Page 122 - Integrated Wireless Propagation Models

100 C h a p t e r T h r e e

Based on the measurement results, the Lee model is enhanced to combine line-of­
sight (LOS) gain and non-line-of-sight (NLOS) loss together for more realistically pre­
dicting the signal strength. This is covered in Sec. 3.3 of enhanced Lee model.
This chapter focuses on theoretical and technical aspects of the algorithm of Lee
macrocell modeling.

M
o
3 . 1 . 1 I m p lementation f the Lee a crocell Model
3 . 1 . 1 . 1 Models of Implementation
Three modes of the Lee macrocell model are analyzed here. The basic mode of the
Lee model is the Lee single breakpoint model; the other two modes are the multiple
breakpoint model and the automorphology model.
The other two modes of macrocell model are derived from the Lee single break­
point model. Therefore, the theoretical discussion in this chapter focuses primarily on
the Lee single breakpoint model, with additional explanations of how the other two
modes differ from it.
In implementation, the easiest way to select a mode among the three modes is based
on the granularity in a sector-by-sector basis. Thus, a coverage plot may consist of dif­
ferent sectors using different modes, based on the appropriate modeling objectives for
dealing with different specific propagation conditions in a given sector.
The accuracy of using each mode depends on a number of factors, as discussed
below. Users have the opportunity to customize a certain mode among the three modes
in the Lee macrocell model by feeding the empirical data into the modeling parameters
to increase prediction accuracy and to meet the specific.

3 . 1 . 1.2 Accuracy of Model Variations
The multiple breakpoint model is currently considered to provide the most accurate pre­
diction and is the one recommended to be used. This model was designed specifically to
improve prediction accuracy for "near in" distances (within 1 mile from the base station).
Imported empirical data can be used to increase the accuracy of both the single
breakpoint and the multiple breakpoint models through a technique known as mea­
surement integration. Many radial zones can be identified due to the user's specified
requirements from running this process; the more zones identified, the more accurate
the prediction results provided.
The degree of accuracy of signal strength predictions is based on the automorphol­
ogy model and depends on a careful selection of a path loss slope value for each land­
use class based on an appropriate propagation condition. But measurement integration
technique cannot be used with this mode.
All three modes of the Lee macrocell model may be customized to the extent that
certain model parameters and constants can be specified in a particular mode.
• Model parameters, which include the radial length increment dx (sampling
interval), gain factor, loss factor, and a distance from reflection point and a
mobile signal smoothing. Values for these model parameters may be used for
the choice of modes, path loss, intercept point value, and so on associated with
each different environment type.
• System constants, which include parameters related to the use of water
enhancement, earth curvature, and terrain averaging.