The book focuses on the advanced mmWave/Sub-terahertz ultra-massive MIMO wireless communications, which are regarded as a promising paradigm shift in future 5G beyond and even 6G. This is achieved by providing a comprehensive review of the rapidly developing field of massive MIMO communication, in-depth discussions on the impact of extremely large-scale antenna array, and detailed numerical simulation results on our proposed schemes. Several case studies are given after introducing basic communication system components, and the simulation codes are open sourced in our book, which shows the reproducibility of our models and methods and provides convenience for readers such as researchers, engineers, and graduate students in the fields of wireless communications.