Statistical Behavior of Rain Attenuation

The statistics of rain attenuation are important for the design of both terrestrial and earth-satellite radio links using frequencies above 10 GHz. Many experiments 1-33 have been performed to obtain data on rain attenuation for different frequencies, path lengths, and geographical locations. This paper presents the behavior of rain attenuation statistics found in our study to be common to the available experimental data. f Let V{t) be the time-varying amplitude of the received signal voltage normalized to its nonfaded level, * An excerpt of this paper has been presented at the 1972 I E E E International Conference on Communications at Philadelphia, and included in the Proceedings of the Conference. * These data are actual measured microwave rain attenuations and not the approximate attenuations calculated from rain rate data. 557 558 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , A P R I L 1973 = -- 20 logio V(t) be the time-varying rain attenuation in dB, be the expected fraction of time t h a t a(t) exceeds any P(a ^ A) specified value A, Po be the expected fraction of time t h a t rain falls at the location of the radio link, Pcia ^ A) be the expected fraction of raining time t h a t a exceeds A, Oim be the median value of a during the raining time, i.e., Pc{a ^ am) = 0.5, be the duration of rain attenuation fades with a exr{A) ceeding any specified threshold A in dB, be the probability that the fade duration r(A) exPLr(A) ^ bj ceeds any specified duration b, and f ( A ) be the average duration.