Bandwidth from above

New satellites form beams dynamically for point-to-point, high-capacity communications

Hughes Network Systems is preparing to bring online a new generation of data communications satellites that will be able to provide higher bandwidth and more service options to the ground.

The Spaceway 3 is the first commercial data service satellite with onboard processing and routing to enable point-to-point mesh communications rather than the hub system now used. New antenna technology directs downlink signals in narrow beams so that the same frequency can be reused in more channels.

Quantum increase

'We can drive a lot more bits through the same amount of spectrum,' said Hughes Senior Vice President Mike Cook. The Spaceway 3 has a total capacity of about 10 gigabits/sec, seven to 10 times the capacity of current satellites.

Uplink speeds from the very-small-aperture terminal (VSAT) used to connect to the satellite are about 2 megabits/sec.

Total capacity of a downlink carrier beam is 440 megabits/sec, which is shared by the VSAT terminals within that beam. Maximum downlink speeds per user probably will be on the order of 10 to 15 megabits/sec.

Dynamic beam formation from the satellite will allow capacity to be directed where it is needed, Cook said. 'We can deliver bandwidth on demand to the ground.'

Hughes has its roots in the retail point-of-sale market, and most of the nation's gasoline credit-card charges are authorized through a Hughes system.

The system is a low-bandwidth application, but as demand for capacity grew, the company began looking for better ways to deliver bandwidth from space.

Current communications satellites basically are repeaters that reflect a signal back to Earth in a large footprint that covers most of the country. This is fine for broadcasting but can be inefficient for individual data users and requires a ground station hub to receive and deliver data to a user's data center or network.

The Spaceway system was developed with Boeing Satellite Systems International and is based on the company's 702 satellite platform. An onboard processor demodulates the signal so that IP packets can be examined. An onboard router reads the destination, and a phased-array antenna forms a beam to carry the signal to the appropriate terminal.

The satellite, which will sit in a geosynchronous orbit above the equator at 95 degrees west longitude, will cover the entire continental United States, Hawaii and Alaska, but individual beams will have a footprint of only about 100 kilometers ' which is narrow for a signal coming from an altitude of 22,300 miles.

Spaceway operates in the microwave Ka-band, which allows it to deliver more bits to smaller antennas. Coupled with the dynamic beam formation, that allows point-to-point communication.

'We can send the data from any small disk to any other small disk' without going through a ground station, Cook said.

Weather response

These features will let Hughes prioritize traffic and offer quality-of-service and service-level agreements. Government, along with Hughes' enterprise customers and remote consumers not on cable or DSL grids, are primary markets for the new service, and the company is talking with a number of agencies.

Spaceway 3 was launched in August and is moving toward its final orbital position. Systems testing is expected to begin this year, and the target date for commercial service is the first quarter of 2008.

Because the Ka-band signal is more susceptible to interference from rain than the lower-frequency Ku band, dynamic weather radar feeds let the satellite determine conditions on the ground and adjust signal power accordingly.

As its name implies, Spaceway 3 has two older siblings, but through a series of corporate acquisitions and spinoffs, they now belong to DirecTV. They are functionally the same as Spaceway 3 but have been tweaked by the satellite TV company to deliver high-definition programming within local market areas.

About the Author

William Jackson is a Maryland-based freelance writer.


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