Handbook of Propagation Effects for Vehicular and ... - Courses

Optical Methods for Assessing Fade Margins 10-11
Probability (%) Fade > Abscissa
99
98
95
90
80
70
60
50
40
30
20
10
5
2
1
London
Singapore
Cumulative Fade Distribution
For the Globalstar Constellation
Using the Highest Satellite
Tokyo
-5 0 5 10 15 20 25 30 35
Fade (dB)
Figure 10-6: Cumulative fade distribution for Globalstar satellite constellation associated
with “highest” satellite diversity scenario. The path state vector components for London,
Tokyo, and Singapore are given in Table 10-5.
10.7 Statistics of Potentially Visible Satellites in Various States
In order to establish a priori an optimum communications strategy for any given landmobile
satellite system, it is desirable to have knowledge of the statistics associated with
the “states” of the “potentially visible” satellites. In this section, we describe such a
statistic assuming the Globalstar system of satellites at the geographic locations of
Tokyo, London, and Singapore. As mentioned, “potentially visible” is defined as a
satellite at an elevation angle above 10°.
Figure 10-7 through Figure 10-9 are three-dimensional bar charts describing
satellite constellation and path-state mixture statistics for Tokyo, London, and Singapore,
respectively. The vertical scale signifies the joint probability (in percent) that the
indicated numbers of satellites are potentially visible with the shown state mixture. The
scale labeled “Mixed State” represents the various combinations of states for up to four
potentially visible satellites. For example, CCSB corresponds to the states clear, clear,
shadowed, and blocked for four potentially visible satellites. When three satellites are
potentially visible, we take the first three states; namely, clear, clear, and shadowed. For
the two-satellite case, this nomenclature implies the clear, clear state, and for one
satellite, it represents the clear state. The indicated “All” state denotes all the satellites