Digital Communication: Part I–Fundamental Architecture
This course focuses on digital signaling methods, error-correction coding, multiple-access, spread-spectrum techniques, and bandwidth-efficient signaling in the context of wireless-radio and satellite systems. It starts with a checklist of questions and ideas that represent essential technical concepts behind all digital communication systems. When participants become proficient in these fundamentals and feel comfortable with the issues, they become adept at applying them to any such system—all telecommunication and radio systems share the same electrical relationships. Many applications of successful design examples are reviewed. The sessions strive for intuitive insight and the transfer of advanced technology in an organized way.
This course, abstracted from the original, emphasizes the fundamental architecture of modern communication systems. It covers what every communications engineer should know about digital communications. It also serves as the prerequisite for the follow-on course, Digital Communication: Part II—Optimizing System Performance.
Participants receive the text Digital Communications: Fundamentals and Applications, 2nd Edition, Bernard Sklar (Prentice-Hall, 2001) and lecture notes on the first day of the course. These notes are for participants only and are not for sale or unauthorized distribution.
Coordinator and Lecturer
Bernard Sklar, PhD, President, Communications Engineering Services, Tarzana, California. Dr. Sklar was previously at The Aerospace Corporation and has acquired over 50 years of experience in the electronics industry in a wide variety of technical design and management positions. He has worked at Republic Aviation Corporation, Hughes Aircraft Company, and Litton Systems, and has taught communications at both the University of Southern California and UCLA. He is currently associated with the University of Cape Town, South Africa as an external examiner. He also has taught at other universities and has presented numerous short courses throughout the United States, Europe, and the Far East. Dr. Sklar has published and presented scores of technical papers, is the recipient of the 1984 Prize Paper Award from the IEEE Communications Society for his tutorial series on digital communications, and is the author of Digital Communications: Fundamentals and Applications, Second Edition (Prentice-Hall, 2001). He is a past chairman of the Los Angeles Council IEEE Education Committee.
Data Encoding and Baseband Transmission
Digital vs. analog performance; spectral density and autocorrelation; noise in communication systems; bandwidth requirements for digital data; sampling, quantization, and PCM coding; and intersymbol interference and pulse shaping.
Bandpass Modulation and Demodulation
Coherent and noncoherent detection of signals in Gaussian noise; PSK, DPSK, QPSK, FSK, ASK, and APK signaling—a geometric view; correlators and matched filters; detection theory; M-ary signaling: orthogonal vs. multiple phase signaling; and bit error vs. symbol error probability.
What the System Link Budget Tells the System Engineer
Sources of loss and noise; EIRP, G/T, antenna gain, path loss; why is free-space loss a function of wavelength; how much margin is enough?; where in the system is Eb /N0 defined; where can it be modeled?; two Eb /N0 values of interest; noise figure, noise temperature, antenna temperature, system temperature; when does improved noise figure translate into improved SNR and when does it not; and a training exercise in link constraints.
Channel Coding: Error Detection and Correction
Code rate, coding gain, vector spaces, and sub-spaces; linear block codes, generator, and parity check matrices; syndrome calculation, code capability, and erasure correction; cyclic codes and their algebraic structure; shift register encoding and decoding; convolutional coding, hard vs. soft decisions, Viterbi decoding algorithm, and how it finds the maximum-likelihood sequence; computer demonstration of coding principles; interleaving for channels with memory; Reed-Solomon codes; and concatenated codes.
Defining, Designing, and Evaluating Systems
A systematic approach for meeting bandwidth- and error-performance requirements; criteria for choosing signaling schemes for bandwidth-limited systems and power-limited systems; the subtle computations encountered when transforming from data-bits to channel-bits to symbols to chips; and the step-by-step approach used for evaluating almost any digital communication system.
Key design goals and constraints; system trade-offs; how to choose error-correcting codes that best match the channel; training exercise illustrating system trade-offs in the areas of modulation and coding; and why do traditional error-correcting codes yield error-performance degradation at low values of Eb /N0?
Multiple Access and Spread Spectrum
How to efficiently share resources among multiple users; FDMA, TDMA, CDMA, multiple access for wireless applications; spread-spectrum attributes; PN codes, feedback shift registers; direct sequencing; frequency hopping; tools to protect against intentional or accidental interference, processing gain; why spread-spectrum techniques can’t be used for improving error performance in channels degraded only by AWGN; and a training exercise in spread spectrum design.
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