Page 114 - Integrated Wireless Propagation Models

92 C h a p t e r T w o

(2.17.1.9)

.
(2.17 1 . 1 0)
.
(2.17 1 . 1 1)
(2.17.1.12)

E1, = 1 06.9-20/d (2.17.1.13)

(2.17.1.14)

(2.17.1.15)

E, = Eh + corrections dB (11 %) (2.17.1.16)

In the above equations, d and h1 are in kilometers and meters, respectively; E is the
fs
free space field strength; and Eh is the propagating field strength without considering
• , a7,
the corrections. Both E 1s and Eh are received from 1 kW ERP. All coefficients a0, a1, • •
b0, b1, • , b7, c0, c1, . . . , c , d0 are given for nominal frequencies and time percentage in the
•

•
6
recommendation. These coefficients are defined as the optimization parameters in the
optimization algorithm. C R ' ch ' curb n' C TCA ' and ch < 0 are the corrections for effective
a
,
,
E P
radiated power, receiving (mobile) antenna height, short urban/suburban paths, ter­
rain clearance angle, and negative values of h1, respectively. The related formulas for
calculation of c,, ' curb n' C TCA and ch < 0 can be found in.31 The correction C R must
a
i
E P
be added to Eh if fue ERP of the transmitter antenna is not equal to the nominal value of
1 k W:
C ERP = 10 log10 (�:0) (2.17.1.17)
The above formulas are used according to the recommendation P.1546 for point-to-area
field strength prediction.
2 .1 7 .2 Recommendation IT - R P. 5 30-932
U
This ITU terrain model is based on diffraction theory and provides a relatively quick
means of determining a median path loss.32 Diffraction loss will depend on the type of
terrain and the vegetation. For a given path ray clearance, the diffraction loss will vary
from a minimum value for a single-knife-edge obstruction to a maximum for smooth
spherical earth. Methods for calculating diffraction loss for the single-knife-edge case
and for the smooth spherical earth case as well as for paths with irregular terrain are
discussed in Recommendation ITU-R P.526-Knife-Edge Diffraction. These two cases
1
are shown in Fig. 2.17.2. .
b
The diffraction loss over average terrain can e approximated for losses by the formula
(2.17.2.1)