Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

In the late 1990s, a scramble to provide high-speed Internet access resulted in a number of strategies and technologies. These included the now well-established DSL and cable modem access methods, as well as some sideshow technologies such as access over electric power lines (which mostly failed). Satellite constellations were also deployed, but perhaps the most interesting were the flying/floating platforms called HALOs (High Altitude Long Operations).

HALOs offer network access services by providing communication platforms flying in the stratosphere above cities. The platforms provide uplink and downlink transmissions much like satellites, except that they are closer to Earth. The signal propagation times are shorter and the platforms stay over a particular area. HALOs are a good choice for enterprise Internet access. They provide data rates as high as 10 Mbits/sec. Two companies are involved in this business, both offering a different platform:

• Angel Technologies    This company flies airplanes above metropolitan areas and provides symmetrical service and Internet access up to 10 Mbits/sec. In the U.S., Angel's services operate in the LMDS (Local Multipoint Distribution Service) microwave ranges of 24 GHz, 28 GHz, and 38 GHz. In other countries, the 3- to 20-GHz range may be used. The airplane is similar to a corporate jet. It flies 10 miles above the target area in a 2.5-mile- diameter circle. The ground coverage area is up to 75 miles in diameter. Planes fly three shifts of 8 hours each. The 40-kilowatt signal is powered by the jet engines and can penetrate weather conditions normally adverse to microwaves. Angel is working with Raytheon for the communication link and with several companies that have pioneered high-flying, long-duration aircraft.


• Skystation International    Skystation has designed unmanned helium-filled blimps (the company prefers to call them "vehicles" or "aerostats") that can be used for a variety of applications, one of which is telecommunications/Internet access. The platform was also designed to be used for earth sciences applications. For communications, the platforms can maintain geostationary positions. The platforms may be moved around for earth sciences applications. It provides data rates of 2 Mbit/sec on the uplink and as high as 10 Mbits/sec on the downlink. Skystation uses spectrum in the 47-GHz band, which has been designated by the ITU and the FCC for use by high-altitude stratospheric platforms. The life expectancy is estimated to be up to 10 years.

You are not alone if you are somewhat skeptical at these proposals, but the ITU and FCC have already designated a frequency band for such platforms. Also, if you read the white papers at the company Web sites listed on the related entries page, you will see that these schemes are well thought out and practical. The HALO network supports hundreds of thousands of broadband end users on a metropolitan distance scale. Since HALOs are situated high in the sky, they have access to nearly all rooftops within a city.

Proponents of these systems see the emergence of a "stratospheric communication layer" that may trigger a decline in the use of communication satellites. Skystation sees its platforms as being used to provide telephony for developing countries.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
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