Page 40 - Fundamentals of Communications Systems

1.6 Chapter One

want a focus more on the upper layers of the communication stack should refer
to [KR04, LGW00, Tan02] as examples of this higher layer perspective.

1.4 Technology’s Impact on This Text
This text has been heavily influenced by the relatively recent trends in the field
of physical layer communications system engineering:
■ Advanced communication theory finding utility in practice
■ Baseband processing power increasing at a rate predicted by Moore’s law

Physical layer communications (with the perhaps partial exception of fiber
optics) is filled with examples of sophisticated communication theory being di-
rectly placed into practice. Examples include wireless digital communications
and high-speed cable communications. A communication engineer should truly
feel lucky to live in a time when theory and practice are linked so closely. It
allows people to work on very complex and sophisticated algorithms and have
the algorithms almost immediately be put into practice. Because of this rea-
son it is not surprising that many of the prominent communication theorists
have also been very successful entrepreneurs (Andrew Viterbi [VO79] and Irwin
Jacobs [WJ65] being two obvious examples). In this text, we will attempt to fea-
ture the underlying theory as this theory is so important in practical systems
from mobile phones to television receivers.
The reason that theory is migrating to practice so quickly is the rapid ad-
vance of baseband processing power. Moore’s law is now almost outstrip-
ping the ability of communication theory to use the available processing. In
fact, a great paradigm shift occurred in the industry (in my humble opinion)
when Qualcomm, in championing the cellular standard IS-95, started the de-
sign philosophy of designing a system that was too complicated for the current
technology with the knowledge that Moore’s law would soon enable the design
to be implemented in a cost-effective fashion. Because of this shift in the design
philosophy, future engineers are going to be exploring ways to better utilize this
ever increasingly cost-efficient processing power. Since the future engineers will
be using baseband processing power to implement their algorithms, this text
is written with a focus on the baseband signal processing. To reflect this focus,
this text starts immediately with the complex envelope representation of car-
rier signals and uses this representation throughout the entire text. This is a
significant deviation from most of the prior teaching texts but directly in line
with the notation used in research and in industry.
This book is constructed to align with the quote by Albert Einstein:
Everything should be made as simple as possible, but not one bit simpler.
Consequently, this text will be void of advanced topics in communication
theory that I did not see as fundamental in an introductory communication
theory book. Examples of material left out of the treatment in this text include,