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

3-6
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
0.
5
⎪
⎧
0.
5
⎡⎛
1 ⎞ ⎛ 1 ⎞ ⎤⎪
⎫
A(
P,
θ , f ) = A(
P,
θ , f L ) exp⎨1.
5⋅
⎢ ⎜
⎟ − ⎜ ⎟ ⎥⎬
(3-1)
⎪⎩ ⎢⎣
⎝ f L ⎠ ⎝ f ⎠ ⎥⎦
⎪⎭
and for 80% ≥ P > 20% and 20°≤ θ ≤ 60°
⎛ 80 ⎞
ln⎜
⎟
( , , ) ( 20%,
, )
⎝ P
A P θ f = A θ f
⎠
ln( 4)
(3-2)
where A( P, θ , f ) is the attenuation (in dB) at the frequency f (in GHz) exceeded at P (in
%) which represents the percentage of the driving distance for an Earth-satellite path
angle θ (in degrees), and A( P, θ , f L ) is the corresponding attenuation (in dB) at f L =
1.5 GHz. The attenuation is defined relative to non-shadowed and negligible multipath
conditions.
The L-Band attenuation at f L = 1.5 GHz (i.e., A( P, θ , f L ) ) for 20% ≥ P ≥ 1% and
20°≤ θ ≤ 60°
is given by
where
and where
A( P,
θ, fL
) = −M
( θ ) ln( P)
+ N ( θ )
(3-3)
M ( θ ) + cθ
2
= a + bθ
(3-4)
N ( θ ) = dθ
+ e
(3-5)
a =
b =
c =
e =
3.
44
0.
0975
−0.
002
d = −0.
443
34.
76
(3-6)
In Equation (3-3), P is in %, θ is in degrees, f is in GHz, and A( P, θ , f L ) is in dB.
Substituting (3-4) through (3-6) into (3-3), A( P, θ , f L ) may alternately be expressed by
A( P,
θ , fL
)
+ P θ
2
= α(
P)
+ β ( P)
θ γ ( )
(3-7)
where α( P), β( P), γ(
P ) are tabulated in Table 3-1 for a series of fixed percentages in the
interval between 1% and 80%.