This book delves into the fundamental characteristics, measurement techniques, modeling methods, and theories of wireless channels in mobile scenarios. Unlike wired communication systems, which are more predictable, wireless communication systems are significantly affected by radio propagation and wireless channels. By investigating the mechanisms of wireless channels and measurement techniques, this book aims to better understand wireless communication systems in order to optimize the quality and design of wireless communications. The title covers key topics in the field, including basic theory of radio wave propagation and non-stationary channels, theory and method of time-varying channel measurement, measurement case analysis, wireless channel modeling theory and parameter extraction method, rail traffic channel measurement and modeling, and dynamic modeling and simulation method of time-varying channels. This book is suitable for researchers and students interested in radio wave propagation, wireless channels and mobile communication systems. It can also serve as a useful guide for technical professionals who have a background in mobile communication technology.