Page 92 - Integrated Wireless Propagation Models

70 C h a p t e r T w o

where 4 = total loss (dB); Lr = free space loss (dB);
F8 = propagation factor (dB); L0 = diffraction loss (dB);
Y = correction factor (dB); fc f requency (HHz);
=
R = distance between antenna (km); hb, h"' = base and mobile station effective
antenna heights (m);
A. = wavelength (m); d = distance between antenna (m)
= 1000 R;
=
d e arth radius (6.371 X 106m);
K = earth radius factor (�for standard ratio atmosphere); and
cb, c"' = dielectric constant at the base and mobile stations (normally taken as 10 over
dry terrain).

2.11 l b r a h i m - P a r sons ModeP 7 ·18

2 . 1 1 . 1 Findings from the Empirical Data
This empirical model is applied to urban environments. It was based on the field trials
in London between an elevated base station and a mobile moving in the city streets at
frequencies of 168, 445, and 896 MHz. Measured data were collected with base station
1
antennas at a height of 46 m above local ground. 6 Samples were taken every 2.8 em.
List of principal symbols:
H = relative mobile spot height, m
L1 = free space propagation loss, dB
Lr = plane earth propagation loss, dB
L0 = terrain diffraction loss, dB
L = land usage factor
U = degree of urbanization factor
=
PL p redicted median path loss between two isotropic antennas, dB
d = range, m (d :::; 10,000 m)
f = transmission frequency, MHz
h, = transmitter antenna height above local ground level, m
h, = receiver antenna height above local ground level, m (h, :::; 3 m)
The data were collected in batches, each batch representing a square of 0.5 km coin­
ciding with the National Grid System. This size of test square was judged suitable so
that the propagation data become representative in the urban environment. The layout
1
of the test squares in London is shown in Fig. 2.1 . 1 . 1 . The average route length within
1
each test square was . 8 km.
Each square is assigned three parameters, H, U, and L, defined as follows:
H (terrain height) is defined as the actual height of a peak, basin, plateau, or valley
found in each square or the arithmetic mean of the minimum and maximum heights
found in the square if it does not contain any such features.
U (the degree of urbanization factor) is defined as the percentage of building site area
within the square that is occupied by buildings having four or more floors. U varied