Cisco Unified Wireless IP Phone 7925G Series Deployment Guide
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Multipath
Multipath occurs when RF signals take multiple paths from a source to a destination.
A part of the signal goes to the destination while another part bounces off an obstruction, then goes on to the destination. As a
result, part of the signal encounters delay and travels a longer path to the destination which creates signal energy loss.
When the different waveforms combine, they cause distortion and effect the decoding capability of the receiver as the signal
quality is poor.
Multipath can exist in environments where there are reflective surfaces (i.e. metal, glass, etc.). Avoid mounting access points
on these surfaces.
Below is a list of multipath effects:
Data Corruption
Occurs when multipath is so severe that the receiver is unable to detect the transmitted information.
Signal Nulling
Occurs when the reflected waves arrive exactly out of phase with the main signal and cancel the main signal completely.
Increased Signal Amplitude
Occurs when the reflected waves arrive in phase with the main signal and add on to the main signal thereby increasing the
signal strength.
Decreased Signal Amplitude
Occurs when the reflected waves arrive out of phase to some extent with the main signal thereby reducing the signal
amplitude.
Use of
Orthogonal Frequency Division Multiplexing (OFDM)
, which is used by 802.11a and 802.11g, can help to reduce issues
seen in high multipath environments.
100
mW
50 mW
