Networking in the 21st Century: The Sky's the Limit

NEWS BLOGS FORUMS NEWSLETTERS RESEARCH EVENTS DIGITAL LIBRARY CAREERS

IMMERSE YOURSELF:

Storage & Servers

Networking in the 21st Century: The Sky's the Limit

What's Next
Given the long planning cycles in space, it's not surprising that work is already under way for a Ka-band successor--one with the potential for a bandwidth mother lode. That future is based on the even higher frequency V-band and millimeter wave frequencies pioneered by the Defense Department as part of Milstar. Higher frequency systems also will be used in combination with some Ka-band systems. Already, players like GE Americom (GE*StarPlus), Hughes (Expressway, StarLynx and SpaceCast), Lockheed Martin, Loral (CyberPath), Motorola (M-Star), Orbital Sciences (OrbLink), PanAmSat (V-Stream), Teledesic and TRW (Global EHS Satellite Network) have set out on the long road to V-band that begins with FCC application.
Terms To Kn ow

Error codes: Since TCP/IP can slow transmissions by interpreting noisy satellite links as congestion, new error coding that requires digital signals is now being deployed. Digital compression also benefits satellite transmission.
Footprint: The geographic area covered by a satellite's beam. GEO footprints can encompass a continent or more.
Onboard processing: Newer systems allow transmissions to be stored and then switched to the proper cell or directly to another satellite through intersatellite links.
Bent pipe: A type of earth-to-satellite-to-earth signal relay that does not involve any significant spaceborne processing. Bent-pipe architectures are sometimes referred to as big repeaters in the sky.
Rain fade: Interference with a signal caused by airborne material such as raindrops. Rain fade can be reduced by putting more powerful transmitters on a satellite or using larger specialized antennas on the ground.
Spotbeam: Technology that breaks a single large broadcast ce ll into a honeycomb of smaller targeted cells. Frequency can be subdivided among these cells and reused in nonadjacent cells. Spotbeam cells tend to be a few hundred miles in diameter.

The future--and perhaps it's not so very distant--also holds the promise of airborne satellite alternatives that float (using propulsion systems) or fly above metropolitan areas. These stratospheric systems lack the global ubiquity of satellites, but most have plans to interconnect to satellites or terrestrial systems.
Former Secretary of State Alexander Haig, for example, is a founder of SkyStation, which is making helium-filled, lighter-than-air vehicles to float 22 kilometers above as many as 250 metropolitan areas. This type of vehicle has been used for tasks like measuring ozone-layer depletion. The FCC approved V-band frequencies for the venture--over the protests of several satellite providers--and SkyStation plans to deploy its first system in the year 2000. Each balloon will be as wide as a football field an d almost twice as long. The most important question raised about SkyStation and similar high-altitude plans is how these balloons will retain a constant position when confronted with the force of solar winds, micrometeors and other high-altitude debris. The SkyStation vehicles will apparently be powered by solar cells and rely on a propulsion system to accomplish this task. The communication systems onboard the balloons will provide 2 Mbps on the uplink and 10 Mbps on the downlink, with estimated costs of a few cents per minute. SkyStation's strategy is to ally with existing national providers worldwide for interconnection, and it has already penned 15 joint-venture agreements.
A second high-altitude approach is Angel Technology's Halo Network, which relies on three piloted aircraft (one is a spare) circling in shifts above a metro area at an altitude of 10 to 12 miles. Some interesting names pop up among Halo's investors, including Teledesic founder Ed Tuck. Halo plans to operate in 100 to 300 cities arou nd the world, providing up to 155 Mbps. Monthly pricing is expected to be less than $50 for 1 Mbps. A ground gateway is also part of the $80-million-per-city configuration. Initial service is slated for 2000 to 2001.
Finally, there are at least two, more tentative high-altitude systems apparently just emerging from the research labs. Japan's PTT has completed a study that confirms the feasibility of a 270-meter solar- and fuel-cell-powered unmanned airship and its one-ton communications payload. The study suggests a full-scale prototype between 2001 and 2002.
Another effort, RotoStar, is an unmanned solar-powered heavier-than-air craft that looks like a merged helicopter and dirigible. Silver Arrow's RotoStar was originally conceived for the Israeli military. RotoStar was designed to hover at 70,000 feet for up to six months using solar power to heat argon gas, which powers a thermodynamic propulsion engine. The program, however, is on hold because Silver Arrow could not justify the phase-change materi als development research needed for the vehicle's thermal storage. Apparently development in this area stopped worldwide after the Defense Department halted the Star Wars project.