The field of companies hoping to build a high-speed data network in the sky is even more crowded after Orbital Sciences Corp. announced today that it has applied for an FCC license to build and operate a global satellite network.
The network, Orblink, will use seven medium-Earth-orbit (MEO) satellites to provide a number of broadband services worldwide, including Internet access, email, video conferencing, and electronic commerce. The satellites will sit 9,000 kilometers above Earth, stretching out along the equator - a position that will allow Orblink's service to blanket the globe, said Joe Bravman, Orbital's senior vice president.
MEO also made logistical sense for Orblink. "GEO satellites take more power and leave you with a significant time delay for classes of services," explained Bravman. Using a low-earth-orbit (LEO) system such as Teledesic's, which will launch 288 satellites plus spares, to form a network that resembles a geodesic sphere, seemed too complex to achieve their goal, he added.
Orblink has applied to use two bands of the millimeter wave spectrum 37.5 to 38.5 GHz and 47.7 to 48.7 GHz to offer direct two-way connections over which it plans to offer transmission rates of 1.5 Mbps for downlinks and 1.25 Gbps for uplinks.
A key part of Orblink will be its inter-satellite communication system. The company wants to use another slice of the millimeter wave spectrum 65.0 to 71.0 GHz to route data between satellites at a rate of 15 Gbps. A simple switching system onboard each satellite will either turn around an uplink and route it down to its destination, or route it across its spacebound RF communications ring to a satellite over the appropriate geographic region.
"We didn't put any sophisticated routing or switching onboard, because that would drive up the cost of the satellites," Bravman said.
By contrast, each Teledesic satellite has "connectionless" links with its eight neighboring satellites. Each satellite acts as a switch in this mesh network, and all communication within the network is treated as streams of short, fixed-length (512 bits) packets. The network uses mechanisms similar to Asynchronous Transfer Mode (ATM), a method widely used in local-area networks. Through these connections, Teledesic said it can transmit data at a rate of 155.52 Mbps between satellites.
Although Orblink and Teledesic operate in different spectrum bands and through different orbits, they are planning to offer many of the same services – in the same time frame. Orblink said it plans to start launching its satellites in 2001 and begin service in 2002.
