飛行実験による航空衛星データ通信の伝送誤り特性測定

抄録

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 measured results of C/N₀ (ratio of carrier power-to-noise density) variations, transmission errors in various flight and link conditions, and the properties obtained by analysis of measured results. Then, we compared the resultant BER characteristics with those obtained by simulations for various values of C/M (carrier-to-multipath power ratio). We found that the BER characteristics of P-channel BPSK with forward error correction (FEC, convolutional coding/Viterbi decoding with interleaving) are equivalent to those for C/M of 8 dB when an elevation angle is about 10 degrees, and to that for C/M of 5 dB when an elevation angle is less than 5 degrees. We found that the BER characteristics degrade if the aircraft attitude (roll angle) changes considerably even when an elevation angle is fairly high. We also found that the BER characteristics of T channel are a little worse than those of P channel.