STUDIES IN DIGITAL COMMUNICATIONS. PART I: FEASIBILITY OF ASYNCHRONOUS MULTIPLEXING. PART II: PERFORMANCE OF HIGH SPEED DIGITAL COMMUNICATIONS OVER TROPOSCATTER LINKS,

摘要

Part I describes experiments and calculations aimed at demonstrating the feasibility of asynchronous time multiplexing for multichannel speech. The work here generally served to elaborate on the theoretical analysis and predictions made previously,and demonstrated them in the laboratory. The experiments tested various aspects of the method,and culminated in a realistic multichannel experiment with extermal coded speech signals. The major feasibility demonstrations were done by using a digital computer with A-D equipment. However,an analog extremal coding system was built in order to demonstrate the equipment simplicity. The work here showed that asynchronous time multiplexing is feasible,under the conditions treated,for systems having as few as 24sources. It was concluded that the advantage of this method over synchronously multiplexed PCM is about 2.7for 100sources,and 2.1and 24sources. Increases in this advantage should be possible with system improvements. The speech quality with this advantage is not distinguishable,with casual listening,from that of the usual PCM. (Author)