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

3-2
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
In Figure 3-1, fluctuations in the relative power (±1 dB) and in phase (±15°) are due
to both system noise and to a small extent multipath. Nominally, peak-to-peak variations
of less than 5 dB of power and 25° of phase may arise from multipath for non-shadowed
cases. The shadowed case (Figure 3-2) has fades that are highly variable with
fluctuations exceeding 15 dB. Some of these deep fades are also accompanied by rapid
phase shifts. Time-series of fade and phase of the above types were obtained for various
LMSS scenarios and environments and corresponding cumulative distributions were
derived as described in the following paragraphs.
Relative Power (dB)
Phase (deg)
5
0
-5
-10
-15
-20
180
135
90
45
0
-45
-90
-135
-180
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time (s)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time (s)
Figure 3-1: Time-series of 1.5 GHz fade (top) and phase (bottom) over a one second
period at a sampling rate of 1 KHz. Measurements were taken of transmissions from
MARECS-B2 at 22° elevation along an open road near Bismarck, North Dakota.