2006 UPDATE

It is February 11, 2006, a dozen years after I wrote the little paper titled:
"A DATA LINK FOR COLLISION AVOIDANCE, PRECISION LANDING APPROACHES, AND COMMUNICATION"

Something exciting has happened.  The Universal Access Transceiver (UAT) is a production device that can actually be purchased from Garmin for $8000.

The Garmin GDL 90 UAT (CACHED) contains a GPS receiver, a single channel transceiver using simple two frequency FSK (Frequency Shift Keying) modulation, and, I presume, the necessary packet processing capability to do the job I described in my paper.

From bits and pieces I have gleaned from the WEB, I believe it is a result of the FAA Capstone ADS-B (CACHED) experiment in Alaska.  I am guessing that the Apollo-Tomorrow Company designed it for the FAA.  This Salem, Oregon company was purchased by Garmin of Olathe, Kansas and is now called Garmin AT.

The link frequency of 978 MHz lies in the internationally accepted aircraft Distance Measuring Equipment (DME) frequency range of 962 to 1150 MHz.  The FAA already owns this spectrum.  I proposed stealing one of the UHF television channels which could have been difficult.

The use of the DME band did not occur to me in 1994.  It seems so obvious now.  DME was an important piece of the cockpit in 1994.  Today, we use the vastly superior GPS for distance and speed.
The FAA has verified that the UAT link and DME can co-exist (DME and UAT interference) (CACHED).

The system uses simple binary FSK modulation that provides the advantage of FM Capture Effect (see my paper).  I proposed simple error detection.  The UAT apparently employs Forward Error Correction (FEC) in the form of Cross-Interleaved Reed-Solomon Coding (CIRC) (CACHED) that has been used with great success in both optical and magnetic disk drives.  This coding adds little hardware costs or software overhead and impressively corrects both burst and random errors.

Hundreds of these transceivers have been installed in aircraft and the FAA has installed Ground Based Transceivers (GBT) in Alaska and the East coast.  The GBT's provide realtime, graphic, weather uploads and traffic based on conventional radar sitings.  See AOPA magazine articles (CACHED).
China is implementing the system using the Garmin hardware.  See this.

More than ever, I believe that the GPS approach (ADS-B, Freeflight, etc) will provide enormous efficiency and safety benefits to all of aviation.  I wish we had a national priority with an implementation plan and timetable.

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