Network Computing is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Wi-Fi Location Rolling Review: Ekahau Bets On Active Tags: Page 2 of 4

THE UPSHOT
CLAIM: 
Ekahau provides the best accuracy via a tag-centric approach to calculating location, without exciters or choke points. This two-way data flow also facilitates greater interactivity between tags and management system.
CONTEXT: 

With Wi-Fi locationing, your WLAN enables asset tracking while tightening security by extending NAC to tailor access based on a user's location. Partnerships and integration with corporate applications is key for usability.
CREDIBILITY: 
Ekahau is taking risks by emphasizing Wi-Fi as a superior platform and by its heavy tag focus. Its infrastructure-agnostic approach makes the system very palatable for heterogeneous environments, however.

The debate over whether an associated or a beaconing approach is superior is just one element in the technical sparring going on among Wi-Fi location vendors. No one disputes that a two-way associated system allows for niceties such as visual and audible alerts on tags as well as two-way text messaging and wireless, remote software updates. Less clear is the model's effect on performance, security, and management complexity.

In this case, the devil is in the details, and there are lots of them.

Physics tells us that RF signals flow equally well from an access point to a tag as from a tag to an AP. If a tag operates in associated mode and has a granular and well-calibrated receiver, those advantages are tempered by dynamic changes in environmental conditions and output power variations among APs. Many enterprise WLAN vendors support dynamic RF control, which means output power can change over time, but Ekahau says that doesn't significantly affect accuracy. Most significant to the accuracy claims of the tag-centric approach is the use of site survey software to gather the actual state of the RF environment, calibrate it, and feed that into a realistic location algorithm. Ekahau argues that poll-based systems that require a controller to look to each access point and gather a client's RSSI incurs a time-skewing effect that a client-centric approach doesn't have.

However, there are also beaconing systems that send one or more beacons out on multiple channels that are nearly instantaneously received and passed on to the location engine.

Barring a potential performance advantage for Ekahau in regards to a tag-centric approach, what other effect might associated mode operation have on a network? First, in associated mode, each tag needs to associate and authenticate, which requires at least four 802.11 frames. Then there's the method of updating location. A beaconing tag normally sends out a single beacon or packet every location update, but associating tags send out many more packets. Again, not a notable concern in small deployments, but if your WLAN uses a centralized data plane and/or operates over a WAN, you could feel a hit.