Page 248 - Integrated Wireless Propagation Models

226 C h a p t e r F o u r

4.3.2 Treatment of Measured Data

4.3.2. 1 Finding the Propagation Path Loss Slopes
When the measurement data exist in the range from d to d a best-fit slope 1 is obtained,
l
1
f
'
including the measured power Pd at the near-in distance d to a distance d Similarly, if
r
f
f
the measured data exist in the range from d to r0 or 1-mile, a best-fit line slope 1 is
1
2
obtained.
A. Area after the first breakpoint
If the measured data exist in the range d to d the received signal P , can be predicted as
1
f
d
P, = Pa -11 log d (4.3.2.1.1)
f
f
where pd = the power at the intercept of the path loss slope ro (= free space path loss
f
slope) and at the near-in distance d in dBm (Eq. [4.3.1.3]) and
f
1 = the best-fit slope from the measurement data in dB I dec.
1
B. Area after the second breakpoint
If the measured data exist in the range from d to r0 (or 1 mile), then the received signal
1
P, can be predicted as
(4.3.2.1.2)
where 1 = the best-fit slope in the range from d to r0, where d < r0 (r0 is usually equiv­
1
1
2
alent to 1 mile);
Ge t = effective height gain; and
f f!
d = near-in distance in meters.
f
The lines 1 of Eq. ( 4.3.2.1.2) and y of Fig. 4.3. . 1a intersect at a point within a range
1
2
from d to r0 (at 1 mile). The received signal at d is Pa · Hence, the received signal
1
1
,
strength in the range from d to 1 mile is obtained.
1
C. Finding the intersection point of two slopes, 1 and y, at distance d by letting
1
1
1 = y in Fig. 4.3.1 . 1, then the distance d can be found as shown below.
1
1
We can eliminate the path loss slope 1 if we can find the intersection point of the
2
slope 1 and the slope y at the distance d • The intersection point at the distance d in
1
1
1
the range d < d < r0 can be obtained by solving Eqs. (4.3.2.1.1) and (4.3.l.la). We get
1
f
the distance d at which the intersection point of slopes 1 and y occurred:
1
1
(4.3.2.1.3)
y
When the slopes 1 and a re known, the distance d can be determined as follows:
1
1
(4.3.2.1.4)