Watchguard Firebox SOHO 6 Wireless User Manual page 37

path-loss than signals with a higher wavelength in the
same frequency range.
In a typical office environment, the calculated loss is only
accurate for approximately 20 feet. For each additional
100 feet, an additional 30 dB must be added. The additional
interference is caused by furniture, walls, windows, and
other objects in the area.
Another cause of signal attenuation is "fading due to
multi-path reflections." Multi-path reflections are the result
of an RF signal traveling along more than one route from
the transmitter to the receiver. Multi-path occurs when a
signal is reflected by surfaces in the environment. A signal
with a frequency of 2.4 GHz will be reflected by many
surfaces. When multi-path occurs, some combinations of
reflected signals will cancel each other out.
The signal attenuation caused by multi-path reflections is
highly dependent on antenna position. When the receiver
is moved at least ½ wavelength, the signal strength can
vary by as much as 30 dB. To compensate for this problem,
the SOHO 6 Wireless uses "antenna receiver diversity." In
this system, the effect of multi-path fading is reduced
through the use of two antennas that are spaced more than
½ wavelength apart. The SOHO 6 Wireless automatically
selects the antenna that receives the stronger signal.
Laptop computers typically have one antenna, which is more susceptible
to signal fading caused by position. For this reason, the SOHO 6 Wireless
may receive signals from the laptop while the laptop does not receive
signals from the SOHO 6 Wireless.
User Guide
Understanding IEEE 802.11b Wireless Communication
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11