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Unformatted text preview: Chapter 1 Introduction to digital communication Communication has been one of the deepest needs of the human race throughout recorded history. It is essential to forming social unions, to educating the young, and to expressing a myriad of emotions and needs. Good communication is central to a civilized society. The various communication disciplines in engineering have the purpose of providing technological aids to human communication. One could view the smoke signals and drum rolls of primitive societies as being technological aids to communication, but communication technology as we view it today became important with telegraphy, then telephony, then video, then computer communication, and today the amazing mixture of all of these in inexpensive, small portable devices. Initially these technologies were developed as separate networks and were viewed as having little in common. As these networks grew, however, the fact that all parts of a given network had to work together, coupled with the fact that different components were developed at different times using different design methodologies, caused an increased focus on the underlying principles and architectural understanding required for continued system evolution. This need for basic principles was probably best understood at American Telephone and Tele- graph (AT&T) where Bell Laboratories was created as the research and development arm of AT&T. The Math center at Bell Labs became the predominant center for communication re- search in the world, and held that position until quite recently. The central core of the principles of communication technology were developed at that center. Perhaps the greatest contribution from the math center was the creation of Information Theory  by Claude Shannon in 1948. For perhaps the first 25 years of its existence, Information Theory was regarded as a beautiful theory but not as a central guide to the architecture and design of communication systems. After that time, however, both the device technology and the engineering understanding of the theory were suﬃcient to enable system development to follow information theoretic principles. A number of information theoretic ideas and how they affect communication system design will be explained carefully in subsequent chapters. One pair of ideas, however, is central to almost every topic. The first is to view all communication sources, e.g., speech waveforms, image waveforms, and text files, as being representable by binary sequences. The second is to design 1 Cite as: Robert Gallager, course materials for 6.450 Principles of Digital Communications I, Fall 2006. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 2 CHAPTER 1. INTRODUCTION TO DIGITAL COMMUNICATION communication systems that first convert the source output into a binary sequence and then convert that binary sequence into a form suitable for transmission over particular physical media...
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This note was uploaded on 02/21/2012 for the course ECON 830 taught by Professor Staff during the Spring '08 term at Michigan State University.
- Spring '08