An analysis of results obtained on an aircraft data link out to 1300 nautical miles (2400 km)

An analysis is given of results from an experimental transmission of data on h.f. from an aircraft flying across the Atlantic during the year 1963. Dummy messages were transmitted from the aircraft for two-minute periods every fifteen minutes on about forty-two crossings. The procedure adopted in the analysis was to simulate various coding and error detection systems by means of computer programs and to apply these to the recorded data. By this means an estimate could be made of the relative merits of the various systems in affording protection against the interference and signal mutilation that were experienced during the airborne experiment. Four systems have been simulated and in each case it has been assumed that the air-to-ground message will consist of 20 five-bit characters transmitted at 100 bauds. The analysis indicated that, if half of the total channel time were available for air-to-ground messages, a typical flight would have completed an average of 400 to 500 aircraft messages per hour for the range 350 to 1300 nautical miles and at no time would it have taken longer than about sixty seconds to contact an aircraft.