Page 113 - Integrated Wireless Propagation Models

M a c r o c e l l P r e d i c t i o n M o d e l s - P a r t 1 : A r e a - t o - A r e a M o d e l s 91

The field strength at each measurement point is calculated for a given percentage of
time inside the range from 1 to 50 percent. The field strength will be exceeded for t% of
times at each receiver location given by

E(t) = E, (median) + Qi(t / 1 0 0) cr dB(j..tV /m) (2.17.1.1)
T
where E, (median) is the median field strength with respect to the time at the
receiver location, Qi(x) is the inverse complementary cumulative normal distribu­
tion as a function of probability, and cr is the standard deviation of normal
T
distribution of the field strength at the receiver location. ITU-R P1546 is intended to
provide the statistics of reception conditions over a given area, not at any particular
point. The field strength value at q% of location within an area represented by a
square of 200 x 200 m is given by

E(q) = E (median) + Qi(q/ 1 0 0) crL dB(j..tV /m) (2.17.1.2)
L
where E (median) and cr L are the median and standard deviation of field strength over the
L
defined area, respectively and q is the percentage of location varying between 1 and 99.
When the terrain information is available, the transmitting (base) antenna height h1
should be obtained as follows:

Condition 1: For land paths shorter than 15 km,

where hb is the height of the antenna above terrain height averaged between 0.2 d and d
in kilometers and d is the distance between the transmitter and the receiver.
Condition 2 : For land paths of 15 km or longer,

h = h,ff
i
where heff is defined as the transmitter height in meters over the average level of the
ground between distances of 3 and 15 km from the transmitting (base) antenna in the
direction of the receiving (mobile) antenna.
The following formulas are used according to the recommendation for field strength
prediction:
.
ld = log10 (d) (2.17 1 .3)
log10 (�)
k = (2.17.1.4)
log10 2
2
.
E1 = (a0F + a 1k + a 2)ld +(0.1995k + 1 . 8671K + a 3 ) (2.17 1 .5)
1d b2
E,e fl = b 0[exp(-b4 1 0 1; ' ) - 1 ] + b 1 · exp[-( � J J (2.17 1 .6)
.
(2.17 1 .7)
.
(2.17.1.8)