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AeroScout, a well-known player in the Wi-Fi location market, focuses less on pinpoint accuracy, more on integrating with Wi-Fi networks to provide ubiquitous visibility into the whereabouts of assets and people. It has arguably the most comprehensive set of hardware and software products of any location vendor, offering tags in multiple form factors as well as chokepoints for sending alerts and a locationing engine that can process location from its tags based on TDOA (time difference of arrival) in addition to RSSI (received signal strength indication).
AeroScout's tags, which it developed in-house, differ from those of its main competitor. Rather than have a tag take readings, associate with an access point, and then communicate with a location engine, AeroScout's tags regularly "chirp" or "beacon" a 416-bit 802.11 frame. This approach reduces tag/access point interaction to a simple unidirectional packet. No state for the access point to maintain and no IP address required--and less radio time means longer battery life.
On the other hand, the Wi-Fi infrastructure needs to be able to listen for and interpret this packet, despite the lack of association, and send it on to the locationing engine. This requires enterprise Wi-Fi gear vendors to buy into the concept and add support for AeroScout's message. Fortunately, according to AeroScout, more than 95% of enterprise access points support its tags today. For Cisco Systems Lightweight Access Point Protocol, or LWAPP, environments, location information is sent to the Cisco Location Appliance and Wireless Control System rather than AeroScout's engine.
Another caveat is that tag messages can be cloned. Because there's no authentication or two-way verification, once tag communication is captured, it can be played back on any device. AeroScout says its engine can filter fake messages and toss erroneous readings.
A TAG FOR EVERY PURPOSE
Tags are available with a variety of mounting options in multiple form factors, from ruggedized packages to small portable units and personnel badges. In AeroScout's T3 model, motion sensors conserve battery life when the asset is stationary. Optional temperature sensors can help ensure that sensitive items are within the proper environment. Two call buttons are standard on the T3 model. The replaceable battery operates up to four years, and available extended batteries may last as long as eight years. AeroScout's T3 tag also includes infrared support for over-the-air firmware upgrades. Tags can be set to turn themselves on or off as they go through chokepoints, as when an employee is leaving the building, or to sense if an expensive item walks out the door.
Completing the picture is AeroScout's engine, which receives location reports and calculates the positions of tags. AeroScout's own algorithms use RSSI, a value appended by the access point or WLAN controller to the tag's beacon, to calculate location. Data on the tag's previous position, the AP's location, and fingerprinting helps tighten accuracy to perhaps 3 meters, depending on environment and the location and density of APs. We don't see scalability as a concern. A single engine can handle 500 location reports per second, and multiple engines can feed into one MobileView server, described later.
AeroScout is a key Cisco partner, unlike its main competitor, Ekahau. AeroScout's Web-based MobileView shares with Cisco's Location Appliance and Wireless Control System a common set of management information, including site maps. Cisco often bundles its location appliance into larger enterprise WLAN deals but doesn't make tags itself. AeroScout's tags have passed Cisco's CCX certification program for Wi-Fi tags.
ON THE GO
One powerful feature is filtering. Say a nursing supervisor wants to see patient beds but not medical equipment, while a repair person wants to track all heart monitors. Using MobileView, zones can be created and rules assigned such that a supervisor can be paged when there are too few nurses on a certain floor, or an alarm may ring when gear leaves the grounds.
AeroScout also offers a SOAP API for third-party integration and bidirectional data exchange. The company emphasizes its MobileView product, preferring that customers leverage its MobileView client rather than a third-party application. That said, AeroScout also supports exporting location and events into other systems that may not currently have a visual component. Prospective customers might consider this bias a gating factor if they have a unique business application or don't want to be locked into AeroScout's product line.
The company seems sound. Privately held and founded in 1999, AeroScout has raised $55.5 million in funding over three rounds. It has 120 employees and focuses primarily on health care, manufacturing, and logistics/transportation. According to In-Stat, in 2006 the company led the industry by shipping 100,000 Wi-Fi tags.
In light of Cisco's dominance in the enterprise WLAN market, AeroScout's partnership provides an opportunity to generate real volume on tags. However, AeroScout's Engine is supplanted by Cisco's own location appliance in Cisco LWAPP environments, reducing the stickiness AeroScout has with customers--only 30% of the enterprise Wi-Fi market is not owned by Cisco.
Finally, we have to devote a few words to chokepoints, also called exciters. By using strategically placed readers or triggering devices, location accuracy and speed of identification can be dramatically improved. When a tag passes within range of a 125-KHz exciter, the tag emits a short burst of Wi-Fi data that includes the unique identification of that exciter. This is not dynamic information: Each exciter has a unique signature that's programmed into the tag to be associated with a unique value. Without an exciter, it may take several minutes before the tag chirps and the location is updated. The interval time can be brought down to several seconds, but at the expense of battery life.
This story was updated Nov. 27 to clarify AeroScout's third-party integration stance and the number of call buttons on the T3 model.