RollOut: Ekahau's Site Survey 2.2

Good wireless networks don't just happen. Proper access point placement and knowledge of the spaces to be covered are critical, and freebie tools are rarely good enough for enterprise planning. In contrast, Ekahau's Site Survey 2.2 provides an effective suite of surveying and planning tools that demystifies the deployment and support of Wi-Fi networks.

The latest Site Survey scales better than previous versions, supporting significantly larger planning maps with AP plotting and simulated displays that are much faster on the draw. The same map with dozens of APs opens several seconds faster for 2.2 than it did in earlier versions. The product now supports several new wireless adapters, reflecting the ever-growing crop of cards available. And special attention has been given to optimizing scan speeds in the many eligible Atheros-based NICs likely to be used with the product.Contemporary survey tools, such as AirMagnet Surveyor and the old free standby NetStumbler, may stand alone; others, such as Location Manager in Cisco's Wireless LAN Solution Engine (WLSE), are packaged into management systems. Site Survey is autonomous. To keep the NIC and driver prerequisites simple, Ekahau uses a wide range of off-the-shelf wireless card and driver combinations to gather data and make accurate predictions. Some tools, including Surveyor, require a proprietary driver and tie their tool to a single NIC for licensing purposes.

Past, Present and Future

Common survey-related tasks include planning wireless networks for buildings and spaces that don't yet exist; recording and optimizing the characteristics of an existing WLAN, and troubleshooting isolated spectrum problems that might be due to changes in any given area. Utilities that are built into a management system tend to vary in quality and practical value. The Location Manager module in Cisco's WLSE, for example, shows only simple pictures of a given area. On the other hand, the Wireless Control System (WCS) in the Cisco-acquired Airespace line is surprisingly similar to Ekahau's tools in user-friendliness, though WCS is not as robust.

Whether the goal is evaluating an existing network or planning a new one, good results depend on an accurate representation of walls, furniture, elevator shafts, trees and anything else that can influence the radio signals used in the WLAN. This is where the likes of Cisco's WLSE fall flat and Ekahau's product shines. Site Survey makes it easy to model an entire floor, city block or neighborhood with various attenuation sources.

Ekahau provides nine different building-related attenuation values as walls and such are plotted; sheetrock provides roughly 4.8 dB of loss per layer in the Wi-Fi frequencies, for example. It would be nice to see some attempt at more outdoor features like "big tree" or "wooden fence," though creative planners could probably use some of the existing choices to simulate a wide variety of objects. Lesser tools, like Cisco WLSE's Location Manager, have no provisions for simulating a real attenuation sources and thus are worthless at modeling the WLAN environment.However, Site Survey cannot meaningfully identify non Wi-Fi interference sources, such as microwave ovens, so users need another utility for spectrum analysis. A $3,500 suite should include at least some of this capability, which can be found in separate products, such as Wi-Spy's $99 MetaGeek and Cognio's $3,995 Spectrum Analyzer.

See It, Save It

Site Survey performs interactive surveys with any laptop that runs Windows XP or 2000. The user shows up onscreen as a dynamic line that moves across the electronic plan as she walks the area and clicks at locations of direction or speed changes. As this exercise continues, Site Survey gathers and assimilates data from the laptop's wireless NIC into a powerful collection of information, accessed over the simple user interface. You can survey existing APs or position any number of new ones in the environment. Each step can be recorded to form a cumulative survey as you move APs around.

These surveys show what is happening from the RF perspective in a given area, and allow all sorts of "what-ifs" to be exercised. What if I add an AP over there? What if a rogue AP on a specific channel pops up on the floor above? What if my network is under heavy user load? How does 802.11g coverage compare to 802.1a for an area? Ekahau and its competitors all answer these questions, but Site Survey's uncluttered GUI panels and well-placed windows make those answers easier to find, even when interfacing to a GPS unit for mapping large outdoor areas.Ekahau's suite has proven its real-world worth in several new buildings at Syracuse University that now have top-notch WLANs (first built on paper with Site Survey). As a network engineer at the university, I have used Site Survey to design effective WLANs in buildings yet to be constructed, with post-build verification proving the tool's ability to translate model to real WLAN.

Because nothing stays the same, any and all views are stored in highly detailed, effective reports that can be referenced later, or posted to a Web server. Unfortunately, reports are available only in HTML. AirMagnet Surveyor, by contrast, offers several file formats.

Good WLAN managers know that wireless shouldn't be a guessing game, and Site Survey 2.2 provides a multitude of answers for wireless site surveys and support. n

Lee Badman is a network engineer at Syracuse University. Write to him at [email protected].