Iridium is targeted at telephone users located in odd places. Our next example, Teledesic, is targeted at bandwidth-hungry Internet users all over the world. It was conceived in 1990 by mobile phone pioneer Craig McCaw and Microsoft founder Bill Gates, who was unhappy with the snail's pace at which the world's telephone companies were providing high bandwidth to computer users. The goal of the Teledesic system is to provide millions of concurrent Internet users with an uplink of as much as 100 Mbps and a downlink of up to 720 Mbps using a small, fixed, VSAT-type antenna, completely bypassing the telephone system. To telephone companies, this is pie-in-the-sky.
The original design was for a system consisting of 288 small-footprint satellites arranged in 12 planes just below the lower Van Allen belt at an altitude of 1350 km. This was later changed to 30 satellites with larger footprints. Transmission occurs in the relatively uncrowded and high-bandwidth Ka band. The system is packet-switched in space, with each satellite capable of routing packets to its neighboring satellites. When a user needs bandwidth to send packets, it is requested and assigned dynamically in about 50 msec. The system is scheduled to go live in 2005 if all goes as planned.
The original design was for a system consisting of 288 small-footprint satellites arranged in 12 planes just below the lower Van Allen belt at an altitude of 1350 km. This was later changed to 30 satellites with larger footprints. Transmission occurs in the relatively uncrowded and high-bandwidth Ka band. The system is packet-switched in space, with each satellite capable of routing packets to its neighboring satellites. When a user needs bandwidth to send packets, it is requested and assigned dynamically in about 50 msec. The system is scheduled to go live in 2005 if all goes as planned.