Call Capacity - Cisco 7925G Deployment Manual

When 802.11b clients exist in the wireless network, then an 802.11b rate must be enabled and only an 802.11b rate can be
configured as a mandatory / basic rate.
The recommended data rate configurations are the following:
802.11 Mode
802.11a
802.11b
802.11b/g
For a voice only application, data rates higher than 24 Mbps (36, 48 and 54 Mbps) can optionally be enabled or disabled, but
there is no advantage from a capacity or throughput perspective and enabling these rates could potentially increase the number
of retries for a data frame.
If deploying in an environment where excessive retries may be a concern, then a limited set of the data rates can be used (e.g.
12, 24, 54), where the lowest enabled rate is the mandatory / basic rate.
For rugged environments or deployments requiring maximum range, it is recommended to enable 6 Mbps as a mandatory /
basic rate.
To preserve high capacity and throughput, data rates of 24 Mbps and higher only can be enabled (24-54 Mbps).
Other applications such as video may be able to benefit from having these higher data rates enabled.
Note: Some environments may require that a lower data rate be enabled due to use of legacy clients, environmental factors or
maximum range is required.
Set only the lowest data rate enabled as the single mandatory / basic rate. Multicast packets will be sent at the highest
mandatory / basic data rate enabled.
Note that capacity and throughput are reduced when lower rates are enabled.
If Call Admission Control (TSPEC) is enabled then the Traffic Stream Rate Set (TSRS) feature will also be enabled, which can
allow lower rates to be enabled for legacy devices, while preventing the Cisco Unified Wireless IP Phone 7925G, 7925G-EX,
and 7926G from transmitting at rates below 12 Mbps for 802.11a and 11 Mbps for 802.11b/g as well as not above 24 Mbps if
the Restricted Data Rates feature in Cisco Unified Communications Manager is enabled. Disallowing packets to be transmitted
at lower rates preserves capacity. Sending voice frames at a more reliable rate (i.e. 24 Mbps) initially can potentially reduce the
number of retries of a frame to ensure the packet transmission is successful on the first try.
See the Product Specific Configuration Options
the Cisco Unified Wireless IP Phone 7925G, 7925G-EX, and 7926G in order to utilize the TSRS feature.

Call Capacity

Design the network to accommodate the desired call capacity.
The Cisco Access Point can support up to 27 bi-directional voice streams for both 802.11a and 802.11g at a data rate of 24
Mbps or higher. To achieve this capacity, there must be minimal wireless LAN background traffic and radio frequency (RF)
utilization.
The number of calls may vary depending on the data rate, initial channel utilization, and the environment.
Max # of Streams
13
Cisco Unified Wireless IP Phone 7925G, 7925G-EX, and 7926G Deployment Guide
Mandatory (Basic)
Data Rates
12 Mbps
11 Mbps
11 Mbps
section for information on how to configure the Restrict Data Rates options on
802.11 Mode
802.11a or 802.11g + Bluetooth Disabled
Supported (Optional)
Data Rates
18-24, <36-54> Mbps
None
12-24, <36-54> Mbps
Disabled
Data Rates
6, 9, <36-54> Mbps
1, 2, 5.5 Mbps
1, 2, 5.5, 6, 9, <36-54> Mbps
Data Rate
6 Mbps
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