132
analog signals to digital form: Pulse code and Delta 1
34
1
viii
COM Ms I
;
2
!
J
1
4
Digital multiplexing
Line coding
156
Ui2
Pulse shaping
178
3.5 Scrambling
194
The regenerative repeater
3.6
196
3.7 Detection error probability 3.8
\1
-an communication
3.9 Digital carrier systems
Appendix
3.1
Equalizer tap setting computations
Problems
MODULATION Part
222
Amplitude
I:
212
214 214
References
4
203
206 209
(Linear)
Modulation
222
222 Baseband and carrier communication modulation: double sideband (DSB) 223 Amplitude 4.3 (AM) 234 Amplitude modulation 243 4.4 Amplitude modulation: single sideband (SSB) 4.5 Effects of frequency and phase errors in synchronous demodulation 253 4.6 260 Amplitude modulation: vestigial sideband (VSB) 266 4.7 Digital carrier systems 268 4.8 Interference and noise in AM systems 274 4.9 The superheterodyne AM receiver 4.10 Television 277 290 4. Frequency-division multiplexing 4.1
4.2
1
Part
1
II:
4. 12
Angle (Exponential) Modulation
The concept of generalized angle and angle modulation
4.13 Bandwidth of angle-modulated waves 4. 14
294
Generation of
FM Waves 317 FM
294
300
312
4.15 Demodulation of
4.16 Interference and noise in angle-modulated systems 4.17 The FM receiver 337 4.18 Transmission media 4.19 Optical communication
Appendix
4.1
340 344
Phase-lock loop analysis
346
350
References
Problems 5
325
351
PROBABILITY THEORY
AND RANDOM PROCESSES
Parti: Probability Theory
367
5.
Introduction to the theory of probability
5.2
Random
377 averages (means)
variables
5.3 Statistical
397
368
367
1
1
CONTENTS
5.4
The
theorm 407
Partl
II: II.
M Random I
\
1 1
406
central-limit
Correlation I
I
l
I
i
I
Processes »J C33C3 I
I
111 411
».
I
i*
41 rom random variable to random m pixx process ...^ ,v...v. ». a The ul power spectral w^ densirj ol random process >K 4>4 Mulunlc random processes Multiple orocesses 434 I
5.7 5
8
5
'>
transmission
ol
random processes through
5.10 Bandpass random processes 5.11
Optimum
rhe Wienei Hopl
filtering
Problems
Part
I:
435
systems
450
filter
BEHAVIOR OF COMMUNICATION SYSTEMS NOISE
linear
441
453 453
References
6
420
.
IN
THE PRESENCE OF
465
Analog Systems
465
Baseband systems 466 Amplitude-modulated systems 468 477 Vngle-modulated systems 6.4 Pulse-modulated systems 494 6
I
6
2
6.5
Part
II:
6 6
Optimum preemphasis-deemphasis systems Digital
Systems
Optimum
510
threshold detection:
6.7 A/-ar\ communication -
Synchronization
The binar) ease
Problems
I
549
OPTIMUM SIGNAL DETECTION
558
7.2
Geometrical representation of signals: The signal space 565 The Gaussian random process
7.3
The optimum
7.1
receiver
7.4 Equivalent signal sets
7.6 Other useful performance criteria
Appendix References
Problems
604 605
Gram-Schmidt orthogonalization
7.1
6 3 1
8.1
Measure of information
v
Source encoding
619
620
625
8.3 Error-tree communication over a nois) channel 8.4
609
o\ a vector set
612
AN INTRODUCTION TO INFORMATION THEORY 2
559
570 597
7.5 Nonwhite (colored) channel noise
8
51
536
550 550
References
7
505
The channel capacity of
a discrete
63
memoriless channel
635
X
(
DMI MS Channel capacity oi a continuous channel Practical communication systems in the light equation 66 References 668 Problems 668 s 5
8
()
643 Shannon's
oi
1
9
ERROR-CORRECTING CODES 9.
I
Introduction
674
9.2 Linear block codes 9.3 Cyclic codes
674
677
684
9.4 Burst-error-detecting and -correcting codes
692
9.5 Interlaced codes for burst- and random-error correction
694 9.7 Comparison of coded and uncoded systems References 705 Problems 705 9.6 Convolutional codes
A 711 A.l Trigonometric identities Appendix
A. 2 Series expansion 711 A. 3 Summations 712 A. 4 Indefinite integrals
Index
715
712
711
702
693
Preface The stud) of communication systems can be divided into two distinct areas 1.
2.
The
How communication How the) perform in
systems work the presence ol noise
two areas, in turn, requires specific tools To Stud) the first area, must he familiar with signal analysis (Fourier techniques), and to study
studs of these
the students
the second area, a basic understanding of probability theorv
is
essential.
For a meaningful comparison of various communication systems, it is necessar) to have some understanding of the second area. For this reason most instructors feel that the study of communication systems is not complete unless both oi the areas are covered reasonably well. As one o\ my colleagues put it. "I cannot imagine teaching communication systems without teaching their behavior in the presence of noise."
Most of
material to be covered
whelming:
The
However, it poses one serious problem: the enormous. The two areas along with their tools are over-
us will agree with this sentiment.
it
is
is
difficult to
cover
this material in
depth
in
current trend in teaching communication systems
one course is
to stud) the tools
m
early
chapters and then proceed with the study of the two areas of communication. Because too
much
time
is
spent
in
the beginning in studying the tools (without
much mo-
two proper areas of communication. Consequently, teaching a course in communication sv stems poses a real dilemma. The second area (statistical aspects) of communication theory is a degree harder than the first area, and it can be properly understood only if the first area is well assimilated. One of the reasons for the problem is our attempt to cover both areas at the same time tivation), there
is
little
time
left
to study the
The students are forced to grapple with the statistical aspects while also trving to become familiar with how communication systems work. This practice is most unsound pedagogically because it violates the basic fact that one must learn to walk before one can run. The ideal solution would be to offer two courses in sequence, the first course dealing w ith how communication systems function and the second course dealing with statistical aspects and noise. But
competing courses,
it
is
difficult to
in the
squeeze
in
many commu-
present curriculum, with so
two basic courses
in
the
nications area.
There it is
is.
however, a way out of this difficulty. A careful examination shows that go into probabilistic aspects (at least in the first course) in
really not necessary to
xi
xii
PRLFACE
order to study comparative behavior
in
the presence of noise.
analog
In
commu-
nication systems, the noise can be treated as an interference, and using a Rayleigh
model
to represent noise as a
sum of
sinusoids,
it
is
possible to find the noise output
from these interfering sinusoids. This model uses the frequency domain description (the power spectral density) of noise and permits the derivation of noise power outputs and signal-to-noise ratios, and the discussion of the relative merits ot various systems without requiring any statistical description of noise. The additional advantage of this approach is that, here, the power of a signal is a time average rather resulting
than an ensemble average.
Time averages are much more direct and easier for the course. The concept of ensemble averages is rather
students to understand in a
first
confusing to a beginner.
appreciation requires a level of maturity that
Its
able to expect from an average undergraduate in the very
systems. Also, in digital communication systems,
if
we
first
course
in
unreason-
is
communication
consider threshold detection,
the error probability depends only on the difference of strengths of pulses to be
distinguished.
The
relative
performance of various schemes (such as on-off, polar,
bipolar, etc.) can be determined with ease. For example, for the (that is, the
same
error probability),
we can show,
same noise immunity
without any recourse to
statistical
concepts, that the on-off or bipolar requires two times the power needed for the polar
scheme. Even the determination of error probability, which amounts
to
determining
some value, requires only a modest Thus to study the comparative behavior
the probability that the noise amplitude will exceed
discussion of the probability density function.
of communication systems (digital and analog)
by and
large, to avoid statistical concepts
in the
presence of noise,
and ensemble averages.
I
it
is
possible,
have found
this
most appropriate way of dealing with the dilemma mentioned earlier. The first four chapters in this book follow precisely this philosophy. These chapters treat in depth how digital and analog communication systems work and how they behave in the presence of noise in the manner discussed above. Thus, they form a sound, well-rounded, comprehensive survey course in communication systems that is within the reach of an average undergraduate and that can be taught in three to four semester hours. Once the students have mastered the first four chapters, they are ready for an in-depth treatment of statistical concepts in communication theory. Chapters 5 through 9 provide such a treatment and are appropriate for advanced undergraduates to be the
or graduate students.
Chapter
1
introduces the students to a panoramic view of communication systems.
All the important concepts of communication theory are explained qualitatively in a heuristic
way. This gets the students deeply interested and they are encouraged
study the subject. Because of this
momentum,
to
they are motivated to study the tool of
signal analysis in Chapter 2. Signal distortion caused by various types of channel
imperfections
is
also discussed in this chapter. Chapter 3 deals with digital
nication systems, including the digital transmission of analog signals
(PCM
commu-
and DM).
Chapter 4 discussed linear and exponential (or angle) modulation of a carrier by analog as well as digital signals. Chapter 5 is a reasonably thorough treatment of the theory of probability and random processes. This
is
the second tool required for the study of
communication systems. Every attempt is made to motivate the students and sustain their interest through this chapter by providing applications to communications prob-
PREFACE
xiii
lems wherever possible. Chapter 6 discusses the behavior of communication systems presence of noise this tunc using ensemble averages Optimum signal de-
—
in the
discussed
Chapter
and information theor\ is introduced in Chapter X. m Chapter 9. Analog pulse modulation systems such as PAM, PPM. and are deem phasized in comparison to digital schemes (PCM and DM) because the applications tection
is
in
Finally, error-control coding
is
7.
discussed
PWM
of the former in communications are hard to find. The digital schemes are used u ulek
now and receives
will be
used even more uidek
in
the future.
share of deemphasis tor a sound reason.
its
KM
Tone-modulated
also
Since angle modulation
is
nonlinear, the conclusions derived from tone modulation cannot be blindly applied to
modulation by other baseband signals
In tact, these
conclusions are misleading
many instances. For example, in the literature PM gets short shrift as to FM, a conclusion based on tone-modulation analysis.* It is shown and 6
PM
that
this reason,
is, in fact,
tone-modulated
the comparison In
my
superior to
o\'
earlier
FM
with
FM
FM
in
Chapters 4
for all practical cases (including audio). For
deemphasized and more space
is
in
being inferior
is
devoted
PM
to
and
PM.
books {Signals, Systems and Communication, Wiley, 1965 and had devoted a great deal of space and effort
Communication Sxstcms, Wiley. 1968). to signal-vector analogy. In
I
terms of the time available, signal-vector analog)
.
despite
which we can now ill afford due to the addition of several new areas to communication. For this reason, in the present book, the signal-vector analogy is omitted and the study of signal space is postponed to Chapter 7. Chapters 2. 4. 5. and 6 each have two parts. Each of these chapters could easily have been split into two separate chapters. I have avoided this temptation for a good reason. When a subject is fragmented into too many chapters, beginning students are confused and bewildered by the proliferation of seemingly endless topics and they fail to see the interrelationship between them. On the other hand, it is easy to see the whole when it is divided into fewer but well-defined parts. The situation is similar to a visit to a big mansion. When a first-time visitor sees many rooms, he is confused and bewildered and fails to see the wholeness of the mansion. But if a guide carefully divides the mansion into fewer but more well-defined areas such as living area, its
charm,
is
a luxury
sleeping area, recreation area, etc.,
and
its
relationship to the
One
of the aims
in
least a less intimidating
whole
much
it is
easier to grasp the purpose of each
writing this book has been to
make
learning a pleasant or at
experience for the student by presenting the subject
understandable, and logically organized manner. Every effort has been
an insight
—
theoretical
rather than just an understanding
wherever possible.
results
clarification of abstract results.
would make
*
all
mv
toils
Another reason given
to a value less than
signals.
it.
It
room
structure.
Even
—
in a clear,
made
to give
as well as heuristic explanations of
Many examples
are
provided for further
a partial success in achieving
my
stated goal
worthwhile.
for the alleged inferiority of
has been
shown
in
Chapter 4
PM
is
that the
that this
is
phase deviation has to be restricted
simply not true of bandlimited analog
PREFACE
xiv
It
a pleasure to
is
acknowledge
during the preparation of this book.
the assistance received
Many
from several individuals
students have helped
me
to prepare illustra-
Dave Lewis, Yu/o Yano (computer generated plots), Ron Taylor and Arnel Guanlao (editing). I am indebted to Professor Warren Smith and Mahlon Heller for contributing some items to the problem sets in this edition. thank Professors Rudolph Engelbrecht and Zhang Su-Wen for pointing out some typographical errors in the first edition. Thanks are also due to three anonymous reviewers for their helpful comments. tions
and
to proofread.
I
would
particularly like to mention
I
Finally,
I
owe
a debt of gratitude to
my
my
family:
Anjali and Pandit for their patience and understanding.
my
wife Rajani,
A
children
mere "thank you"
cannot make up for the hardships they suffered on account of
this
really
book. B. P. Lathi
A Note
to Instructors
This book can be used for a variety of undergraduate and graduate level courses in
communications systems and theory. With a judicious selection of topics, the book can be used for a one or two-semester (or quarters) sequence in the area of communication. Sufficient material is included to allow flexibility in adopting the book for a variety of courses. I.
Some
possible options are suggested below:
Undergraduate courses which do not require probability theory 1. A survey course in communication systems: Chapters 1, 2. 3, and 4
(3 to
4 semester-hours or 4 to 6 quarter-hours). Sections dealing with noise (Sees. 2.10, 3.6, 4.7, and 4. 16) can be omitted,
if
so desired, without loss
of continuity. 2.
Modulation theory and noise calculations: Chapters
2,
1,
and 4
(3
semester-hours or quarter-hours). 3.
Digital communications: Chapters
1,
2,
and
3,
and possibly 9 (2
to 3
semester-hours or 3 to 4 quarter-hours). II.
Advanced undergraduate or Statistical theory
2.
Analog communication of
graduate-level courses
of communication: Chapters 5 and 6 or 5, 6, and
1.
in noise:
Chapters
1, 2,
4 (review),
5,
7.
and Part
I
6.
3.
Digital communications: Chapters
4.
Information theory and coding: Chapters 8 and
1, 2,
3 (review), 5, Part 9.
II
of 6, and 7.
Introduction
This book examines communication b\ electrical signals.
In the past,
messages have
been carried by runners, carrier pigeons, drum beats, and torches. These schemes
were adequate for the distances and "data rates" of the age. In most parts of the world, these modes of communication have been superseded by electrical communication systems* that can transmit signals over
and galaxies) and Electrical
at the
speed of
communication
will alleviate the
energy
crisis
is
much
longer distances (even to distant planets
light.
reliable
and economical: communication technology
by trading information processing for
use of energy resources.
Some examples:
nicated face-to-face
meetings or conferences, often requiring
in
a
more
Important discussions now mostl) travel,
rational
commuwill
in-
creasingly use "teleconferring." Similarly, teleshopping and telebanking will provide services by electronic
news
*
communication, and newspapers
services.
With the exception of the postal service!
will be replaced
by
electronic-
2
l
M-M'IIK
1
IMK( MH
(
HON
COMMUNICATION SYSTEM
1.1
II shows three examples of communication systems. A typical communication system can he modeled as shown in Fig. 1.2. The components ol a commuFigure
nication system arc as follows:
The source a teletype
originates the message, such as a
message, or data.
If
the data
is
human
nonelectrical
voice, a television picture,
(human
voice, teletype mes-
must be converted by an input transducer into an trical waveform referred to as the baseband signal or the message signal. The transmitter modifies the baseband signal for efficient transmission.* sage, television picture),
Figure 1.1
*The
Some examples
it
of
communication systems.
transmitter consists of one or
more of
the following subsystems: a preemphasizer. a sampler, a
quantizer, a coder, and a modulator. Similarly, the receiver filter,
and a deemphasizer.
elec-
may
consist of a demodulator, a decoder, a
C
_.
-
Q.
s
_-
= A r 3 n _
*~v
w
*
o
^
\j
a 2£
— _> **
^
_
w
~
,1
•J
e f
'->
BO
2i
7
:-»
55
E
s -
J5
—y
*-'
-
c od
X.
o B C M -
—
M -
^ k
u.
s
-
— E y c ed k_
—
a
—
'
r,
*
.
'j
-
>
^-
E E c
~
u
r
.
t.
then
if /(f) is
all
the sine terms in
an odd function oi
the cosine terms in the series vanish {aH
-
t.
for all n).
its
Fourier series vanish
then the constant term and
Moreover, the computation
of nonvanishing coefficients requires integration over only half the period. The proof is
relatively simple (see Prob. 2.1-1).
EXAMPLE
2.2
Find the Fourier series for the rectangular pulse train k(t) shown the period
is
=
T. f
T
1
and
.
to
in
Fig. 2. 4a.
Here
= 2w/ = 2- T
x
kit)
a
-
= i
a„
bn
^
+
a
=
—2 Tto
=
kit) dt i
=
+ bn
t
-
J
A
,
cos
nto,.t
at
=
—
(2.11a)
2A
.
sin
nirr
-^-
(2.11b)
T
:
A
\
J
— Trn
]-r/ J-t/2
t
I
:
-
r-
sin nto
Adt =
\
i
:
i
—2 r h
cos nto
a,,
-
sin nto
j
dt
=
:
Hence x
k(t)
= C +
2 n=\
C
"
cos (nu)^
+
dn)
(2,,2a)
22
(HMMIKJ
TRANSMISSION
-\NM>i SIS -\\[)
sin
2 lim 7—0
T
(
\
n-T — /
(f) /177T\
~z)
5
(2.14b)
T The
last result
sin
follows from the use of [/Hospital's rule to obtain
x
lim
* In fact
any odd multiple of tt. ^This also follows from Eq. (2.6). -tan [0/(-2/A/3)] = -tt. '
If
a?
= -2/4/3
and
b,
=
0.
then C?
= 2A/3« and
ft.
=
24
IMMMIKJ \S\ns|s
\\[) |k\\s\Mss|