Land-mobile satellite excess path loss measurements

This paper describes an experiment conducted with the ATS-6 satellite to determine the additional path loss over free-space loss experienced by land-mobile communication links. This excess path loss is measured as a function of (1) local environment, (2) vehicle heading, (3) link frequency, (4) satellite elevation angle, and (5) street side. An excess loss model developed from the data shows that the first two parameters dominate. Excess path loss on the order of 25 dB is typical in urban situations (90% temporal/spatial coverage), but decreases to under 10 dB in suburban/rural areas. Spaced antenna selection diversity is found to provide only a slight decrease (4 dB typically) in the urban excess path loss observed. Level crossing rates are depressed in satellite links relative to those of Rayleighfaded terrestrial links, but increases in average fade durations tend to offset that advantage. The measurements show that the excess path loss difference between 860 MHz links and 1550 MHz links is generally negligible.