"Research and development in the context of 6G wireless communication is now in its early stages. 6G research, standardization, and implementation efforts will constitute a major driving force both in the academia and in the industry through the next five to ten years. Several new use-cases are expected to play a central role in 6G compared to previous generations giving rise to new type of requirements which render contemporary physical layer waveforms such as CDMA and OFDM inadequate. Two key such use cases are communication under high Doppler spread arising from high mobility such as high-speed train and airplane connectivity and communication in intelligent transportation systems such as V2V/V2X. The new requirement in the first use case is performance robustness to high Doppler spread. The new requirement in the second use case is radar sensing capability. Both requirements are not adequately accounted for by contemporary waveforms. The OTFS waveform naturally accounts for the requirements in both use cases while maintaining equivalent or superior performance in traditional use cases as well. The academic research on OTFS has been growing exponentially in the past five years and also the interest from the industry and the community at large - clearly marking the need for a good textbook on the topic. What is needed is a book that lays the theory ground up and discusses the applications. Two key aspects of the OTFS communication paradigm are: 1 - channel representation in the delay-Doppler domain and 2 - signaling of information in the delay-Doppler domain. Both these aspects stand in sharp contrast with conventional multi-carrier communication paradigm where both channel representation and information signaling are carried in the time-frequency domain. In this regard, OTFS constitutes a fundamental paradigm shift in communication theory, moving it away from traditional time-frequency signal processing to delay-Doppler signal processing."-- Provided by publisher.