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178 C h a p t e r T h r e e
The diffraction losses L1 and L 2 are then estimated using
(3.4.2.13)
(3.4.2.14)
The diffraction loss L0 at a mobile located at a distance d from the base station is
(3.4.2.15)
where
(3.4.2.16)
and
(3.4.2.17)
o
L = Afo + L - d m d
z
z
where an empirical clutter factor A1o is determined as
(3.4.2.18)
where Afi, is given by
(3.4.2.19)
and o(d ) is given by
L5
o(d ) = 0.78h (d)exp{-O.S[M(d)]+} m (3.4.2.20)
L5
The Langley-Rice model has used the empirical formulas based on the measured
data to predict the path loss. This model has been widely used in US government
projects.
3.5 Summary
This chapter focuses on macrocell modeling. Although two models were discussed, the
key is to understand those approaches that different models take to solve the common
problems. The input from measured data should be carefully examined before use. The
characteristics of the mobile environment and the algorithms from the different models
that deal with these issues are discussed.
The Lee model has been around for a long time. The earlier version of Lee model
has been used by AT&T and named the ADMS planning tool.33 The later version has