Transmission Delay Characteristics of Aeronautical Satellite Data Communication in Flight Environment

Abstract

Satellite data communications have been introduced in some areas to provide the means for message exchange between air traffic controller and pilot, and for aircraft surveillance in oceanic areas. Before the completion of the standards on aeronautical satellite data communication by the International Civil Aviation Organization (ICAO), we had conducted a series of flight experiment using INMARSAT satellites to validate the draft standards being developed by ICAO. In the flight experiments, we evaluated the characteristics on radio propagation, transmission error, Automatic Dependent Surveillance (ADS), etc. This report describes the transmission delay characteristics measured in flight environment for various satellite link conditions. Since Controller-Pilot Data Link Communications (CPDLC) and ADS call for reliability and swiftness in data transfer, the transmission delay is an important parameter. Especially, it is very true in ADS, because it affects the surveillance performances. Larger transmission delay leads to larger position extrapolation error. We clarified the transmission delay characteristics for various conditions of C/N₀, satellite elevation, etc. We also showed the mechanism in which data transfer delay increases.