Principles of Communication provides an introduction to the fundamental principles of communications. Basic mathematical background for system and signals, analog communication systems, and modern digital communication systems are systematically introduced. Principles of Communication theory is been explained in an easy-to-understand way. Advanced topics in modern digital communications, especially related to wireless communications, have been conceptually explained, including forward error correcting codes, fading channels, OFDM, and CDMA. This book serves as the basis of communication system design, and as a way to quickly understand the principles of communication systems for those who do not major in communications. Its readership includes undergraduate a graduate level students in the field of Communications and research engineers at Communications companies.