Digital Communications: Theory, Techniques and Applications is written for students of both undergraduate and post-graduate degree programs in engineering for a course on digital communication. In the first four chapters the book builds the theoretical background necessary to understand the principal ideas of digital communication systems. Thereafter, the book in chapters 5 through 9 discusses the core concepts such as digital coding, multiplexing and multiple access, digital modulation, demodulation and detection. The last chapter of the book discusses the applications of digital communication in the domains of satellite, optical and wireless communication systems. Heavily illustrated with more than 500 figures to help understand and relate to theoretical concepts better, the book also provides graded solved problems, challenging review questions, and numerical exercises for the practice.