User's Manual

Designing a Unison Solution PRELIMINARY
8-20 InterReach Unison User Guide and Reference Manual
PN 8700-10
620003-0
8.2.1 Path Loss Equation
Indoor path loss obeys the distance power law
1
in equation (2):
PL = 20log(4πd
0
f/c) + 10nlog(d/d
0
) + Χ
s
(2)
where:
• PL is the path loss at a distance, d, from the antenna (the distance between the
antenna that is connected to the RAU and the point where the RF signal
decreases to the minimum acceptable level at the wireless device).
•d
0
is usually taken as 1 meter of free-space.
• f is the operating frequency in hertz.
• c is the speed of light in a vacuum (3.0 × 10
8
m/sec).
• n is the path loss exponent and depends on the building “clutter”.
•
Χ
s
is a normal random variable that depends on partition losses inside the build-
ing, and therefore, depends on the frequency of operation.
As a reference, the following table gives estimates of signal loss for some RF barriers.
1
1. Rappaport, Theodore S. Wireless Communications, Principles, and Practice. Prentice Hall PTR, 1996.
Table 8-16 Average Signal Loss of Common Building Materials
Partition Type
Loss (dB)
@ <2 GHz Frequency (MHz)
Metal wall 26 815
Aluminum siding 20 815
Foil insulation 4 815
Cubicle walls 1.4 900
Concrete block wall 13 1300
Concrete floor 10 1300
Sheetrock 1 to 2 1300
Light machinery 3 1300
General machinery 7 1300
Heavy machinery 11 1300
Equipment racks 7 1300
Assembly line 6 1300
Ceiling duct 5 1300
Metal stairs 5 1300