An Introduction to Digital Communications focuses on the central theoretical and practical issues involved in modem design. It is intended for a two semester course at the graduate or advanced undergraduate level. The first half of the book deals with the basic issues of baseband and passband data transmission and contains descriptions of applications to specific digital transmission systems. The second half is more specifically addressed to design issues including timing and carrier recovery, channel characterization, adaptive equalization, and trellis coding. Although application oriented, the text is sufficiently rigorous to provide an entry point into current research.