User's Manual

Estimating RF Coverage
6-20 InterReach Fusion Wideband Installation, Operation, and Reference Manual
CONFIDENTIAL D-620616-0-20 Rev B
• Walls are sheetrock construction, suspended ceiling tiles.
• Antennas used are omni-directional, ceiling mounted.
• Standard office environment, 80% hard wall offices and 20% cubicles.
4. Link Budget: In this example, a design goal of –85 dBm is used. Suppose 3 dBi
omni-directional antennas are used in the design. Then, the maximum RF propa-
gation loss should be no more than 94.5 dB (6.5 dBm + 3 dBi + 85 dBm) over
95% of the area being covered. It is important to note that a design goal such as
–85 dBm is usually derived taking into account multipath fading and log-normal
shadowing characteristics. Thus, this design goal will only be met “on average”
over 95% of the area being covered. At any given point, a fade may bring the sig-
nal level underneath the design goal.
Note that this method of calculating a link budget is only for the downlink path.
For information to calculate link budgets for both the downlink and uplink paths,
refer to Section 6.6 on page 6-22.
5. Path Loss Slope: For a rough estimate, Table 6-12, “Estimated Path Loss Slope for
Different In-Building Environments” on page 6-15, shows that a building with 80%
hard wall offices and 20% cubicles, at 1920 MHz, has an approximate path loss
slope (PLS) of 38.1. Given the RF link budget of 94.5 dB, the distance of coverage
from each RAU will be 30.2 meters (99 ft). This corresponds to a coverage area
of 2,868 sq. meters (30,854 sq. ft.) per RAU (refer to Section 6.5.1 for details on
path loss estimation). For this case we assumed a circular radiation pattern, though
the actual area covered depends upon the pattern of the antenna and the obstructions
in the facility.