Page 416 - Integrated Wireless Propagation Models

394 C h a p t e r S i x

and link budget analysis in designing a system. This chapter also provides a more
detailed and insight view of the Lee comprehensive models.
Usually, the ray tracing and FDTD techniques are very accurate for finding radia­
tion patterns from exciting an incident wave on an object of a known shape. However,
in a small area with irregular human-made structures, such as buildings, those rays
bouncing and reflecting from the buildings based on ray-tracing techniques or FDTD
cannot come to give accurate predictions of signal strength at the mobile unit, but rather
are statistical in nature. Using both ray-tracing and FDTD techniques is complicated
and costly. Therefore, using empirical data to form a statistical prediction model of path
loss can allow one to predict the receiving signal in a small area fairly well and is simple.
Furthermore, when an area is small, we can install the base stations or access points by
using the cut-and-try method. Sometimes, even though we use either the ray-tracing
techniques or the statistical prediction model, such as Lee in-building model, to first
install the base stations, we still have to use the cut-and-try method to move the base
stations around and fine-tune their locations.
Table 6.8.1 comprises the characteristics of the propagation models with their tech­
niques. The Lee model is compared with theoretical and empirical and statistical pre­
diction models on characteristics, data requirements, ease of integration, and speed of
calculation with high accuracy.
Form Table 6.8.1, the advantage of using the Lee comprehensive model is that it is a
compound of all three model types-theoretical, empirical, and statistical. Also, it inte­
grates three cell size-specific models-macrocell, microcell, and picocell (in-building).
The software tool is easy to use in designing a large system with relatively less effort.
In Sec. 6.7, we have explored four different media. Each of them is unique and
different from the terrestrial mobile medium. The property of each medium and the

Suitable Experimental Details of
Model Name Environment Complexity Data Environment Accuracy Time Other
Theoretical Macro, micro, H i gh N/A Low-high Good Can Not integrated
and pico (depends on be with limited
accu racy) long accu racy

Empirical Macro, micro, Medium Yes Medium Good Short Not integrated
and pico Can fi ne
tune with
measurement
data
Statistical Macro, micro, Low Yes Low Good Short Not integrated
and pico
Lee( compound Macro, micro, Low Yes Low Good to Short Fu lly
of theoretica l , a n d pico great integrated
statistic l , Can fi ne
a
empirical) tune with
measurement
data
TABLE 6.8.1 A Comparison of Various Models