Advances in Communication Systems: Theory and Applications, Volume 3 focuses on feedback systems, data compression, satellite communications, decoding techniques, and synchronization. The selection first elaborates on sequential signal design for channels with feedback and adaptive data compression for video signals. Discussions focus on theory and application of an adaptive compression system, feedback systems with an average power constraint, and a time-continuous binary system with peak and average power constraints. The text then ponders on the aspects of communications satellite systems, including communications satellites and modulation methods. The manuscript takes a look at advances in threshold, signal design problem of coding and synchronization, and progress in sequential decoding. Topics include Wozencraft sequential decoding algorithm, phased-locked loop approach, rapid acquisition sequences, and optimality of the square-wave correlation function for the first-order loop. The selection is a vital source of data for researchers interested in feedback systems, satellite communications, synchronization, and decoding techniques.