Abstract: The past 30 years have witnessed the introduction andphenomenal improvement of digital communicationsservices. Several characteristics emerge when lookingat the trends. First, capacity and capability ofcommunications networks are growing rapidly. Next,local and personal access to digital services isexpanding. Finally, ordinary 4 kHz analog voice linesare now providing 28.8 kbps digital services in thehome. Only 15 years ago, this data rate was 300 bps, agrowth factor of 96 in 15 years or 36 percent per year.In addition, clever data compression techniques havereduced the data rates required for speech and video,and we now have the ability to provide videoconferencing on computers using existing terrestrialnetworks. As the world makes greater use of wirelesscommunications, hundreds of satellites are orbiting inspace to provide fixed and mobile services. Because ofthe large number of satellites, the geostationary orbitis heavily used. More sophisticated satellites could bedesigned, but a simpler solution is to move to higherfrequencies offered by millimeter wave bands. Dozens ofUS companies are currently developing systems that willprovide high data services to the world. !0
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