This textbook provides a concise but lucid explanation of the fundamentals of spread-spectrum systems with an emphasis on theoretical principles. The choice of specific topics is tempered by the author's judgment of their practical significance and interest to both researchers and system designers. Throughout the book, learning is facilitated by many new or streamlined derivations of the classical theory. Problems at the end of each chapter are intended to assist readers in consolidating their knowledge and to provide practice in analytical techniques. This third edition includes new coverage of topics such as CDMA networks, Acquisition and Synchronization in DS-CDMA Cellular Networks, Hopsets for FH-CDMA Ad Hoc Networks, and Implications of Information Theory, as well as updated and revised material on Central Limit Theorem, Power Spectral Density of FH/CPM Complex Envelopes, and Anticipative Adaptive-Array Algorithm for Frequency-Hopping Systems.