Delay Doppler Communications and Sensing: Principles, Advances and Applications of OTFS provides a comprehensive exploration of the principles and cutting-edge developments of delay Doppler (DD) communications and sensing with a specific focus on the advances and application of orthogonal time frequency space (OTFS). It highlights the fundamental theory for DD communications and sensing through the Zak transform, and discusses how this classic concept from quantum physics can reshape modern wireless technology. The important aspects of DD communications and sensing are introduced in detail, including transceiver design, performance analysis, and its application. In particular, this book reveals the intrinsic connections between DD domain wireless communication and sensing channels, unveiling the important interplay between communication and sensing functionalities in the DD domain. The book introduces the principles and design of communications and sensing based on the DD signal processing framework as well as delving into advanced aspects, such as DD domain MIMO and DD domain integrated sensing and communications (ISAC). By providing a comprehensive overview of both fundamental principles, cutting-edge research and practical applications, this book gives a deep understanding of the underlying concepts and techniques in Delay Doppler (DD) communications and sensing. With this book the reader will: Gain a comprehensive understanding of the Zak transform and DD domain wireless channels Understand the concept of DD communications, including the popular variants of OTFS Learn implementation details of DD communications and sensing Follow state-of-the-art developments in DD communications and sensing Grasp the insights and physical interpretations of DD communications and sensing Have access to programming codes for OTFS and DD communications and sensing.