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SATELLITE

Communication satellites are, in effect, orbiting microwave relay stations, located about 35,000 km above the surface of the earth, used to link two or more earth-based microwave stations. Communication satellite providers typically lease some or all of a satellite's channels to large corporations, which use them for long-distance telephone traffic, private data networks, and distribution of television signals. Leasing these huge communication "pipes" can be very expensive, therefore they are not suitable for the mass residential marketplace. Consequently, a new suite of services, called the direct broadcast satellite (DBS) system, has been developed to provide consumers with a range of high-speed Internet access services.

A DBS system consists of a minidish that connects in-home networks to satellites with the ability to deliver multimedia data to a home network at speeds in excess of 45 Mbps. This speed can only be achieved when downloading content, however. To upload or send information to the Internet, the system uses a slow telephone connection. Satellite systems normally use the Quadrature Phase Shift Keying (QPSK) modulation format to transmit data from the dish in the sky to the minidish on the roof.


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