Abstract: The past 30 years have witnessed the introduction and phenomenal improvement of digital communications services. Several characteristics emerge when looking at the trends. First, capacity and capability of communications networks are growing rapidly. Next, local and personal access to digital services is expanding. Finally, ordinary 4 kHz analog voice lines are now providing 28.8 kbps digital services in the home. Only 15 years ago, this data rate was 300 bps, a growth factor of 96 in 15 years or 36 percent per year. In addition, clever data compression techniques have reduced the data rates required for speech and video, and we now have the ability to provide video conferencing on computers using existing terrestrial networks. As the world makes greater use of wireless communications, hundreds of satellites are orbiting in space to provide fixed and mobile services. Because of the large number of satellites, the geostationary orbit is heavily used. More sophisticated satellites could be designed, but a simpler solution is to move to higher frequencies offered by millimeter wave bands. Dozens of US companies are currently developing systems that will provide high data services to the world. !0
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