Autonomous APs are useful in small-scale deployments but lack the centralized configuration management needed for a large-scale enterprise WLAN deployment. And they aren't available with built-in site survey tools. If you run a WLAN switched infrastructure, site-survey tools are typically built into the WLAN switches, so before you even purchase an AP you can use those estimation tools to gauge the number of APs you'll need and where to place them.
Aruba Networks, Cisco and other vendors offer integrated site-survey estimation tools in their WLAN switches. These tools vary slightly in their functionality but, generally speaking, work like this: After you scan in your floor plan as an image file (JPEG, GIF or PNG, for instance), the tool prompts you for your per-user bandwidth requirements; whether the WLAN will be 802.11a or 802.11b/g or both; the number of users per access point; whether voice over WLAN is required; and the areas of the floor plan that won't be wireless.
The tools then perform calculations to come up with recommendations, such as optimal placement of APs, RF channel and expected coverage. You can manipulate the results to further customize your WLAN design.
Aruba Mobility Management System Tool
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Aruba's offering is not a standalone product, but rather a "license-free" feature of the management interface for Aruba's Mobility Controller Web-based wireless LAN switch. Cisco offers a application called Wireless Control System that runs on a Windows-based server platform and must be purchased separately (WCS is a popular, $4,000 infrastructure add-on for WLAN management).