Digital communication is a much used term with many shades of meaning,
widely varying and strongly dependent on the user s role and requirements.
This book is directed to the communication theory student and to the designer
of the channel, link, terminal, modem, or network used to transmit and receive
digital messages. Within this community, digital communication theory has come
to signify the body of knowledge and techniques which deal with the two-faceted
problem of (1) minimizing the number of bits which must be transmitted over
the communication channel so as to provide a given printed, audio, or visual
record within a predetermined fidelity requirement (called source coding): and
(2) ensuring that bits transmitted over the channel are received correctly despite
the effects of interference of various types and origins (called channel coding).
The foundations of the theory which provides the solution to this twofold problem
were laid by Claude Shannon in one remarkable series of papers in 1948. In the
intervening decades, the evolution and application of this so-called information
theory have had ever-expanding influence on the practical implementation of
digital communication systems, although their widespread application has
required the evolution of electronic-device and system technology to a point
which was hardly conceivable in 1948. This progress was accelerated by the
development of the large-scale integrated-circuit building block and the
economic incentive of communication satellite applications.