Page 297 - Integrated Wireless Propagation Models

I n - B u i l d i n g ( P i c o c e l l ) P r e d i c t i o n M o d e l s 275

signal strength can be calculated based on the propagation characteristics in different
locations. The conditions that need to be checked include humidity and, LOS, it is the
number of rooms blocking the signal, and the distance the receiver is from the transmit­
ter. All this information is stored in the AutoCAD file format. This information makes
the model more capable of handling the positioning of different antennas and easier to
optimize the design. Also, this set of slopes is used for prediction in the model. Every
predicted point is calculated individually based on the multiple-distance component
model to get the signal path-loss value because of its unique position in the building.
The slope in each equation is derived by averaging the loss value from all measured
points. Different sets of slopes will be derived based on the type of rooms (regular
rooms and special rooms).
This empirical slope is used by the Lee in-building (Picocell) model and the Lee
method.3 This is because each building is built differently. But the structure of the gen­
eral formula used in the model is the same. The prediction is made easier by inserting
the empirical slopes. This is the same approach that was used in both the macrocell
prediction and the microcell prediction.

5.2.4 Applications of the Lee Model
The model provides two convenient and easy means for designing in-building systems.
First, buildings are classified into different categories based on the construction materi­
als. These building loss curves derived from the measurements in different buildings
can be put into different look-up tables. As more and more measurement data are col­
lected, the tables will cover more building loss curves and can be applied to predict the
losses from different buildings accordingly. Second, once the building loss curve is
identified based on the building type, the model can be used to design an in-building
system by placing the transmitter at different locations and at different heights and
with different antennas and different ERPs to ensure that the optimized coverage is
achieved with minimum interference.

5.2.5 Characteristics of the Measured Data
Two sets of measured data were collected in two different office buildings. As more
measured data are collected, the model will be fine-tuned. The first set of building char­
acteristics was studied by covering an area from three different transmitter locations
(nodes 1, 2, and 3) in the Qualcomm building, as shown in Fig. 5.2.5.1. Some special
cases were examined from this set of tests in the building, such as the different signal
attenuations that from the elevators. The path loss from LOS and non-LOS conditions
crossing a single room and multiple rooms are also considered.
The second set of building characteristics was collected from the fifth floor of the
AirTouch building located in Walnut Creek, California, shown in Fig. 5.2.5.2.
The size of the building is shown in the figure. All walls are made of business build­
ing material with standard sheetrock and metal studs. In Fig. 5.2.5.2, the clear circles are
three transmitter locations: 1, 2, and 3. The shaded circles marked "1" are the receiver
spots. The solid dark squares and circles are building beams. Each time, only a transmit­
ter was used, and the measurements were taken the same way as in the Qualcomm
building. The position of the transmitter and the routes of measurements taken are
shown in the figures. The comparison of the measured data with the predicted results
will be shown later.