Page 65 - Integrated Wireless Propagation Models

I n t r o d u c t i o n t o M o d e l i n g M o b i l e S i g n a l s i n W i r e l e s s C o m m u n i c a t i o n s 43

1.10.1.3 Point-to-Point Model
This kind of prediction model can predict the received signal strength transmitted from
a given base station and received by a mobile at a given point. This model is considered
to have more practical use. All point-to-point models can be used as area-to-area
models but not vice versa.

1 . 10.2 Prediction Models for Propagating i n Areas of Different Sizes

1.10. . 1 Macrocell Model
2
The macrocell prediction model is used mainly to predict the coverage of a large cell
with maximum power from a base station under government regulation. The interfer­
ence from the co-channel reused cells can be calculated. The predicted carrier-to
interference ratio CII is used to deploy a system. Macrocell prediction models are the
prediction models that were deployed in early cellular systems. When planning a
cellular system in a large area, it is very costly to select proper locations for base stations
based on the measured data in that area. If a wrong location is selected for a base sta­
tion, not only does the system result in a poor coverage but strong interference among
base stations prevails as well. Therefore, this macrocell prediction model is the most
valuable tool among all the other small area prediction models.

1.10.2.2 Microcell Model
The microcell prediction model is used for managing system capacity. The size of the
cells is smaller, and the transmitted power is lower in a confined area. More interference
problems occur, and more handoffs need to be considered. The prediction tool can be
used to optimize the overlaid area between any two adjacent cells for maximizing
system capacity. It is a useful tool for designing a microcell system economically on the
basis of capacity.
(
1.10.2.3 In-Building Model F or Picocell and Femtocell )
Because more people use mobile units (cell phones) while walking inside buildings, a
different prediction model has to be built to deal with this different environment. The
in-building model is especially important with wireless data usages growing exponen­
tially enabled by WLAN /WiFi. To optimize the system with best coverage and mini­
mize interference in very packed rooms/buildings such as picocell becomes more and
more critical. Femtocell is a low power cellular base station, which is targeted for in
home use and small business. The in-building propagation model can be applied to
both picocell and femtocell deployment.

1 . 10.3 Aspects for Predicting the Signal Strengths n a General Environment
i
1.10. . 1 Mobile Path, Radio Path, and Radial Path
3
Local means are calculated from the measured data while the mobile units are traveling
along a road or along a certain path. This path is called the mobile path, as shown in
1
Fig. . 10.3 1 . 1 on the x-axis.
.
However, each local mean is based on a radio path x' between the base station and
the mobile unit at a corresponding spot on the mobile path. Identifying radio paths is
not important if we are modeling an area-to-area model. However, it is very important
for modeling a point-to-point model because from the radio path, the predicted signal
strength at the corresponding location of the mobile unit can be calculated.