Utilizing Satellite Communication to Enable Robust Future Flight Data Links

Path propagation losses play a vital role in the communications system design. During a commercial flight, passengers can be connected to the internet via earth stations or satellites, depending on the longevity and location of the flight. For long distance flights, particularly over sea, connectivity via satellites has practical advantages over ground stations. Many communication satellites reside in geostationary orbit which cannot provide connectivity to the poles. However, data indicates there is a disproportionate quantity of commercial flights operating in the northern hemisphere, and it is known that the strength of the link to a geosynchronous communication satellite will decrease with distance from the equator. Therefore, a link has been simulated between the Inmarsat GX 1-5 GEO satellites operating in the Ka-band and a commercial aircraft. It has been observed that longitudinal location of the aircraft on the globe has little effect on the strength of the link at the cruise altitudes of commercial aircraft (11km), where the aircraft is flying above rain cloud height of approximately 4km. When analysing GX 1-4 satellites we find these cruising altitudes provide an operable link of up to a latitude of 48°, with the link failing at 65°, largely independent of longitudinal position. At altitudes below rain height, atmospheric attenuation has a significant impact on the link, varying with global position, and resulting in insufficient links at any global position. In comparison when viewing the GX-5 VHT satellite we find that below 2km there is high variation in the Carrier-to-Noise (C/N) ratio dependant on latitude, however as altitude increases, a constant link is obtained with only slight link degradation shown as we move through the GX-5 operational sphere.