Video Calls; Dynamic Transmit Power Control (Dtpc); Multipath - Cisco 9971 Deployment Manual

Video Calls

Video calls over Wireless LAN will significantly reduce the potential call capacity.
Below are the maximum number of video calls supported per access point / channel for each recommended video rate.
Max # of Video Calls
4-10
3-7
2-5
Note: Currently no Call Admission Control support for video.

Dynamic Transmit Power Control (DTPC)

To successfully exchange packets between the wireless IP phone and the access point, Dynamic Transmit Power Control
(DTPC) should be enabled.
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 as that will not advertise DTPC to the client.
If the access point does not support DTPC, then the Cisco Unified IP Phone 9971 will use the highest available transmit power
depending on the current 802.11 mode and data rate. This setting prevents one-way audio when RF traffic is heard in one
direction only. By default the Cisco Unified IP Phone 9971 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 IP Phone 9971
can support.

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.
Cisco Unified IP Phone 9971 Wireless LAN Deployment Guide
802.11 Mode
802.11a or 802.11g + Bluetooth
Disabled
802.11a or 802.11g + Bluetooth
Disabled
802.11a or 802.11g + Bluetooth
Disabled
Video Rate 802.11 Data Rate
384 Kbps 12-54 Mbps
512 Kbps 12-54 Mbps
1 Mbps 12-54 Mbps
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