Dynamic Transmit Power Control (Dtpc); Multipath - Cisco 7925G Deployment Manual

Dynamic Transmit Power Control (DTPC)

To successfully exchange packets between the wireless IP phone and the access point, you need to configure Dynamic Transmit
Power Control (DTPC).
When using an access point that supports DTPC, set the client power to match the local access point power.
Do not use default setting of Max power for client power on Cisco autonomous access points as that will not advertise DTPC to
the client.
If the access point does not support DTPC, then the Cisco Unified Wireless IP Phone 7925G will use the highest available
transmit power depending on the current 802.11 mode and data rate.
The transmit power on the Cisco Unified Wireless IP Phone 7925G can also optionally be configured to match the highest
transmit power of an access point in the wireless LAN. This setting prevents one-way audio when RF traffic is heard in one
direction only.
By default the Cisco Unified Wireless IP Phone 7925G will use the highest available transmit power by default (i.e. 17 dBm /
50 mW for 2.4 GHz and 16 dBm / 40 mW for 5 GHz).
The access point's radio transmit power should not have a transmit power greater than what the Cisco Unified Wireless IP
Phone 7925G can support.
100 mW 50 mW

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:
Cisco Unified Wireless IP Phone 7925G Deployment Guide 34