Hi David,
Hopefully this info will help;
Number of 802.11b Phones per AP
Before any discussion about network planning can take place, it helps to understand the basics of the overall network capacity.
The following network capacity guidelines apply to sizing the Wireless IP Telephony network:
No more than 7 concurrent G.711 calls per AP.
No more than 8 concurrent G.729 calls per AP.
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Note These design recommendations assume that Voice Activity Detection (VAD) has been disabled on the Cisco 7920 Wireless IP Phones. Use of VAD on the Cisco 7920 phones can conserve bandwidth, but Cisco recommends that you disable VAD on all Cisco CallManager servers to provide better overall voice quality.
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In addition to determining how much bandwidth is needed for an 802.11b VoIP call, you must also consider overall radio contention for a particular RF channel. The general rule is that you should not deploy any more than 20 to 25 802.11b endpoints per AP. The more endpoints you add to an AP, the more you reduce the amount of overall bandwidth and potentially increase transmission delays.
The maximum number of phones per AP depends on the calling patterns of individual users (based on Erlang ratios). Cisco recommends no more than 7 concurrent calls using G.711 or 8 concurrent calls using G.729. Beyond that number of calls, when excessive background data is present, the voice quality of all calls becomes unacceptable.
From this doc;
http://www.cisco.com/en/US/products/hw/phones/ps379/products_implementation_design_guide_chapter09186a00802a0a05.html
Here is another good doc to have a look at;
Is Your WLAN Ready for Voice?
http://www.cisco.com/en/US/netsol/ns340/ns394/ns348/networking_solutions_white_paper0900aecd80472e80.shtml
Hope this helps!
Rob
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