SkyTower, in collaboration with the Japan Ministry of Telecommunications and NASA, said it successfully completed a series of commercial telecommunications tests from more than 65,000 feet in the stratosphere.

The tests, which began three weeks ago, were conducted from Pathfinder-Plus, the aircraft developed by AeroVironment, the parent company of SkyTower. Both companies are based in Monrovia, California.

12-Mile-High Cell Tower

From a position over the island of Kauai, Hawaii, Pathfinder-Plus transmitted several hours of next-generation mobile voice, data and video services to multiple handheld devices on the ground, SkyTower said. The airborne platform was described as the equivalent of a 12-mile-tall cell or broadcast tower.

Following a test of what SkyTower claimed was the world's first digital high-definition television (HDTV) broadcast transmission from the stratosphere, an IMT-2000 (third-generation, or 3G) mobile communications trial was conducted from the platform. The exercise demonstrated a wireless video broadcast using an off-the-shelf NTT DoCoMo handset, along with Internet surfing on a wireless modem-equipped laptop at data speeds of up to 384 kbps.

The company's first deployment, fixed wireless infrastructure , should be available within three years, according to Stuart Hindle, vice-president of strategy and business development at SkyTower.

While the solar-powered aircraft currently lands at night, Hindle said the company is developing a fuel-cell energy storage system that will allow flights of up to six months in duration.

Spectrum Efficiency

Because of its higher angle, the SkyTower platform can fill the gaps in dense urban coverage areas missed by terrestrial and satellite broadcast transmissions due to tall buildings or terrain, using a fraction of the power .

The SkyTower platform connects users within its footprint of 30 to 600 miles in diameter to gateways on the ground that are linked directly into a central switch/fiber optic backbone. The system can be deployed by service providers at a fraction of the cost for DSL or cable broadband systems, said Hindle.

With a closer proximity to earth, SkyTower enables higher-frequency reuse than satellites, resulting in some 1,000 times the local access capacity, compared to a geostationary satellite. Multiple stratospheric platforms can serve the same area, further reusing the same frequency spectrum and multiplying system capacity. The basic footprint for fixed broadband is a 50-mile radius, Hindle said.

The ROI Challenge

The SkyTower platform would best be used in limited coverage environments, Yankee Group analyst Phil Marshall told Wireless NewsFactor. He said the ability to traverse a range of technologies -- such as 3G mobile communications, fixed broadband, narrowband and direct broadcast -- make it a compelling proposition.

But, said Marshall, the company faces hurdles in ensuring it can implement the platform at a reasonable cost, deliver the capacity required to support a subscriber base, and draw a sufficient number of customers to justify a return on investment.

Another potential problem, he said, is that the platform must find find the optimum location to serve a number of different technologies.

"It may be a great concept, but without capacity and demand it is not a viable technology," Marshall said. He noted that the Iridium low-orbit satellite network has run into problems meeting those same challenges.

A consortium of Japanese manufacturers, including NEC and Toshiba, developed the communication systems carried by Pathfinder-Plus for the recent tests.