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8 Introduction Chap. 1
If needed, an errata list for this book will also be posted on this website.
The book is also useful as a reference source for mathematics (Appendix A), statistics
(Appendix B and Chapter 6), and MATLAB (Appendix C), and as a reference listing communication
systems standards that have been adopted (Chapters 3, 4, 5, and 8).
Communications is an exciting area in which to work. The reader is urged to browse
through Chapter 8, looking at case-study topics that are of special interest in both wireless and
wire communication systems. To learn more about applied communication systems and
examples of circuits that you can build, see or buy a recent edition of the ARRL Handbook
[e.g., ARRL, 2010].
1–5 USE OF A PERSONAL COMPUTER AND MATLAB
This textbook is designed so that a PC may be used as a tool to plot waveforms; compute
spectra (using the fast Fourier transform); evaluate integrals; and, in general, help the reader
to understand, analyze, and design communication systems. MATLAB was chosen as the
program language since it is very efficient at these tasks and a student version is available at a
reasonable cost. For a brief summary of MATLAB programming concepts and instructions on
running MATLAB, see Appendix C (“using MATLAB”). MATLAB files are provided for
solving the Example problems, the Study-Aid problems, and selected end-of-the-chapter
Homework problems. All of these files run on version 7.11 R2010b of MATLAB. These files
are available for free downloading from the website indicated previously. See Appendix C for
more details.
(Additional MATLAB files for all homework problems marked with the PC ( )
symbol are made available to the instructor and are included with the Instructor Solutions
Manual.)
1–6 BLOCK DIAGRAM OF A COMMUNICATION SYSTEM
Communication systems may be described by the block diagram shown in Fig. 1–1. Regardless
of the particular application, all communications systems involve three main subsystems: the
transmitter, the channel, and the receiver. Throughout this book, we use the symbols as
indicated in this diagram so that the reader will not be confused about where the signals are
located in the overall system. The message from the source is represented by the information
input waveform m(t). The message delivered by the receiver is denoted by m ' (t). The [ ' ]
TRANSMITTER
Noise
n(t)
RECEIVER
Information
input
m(t)
Signal
processing
Carrier
circuits
s(t)
Transmission
medium
(channel)
r(t)
Carrier
circuits
Signal
processing
m(t)
~
To information
sink (user)
Figure 1–1
Communication system.