Currently, mobile radio systems are the fastest growing segment of the radio market. Microminiaturization of analog microwave chips and the introduction of microprocessors have qualitatively changed the radio equipment, it has become not only a means of special and professional purpose, but also a means of communication of the mass consumer. Mobile radio communication systems are complex complexes that include fairly independent components: radio channel, speech transformation, noise-resistant coding and encryption, frequency-territorial planning, etc. d. The basis of the functioning of the modern radio communication system is the radio channel of digital data transmission .. The method of forming the spectrum of signals, the type of modulation, the circuit of the receiver of high-frequency modulated signals, the recovery algorithm of the transmitted digital message determine the main operational characteristics of the radio communication system. number of communication channels in the allocated frequency band, speed of information transmission, reliability and quality of information reception. This book consistently outlines the main ideas and technical solutions that form the basis of digital data transmission over a radio channel, and the operation of the radio channel as part of a radio communication system. In the second edition, the shortcomings and inaccuracies were corrected, sections devoted to the peculiarities of the propagation of radio waves in the city, optimal reception and synchronization were significantly expanded. For undergraduate students studying in infocommunication and radio engineering specialties, it can be useful for graduate students and engineers working in the field of digital radio communication networks.