Attenuation statistics estimated from radar measurements in MEO satellite communication systems for mobile terminals

Based on experimental data, we have reported a method to scale the cumulative time, TF,T(A), a given attenuation, A (dB), is exceeded in a MEO satellite system in fixed terminals, to the time, TM,T(A), A is exceeded in mobile terminals. Zigzag routes and ring roads simulated city patterns; straight routes simulated freeways. In all cases, TM,T(A) can be expressed as TM,T(A)=ξTF,T(A) with a probability scaling factor ξ independent of A. Although the satellite systems have been simulated at 19.77 GHz, the results concerning ξ can be considered frequency-independent. We have used a very large number of rain-rate maps of storms randomly observed in 1991–1992 by a meteorological radar in Northern Italy. The speed of vehicles was modelled as a lognormal random variable. We found: (a) in zigzag routes TM,T(A)F,T(A), i.e. ξ<1, with results depending on vehicle speed modelling and starting conditions; (b) in ring roads there is no difference between fixed and mobile systems (ξ≈1); (c) in straight freeways TM,T(A)≪TF,T(A) (ξ≪1) and TM,T(A) can change significantly in different straight lines and in opposite directions (anisotropy and asymmetry) for medium–large attenuation. When compared with zigzag routes or ring roads, the performance in straight freeways is the most optimistic. The numerical values of ξ applicable to a MEO satellite system are not significantly different from those applicable to a GEO satellite system working in the same conditions. Copyright © 2002 John Wiley & Sons, Ltd.