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3G Tested at 65,000 feet in the stratosphere
23rd July 2002

SkyTower, Inc., in collaboration with the Japan Ministry of Telecommunications and NASA, successfully completed a series of commercial telecommunications tests - the world's first from more than 65,000 feet in the stratosphere.

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

The solar-electric powered Pathfinder-Plus took off from the U.S. PMRF Naval Base in the morning, climbed to more than 65,000 feet in the stratosphere, and reached its operating station in the early afternoon. From this position over the scenic island of Kauai, Pathfinder-Plus transmitted several hours of next-generation mobile voice, data, and video services to multiple handheld user devices on the ground.

"These tests demonstrate the viability of the SkyTower stratospheric telecommunications platform as an excellent complement, and in some cases alternative, to satellite and terrestrial systems for a broad range of applications," said Stuart Hindle, vice president of strategy and business development, SkyTower. "The airborne platform, operating above the weather and commercial air traffic, is equivalent to a 12-mile-tall tower, which means significant advantages to telecom service providers and broadcasters."

Picture-Perfect Video Broadcast Signal

The first flight successfully tested the world's first digital high definition television (HDTV) broadcast transmission from the stratosphere, providing a picture-perfect video broadcast signal to a fixed receiver on the ground, at twice the resolution of conventional broadcast transmissions.

Because of its much higher look angle, SkyTower platforms can fill in "urban canyons"-coverage areas missed by terrestrial and satellite broadcast transmissions due to tall buildings, terrain, and the like-and can do so using a fraction of the power. During the tests, a 24 Mbps data rate was achieved using only 1 watt of power - less than 1/10,000 the power used by a typical terrestrial broadcast transmitter that has to overcome buildings, trees and other obstructions to cover the same area. SkyTower's local footprint can also help satellite broadcasters overcome capacity challenges that limit their ability to provide local channels within each market.

Low-Cost Wireless Communications Infrastructure

The HDTV broadcast was later followed by an IMT-2000 (third-generation or "3G") mobile test that demonstrated video telephony using an off-the-shelf NTT DoCoMo handset sold in Japan, and Internet surfing from a wireless modem-equipped laptop at data speeds of up to 384 kbps.

"Given the amount of money that wireless service providers have spent on spectrum licenses for both fixed and mobile applications, these SkyTower tests should be of great interest," Hindle said. "Imagine launching a single platform, having instant metropolitan-wide market coverage, and eliminating the terrestrial costs associated with tower build-outs and backhaul."

The SkyTower platform connects users within its footprint of 30 to 600 miles in diameter to one or two gateway stations on the ground that can be tied directly into a central switch/fiber optic backbone. Hindle said, "What this means for business and consumer users is dramatically lower service costs. For instance, SkyTower, based on analyses completed with telecom service providers and system developers, projects that the capital cost per subscriber to deploy a fixed broadband system, including redundant back-up platforms, is a fraction of the cost of other alternatives such as cable, DSL and satellite."

He added that small, low-cost, stationary user antennas can be used due to the unique tight turning radius of the aircraft, which makes it appear geostationary from the ground. The platform's closer proximity to earth enables much higher frequency reuse than satellites, resulting in more than 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, he said.

World Altitude Record Shattered

The Pathfinder-Plus 121-foot wingspan, solar-powered aircraft, is a smaller version of AeroVironment's 247-foot wingspan Helios aircraft which, during NASA testing in Hawaii last summer, shattered the world altitude record for non-rocket powered aircraft by flying to 96,863 feet - well above the 60,000 to 70,000 feet targeted for commercial telecom services. As part of the NASA development program, multi-day flight capability will be demonstrated next year with the Helios solar/electric airplane using the world's first fuel cell based aircraft energy system that enables the aircraft to operate through the night.

Production versions of Helios unmanned aerial vehicles (UAVs) using AeroVironment's fuel-cell-based energy systems will have flight durations between landings of up to six months or more.

SkyTower was formed by AeroVironment two years ago to pursue commercial telecom access advantages enabled by AeroVironment's solar-electric aircraft technology. SkyTower is one of several new businesses launched based on the performance and economic advantages of AeroVironment's breakthrough technologies in the areas of UAVs and efficient energy technologies.

Broadband Battlefield Communications

"In addition to commercial interest in SkyTower's telecommunication infrastructure, there is strong and growing government interest in AeroVironment's UAVs, especially given the current defense needs," said Tim Conver, AeroVironment's chief executive. "Government interest ranges from broadband battlefield communications to emergency backup telecom services."

NASA and AeroVironment have worked together for years in the development of the solar-electric aircraft technology. In September, NASA will be sponsoring an agricultural remote sensing mission, using the Pathfinder Plus aircraft equipped with multi-spectral imaging equipment to conduct several studies including demonstrating how crop yields could be optimized by identifying factors such as the optimal time to harvest, required changes in irrigation levels, and outbreak of crop disease.

The CRL and TAO divisions of the Japanese Ministry of Telecommunications have been leading international advocates of using stratospheric platforms as a low-cost, high-capacity means to make the most efficient use of scarce frequency spectrum. Hindle said they have been instrumental in securing international frequency spectrum allocations for what is now classified by the International Telecommunications Union as High Altitude Platform Stations (HAPS).

With funding from CRL and TAO, a consortium of Japanese manufacturers including NEC and Toshiba developed the communication systems carried by Pathfinder-Plus for the HDTV and IMT-2000 testing and Fuji Heavy Industries integrated the payloads for their stratospheric flights.

SkyTower and AeroVironment have been working closely with domestic and international regulatory bodies to obtain the approvals required to provide telecommunications services from a platform in the stratosphere. Authorization was obtained from the Federal Communications Commission to support the telecom testing this summer, and all flight tests in controlled U.S. airspace are authorized by the Federal Aviation Administration. SkyTower believes that the platform's extremely lightweight and environmentally benign characteristics, combined with its highly efficient use of frequency spectrum and energy, help facilitate favorable regulatory support. SkyTower plans to launch the first commercial service, fixed wireless broadband infrastructure, within three years, and is in advanced discussions with multiple domestic and international service providers interested in SkyTower's revolutionary "last-mile" (local access) solution.

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