Examining the topic from both a theoretical and practical perspective, this book covers a wide variety of topics in digital communications. Notable features include expression of the probability of error in terms of the Euclidean distance instead of the usual EbIN0 adoption of a new approach to the Viterbi algorithm that does not assume any knowledge of the encoder starting and ending states, discussions on constellation shaping, shell mapping algorithm and root-raised cosine pulse shaping, and a unified approach to continuous phase frequency modulation where M-ary FSK and MSK are special cases. The book is well suited for a senior undergraduate to a graduate level course in communications theory. The accompanying CD-ROM containing C programs on Viterbi algorithm, shell mapping and turbo codes will aid the student in understanding these topics better.