This text provides an introduction to the analysis and design of digital communication systems. The third edition has been updated with a discussion of modern technological advances, providing coverage of such topics as digital modulation and demodulation techniques, source coding, channel coding and decoding, spread spectrum signals, channel equilization, multiuser communications, and modulation and coding for fading multipath channels. In addition, the book has been reorganized so that each chapter builds on previous material, begins with an introduction to the history and classification of channel models and reviews important topics in probability and stochastic processes.