Researchers Continue to Examine HPWREN Connectivity Between Ground Station and Airplane

UCSD and SDSU researchers recently collaborated for a high performance data communications demonstration involving a research airplane and a ground station. The experiment is the second in a series of multiple tests that evaluate the use of radios that communicate using the unlicensed spectrum with a nearby airplane.

While the first test used a tripod-mounted, manually-steered yagi antenna, the most recent test used this stationary set of planar array antennas that pointed vertically to reach the airplane. One of the ground station antennas, which were both connected to the same radio, provided an additional link to an HPWREN backbone node atop Mount Woodson and finally onto the San Diego Supercomputer Center, where the HPWREN backbone originates.

"During the April test we manually tracked the airplane from the ground, with ground antennas mounted on a tripod. This yielded excellent results, but the tracking was messy - primarily due to multiple cables that often entangled," explains Hans-Werner Braun, HPWREN principal investigator. "In this second test, we used a stationary antenna on the ground with no manual steering. Expectedly, this yielded worse connectivity results because (a) the antennas were not explicitly trained onto the airplane, and (b) the flying was (purposely) not very well defined (including lots of banking and flying out of reach), to learn more about the border conditions."

Braun says that the third test, which will take place later this fall, will repeat the same setup as this second test. However, the researchers will next work with defined flight patterns that specifically support the area underneath the airplane.

A second objective of the test was to remotely control a digital camera located on the airplane. This image illustrates a photograph of the Ramona area that was snapped via the airborne digital camera - by a researcher located at the ground station.

A third objective of the experiment was to utilize the ground station to:

• provide data connectivity to the radio on the plane;
• provide local wireless connectivity close to the ground station;
• provide for a direct link to an HPWREN backbone site on a mountain top; and
• test the radios in an air-ground environment

These four goals were accomplished with a single ground station radio, connected via signal splitter to multiple antennas. Specifically, the USR2450 radio was equipped with Linux software, which allows for Ethernet-Ethernet bridging with topology discovery for point-to-multipoint links - while simultaneously functioning as an access point.

The demonstration's wireless package was architected and installed by Pablo Bryant, a research technologist from San Diego State University's Field Station Programs. "The wireless package is comprised of a US Robotics Access Point, a 20dB external amplifier, planar array antenna, and two 12 amp-hour 12VDC batteries," explains Bryant. "This current design is about a foot shorter that the first design because of the new antenna, and this allows enough space for a passenger in the rear seat."

Participants in the demonstration included Rommel Zulueta, an SDSU doctoral student and the airplane pilot; Hal Holmerud, Outreach Administrator for the Crisis/Consequence Management Initiative at the SPAWAR Systems Center San Diego; Todd Hansen, systems coordinator for the NSF-funded ROADNet research project; Bryant; and Braun.

Additional photographs documenting the demonstration, as well as images taken of the nearby Pines Fire, are available at /Photos/20020807/.

Details regarding the first test, which was conducted in April, are available at /news/020430.html.

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