Page 211 - Integrated Wireless Propagation Models

I
M i c r o c e I P r e d i c t i o n M o d e I s 189

and the received signal P, is expressed as a function of L'i<j>, shown in Eq. (1.9.1.3.2), as

2
P, = P 0 (47td/A/ (1- cosL'i<)

From the above equation, we can find that when L'i<j> = rc, the received signal P, becomes
maximum:

2
P , = P o 2 (1-cosL'i<) = max when L'i<j> = rc (4.2.1.1.2)
(4rcd/A)
Let L'1< = rc in Eq. (1.9.1.3.6):

2rc 2h,h
rt- _ z _
A - (4.2.1.1.3)
L.l'l' - A d TC
From Eq. (4.2.1.1.3), we can find the near-in distance dr
4hl h
d - 2 (4.2.1.1.4)
J - A
A
where h = height of base station antenna, h = height of mobile antenna, and = wave­
1
2
2
length in meters. The near-in distance was calculated and described in Lee's book. The
criterion for defining the near-in distance is when the phase difference between the
direct wave and the reflected wave is 180°, as shown in Fig. 4.2 1 . 1 . 1 .
.
i
i
Within the near-in distance, the received signal s still very strong and s not dis­
turbed by the reflected wave. We may consider the signal path loss following the free
space path loss in this regain. The near-in distance is used for the microcell model and
can be used for the macrocell model but does not apply for the in-building model. This
is because the angle of incidence of the reflected wave in the in-building environment is
not small. The derivation of the distance in which the received signal is still strong for
the in-building model will be shown in Chap. 5. We call it the close-in distance to distin­
guish it from the near-in distance.

Base
station

Reflection
FIGURE 4.2.1.1.1 The criterion of near-in distance.