Rain attenuation statistics useful for the design of mobilesatellite communication systems

摘要

We have investigated how rain attenuation statistics, necessary tondesign fixed satellite systems working at frequencies greater than 10nGHz, are transformed to those applicable to the design of mobilensatellite systems working in the same frequency bands and weathernconditions in the special case of vehicles driven in zig-zag patterns tonsimulate city streets. The vehicles' speed has been modeled as anlognormal random variable, a mathematical model derived fromnmeasurements performed in freeways or in city traffic. We have used anlarge number of rain-rate time series collected in Italy (Gera Lario andnFucino) and in Canada (Montreal) to simulate rain-rate spatial fieldsnand radio links at 19.77 GHz along a 30.6° slant path. Thensimulations have shown that a receiving or transmitting terminal movingnin zig-zag patterns may experience, in the long term and for a givennattenuation, a smaller outage probability, compared to the fixednterminal. For a given rain attenuation, the ratio between the outagenprobability of the mobile system and that of the fixed systemn(probability extrapolation factor Ξ) is estimated to be aroundn0.2-0.3 in the optimistic case in which the probability of encounteringnrain is the same for all observers (fixed or in motion)-a lessnoptimistic estimate shows that the probability of encountering rainnmight be twice as large and that, as a consequence, the values of Ξnmentioned must be doubled. Conservative values of Ξ can be calculatednby using average values of rain storm speed and vehicles and averagendistances covered in the rain by fixed and mobile terminals. The resultsnare less sensitive to changes in the geometrical or other parameters ofnthe simulations