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FIGURE 5.2.8.3.1 Mobile outside the room but blocked.

5.2.8.3 Potential Areas for Lee Model Enhancements
To make the model effective, simple formulas are provided by the Lee model to cover
general cases. However, there are some special cases need to be addressed.
Potential issue with the Keenan-Motley model are the following: 12

1 . The LOS loss applied after the breakpoint can be in question. This number can
be potentially huge and is not practical. For example, the 0.2-dB I m attenuation
factor after the breakpoint can potentially run to a 40-dB loss within a 200-m
span. Also, the loss within the LOS category is difficult to justify and apply.
This issue was discussed in the Lee model.
2. The NLOS loss right behind an office in a corridor is not properly addressed. As
shown in the Fig. 5.2.8.3.1, the situation when the mobile is behind the room
(not inside the room) is not properly addressed. For example, in Fig. 5.2.8.3.1,
the mobile at locations 1 and 2 will have the same predicted signal strengths,
while in reality, the signal strength at point 2 will most likely be much higher
because of the deflection of the radio wave. Applying a flat wall loss will not be
general enough to address different locations behind and around a room. This
issue has been better addressed in the Lee model.

5.2.8. . 1 Enhancements of the Lee Model
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The following areas are properly taken care in the enhancement of Lee model in Sec. 5.3:
1. LOS loss is represented by the Lws parameter, in which the RF characteristics
are properly addressed and used after the close-in distance.
2. Loss inside the room is properly addressed with its RF characteristics inside the
room.
3. Aggregate calculation of the model takes care of not only the thickness of wall
but also the number of rooms where the radio wave actually travels.
Beside the areas of concern stated above, there are two additional enhancements.
The layering concept is used to include the quality of service (QoS) requirement and the
characteristics of room/ area. A special area can be identified by marking that area with
a specific value. The model has the intelligence to handle the propagation in these two
areas. These two enhancements can ensure that the deployment of WLAN in picocells