Crash Course: Wireless Site Surveys
Cornell W. Robinson III
May 31, 2006
Neither tool is comprehensive, however, when it comes to predicting propagation through physical obstacles and WLAN coverage. Aruba's tool doesn't take into account propagation through a variety of building materials, but Cisco's tool lets you assign to up to seven categories of wall types, so it's a little more helpful. Both the Aruba and Cisco tools generate suggested AP placement, RF channel assignment, RF power settings and expected data rates, all of which are depicted with heat maps on the floor plan (see screen, left).
The visualization feature in these tools is customizable, so you can virtually add APs or move around APs generated by the tool, for example. But beware that these tools are vendor-specific--Aruba's tool can only be used with an Aruba WLAN--and their estimations are not precise.
Most APs continuously scan their WLAN environments, conducting 24x7 site surveys and providing things such as automatic channel assignment, dynamic power adjustment, collision avoidance through automated stand-by operation and the ability to feed data to real-time visualization tools. The visualizations are updated and supported by actual readings gathered by the APs, and offer real-time site surveys of your WLAN RF environment. The APs, meanwhile, continuously adjust themselves to avoid channel overlap and problems in the wake of adds, moves and changes.
Laptops and Walk-Throughs
A manual site survey makes sense if your site is too small to justify an expensive enterprise WLAN switch architecture and instead will have autonomous APs, or if your WLAN environment is too specialized--think warehouses, hangars, ships and outdoor WLANs--for the cookie-cutter estimation tools. But you can put away your markers and floor plans because there are some helpful tools priced around $3,000 for manual site surveys, too.