Page 155 - Integrated Wireless Propagation Models

M a c r o c e l l P r e d i c t i o n M o d e l s - P a r t 2 : P o i n t - t o - P o i n t M o d e l s 133

.
This is because the value of sin ((�<1>1 - �<1> ) / 2) is very small. From Eq. (3 1 . 6.1.5), the loss
2
factor L, becomes one. It means no loss. Therefore, Eq. (3 1 . 6.1.1) becomes
.
P, = P (1/ ( 4 rtd/').)2 (3 1 . 6.1.6)
.
0
It is a free space path loss. We may conclude that the free space path loss will be observed
when propagation over the water occurs.
For treating the water enhancement, there are two options for determining where
water is located, as follows:
1. Attribute-When the morphology is used as the basis for determining the
location of water.
2. Terrain-If the elevation for any point along the terrain radial path is within
0.2 m of the specified elevation for the water base, then the point is considered
to be located on water for implementing the water enhancement.
Determining the water location from the morphology of water is a more accurate
method. Generally, terrain elevation should be used for this condition only when the
morphology files of water files are not available.

3 . 1 . 6 .2 The Unique Challenges
The location of water presents a unique challenge for radio wave propagation. With
inexpensive and easier access to the morphology and terrain data, it is imperative for a
prediction model to effectively adapt and manage unique water scenarios. The poten­
tial impact on the system performance and resources would be drastic when propaga­
tion over the water occurs.
The objective of this section is to specifically address the enhancement added to the
Lee macrocell and microcell prediction models in order to handle the unique impact on
radio propagation as a result of water surface. It is generally accepted that water enhances
radio signals. However, there are many different impacts at varying levels, depending on
where a mobile is located relative to the positions of water and the base station. An algo­
rithm has been developed to deal with various scenarios in which water plays a critical
role in predicting the effect of propagation loss. With water enhancement, the model can
better predict the radio propagation, which has directly impacted cellular system engi­
neering, most notably in coverage, handoffs, interferences, and thus capacity.
This issue focuses on when and in which cases the water enhancement is imple­
mented. A high-level flow diagram and an individual case-by-case analysis is shown in
this section. It is assumed that the propagation characteristics of uplink are identical to
that of the downlink; therefore, only the characteristics of downlink are illustrated.
There are two generalized cases for the prediction in the proximity of water: case 1, the
mobile receiver has a LOS condition, and case 2, the mobile is blocked from the transmitter
of the base station. ill each case, a number of possible situations can occur in which the water
surface enhances the radio waves. When the "basic model" is referred to, only the regular
prediction algorithms are used; therefore, the water enhancement is not implemented.

3 . 1 .6.3 The Algorithm Diagram
The Lee macrocell prediction model has treated the radio wave as a theoretical ray path.
The reflection point of that ray is obtained by finding a mirror image point of the mobile
antenna in the image plane below either the land level or the water level, depending on