Page 192 - Integrated Wireless Propagation Models

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

transmitting antenna mast. The height from the intercept point on the transmitting
antenna mast to the antenna top is the effective antenna height.
The calculation of the effective antenna gain is restrained by the noncontinuous ter­
rain data. Every grid along the terrain radial might result in a different effective antenna
gain due to this kind terrain data. Sometimes the effective antenna gain becomes huge
regardless of the elevation of the mobile and the position of the reflection point from the
base station transmitter.
The new algorithm introduced earlier calculates the effective antenna gain based on
all the reflection points and selects the one with the biggest gain.
3.3.2.2 Integrated Solution: Single Knife Edge
This section discusses how the Lee model deals with the natural situation. The shadow
loss and effective antenna gain were calculated separately and applied to calculate the
received signal strength.
If the mobile is at the LOS condition, the received signal strength is
r
P , = P o - y log'o+G ,ffl, (3.3.2.2.1)
If the mobile is behind a single knife edge, the received signal strength is (see Eq. (3.1.2.5))
r
P, = P0 y l og'o+ Max G - L0 (3.3.2.2.2)
-
effl,
where Max G ,1fl is the maximum gain assuming the mobile is on top of a hilU
Figure 3.3.2.2.1 shows using the algorithm on identifying the valid knife edges and
calculating effective antenna gains.

3.3.2.3 Integrated Solution: Multiple-Knife Edge
In this section, the integration of the diffraction loss with the effective antenna height
gain when the mobile is blocked by multiple knife edges is discussed.
Figure 3.3.2.3.1 shows the algorithm on how to identify the valid knife edges and
how to integrate these with effective antenna gains.
Under a multiple-knife-edge condition, the major contributions were the following:

1. Path loss
2. Diffraction loss due to all knives (e.g., sum of the losses from all true knives).
3. Effective antenna height gain from the first knife edge and the h,lh gains from
PP
the rest of the knife edges.
Figure 3.3.2.3.1 explains how to integrate the effective antenna gain in the knife­
edge calculation, especially in the multiple-knife-edge scenarios. h,lh is the effective
PP
antenna height gain while the mobile is blocked. The formulas for knife-edge losses
were discussed in previous sections.

3.3.3 Measured versus Predicted Data
All the field points are collected and used to calculate the path losses along the radial
paths from many cell sites, where the LOS and blocked situations are identified. Those
field points are stored in the drive test database.
Figure 3.3.3.1 shows all measured LOS data compared with the theoretical prediction
curve, the best-fit curve, and the curve generated from the new algorithm. As shown, the