Installation guide

25
Wi-Fi Location-Based Services—Design and Deployment Considerations
OL-11612-01
Cisco Location-Based Services Architecture
Accuracy and Precision of the Cisco LBS Solution
With proper deployment according to the best practices outlined both in this white paper as well as those
contained within the documents referenced in Reference Publications, page 5, the accuracy and
precision of the Cisco LBS solution in indoor deployments is represented as follows:
• Accuracy of less than or equal to 10 meters, with 90 percent precision
• Accuracy of less than or equal to 5 meters, with 50 percent precision
In other words, given proper design and deployment of the system, the error distance between the
reported device location and the actual location should, in 90 percent of all reporting instances, be
10 meters or less. In the remaining 10 percent of all reporting instances, the error distance may be
expected to exceed 10 meters. Note that these specifications apply only to solutions using RF
Fingerprinting; namely, the use of a WCS licensed for location usage (with or without a location
appliance).
For applications that require better performance than an accuracy of 10 meters with 90 percent precision,
the Cisco LBS solution can deliver accuracy of 5 meters or less but with 50 percent precision. Stated
another way, in 50 percent of all reporting instances, it can be reasonably expected that the error distance
between the reported and the actual location exceeds 5 meters. The location inspection tool can display
various levels of accuracy and precision from 2 m to 100 m along with which areas of your environment
can meet these accuracy levels. The location inspection tool is discussed in Inspecting Location Quality,
page 76.
Which Devices Can Be Tracked
WLAN Clients
WLAN clients or Wi-Fi 802.11 active RFID tags that are probing and are associated or attempting
association with your location-aware LWAPP enabled wireless LAN infrastructure can be tracked with
the Cisco LBS solution. This includes asset tags such as PanGo Locator LAN RFID tags.
Keep in mind that client behavior has a significant impact on the ability of the location appliance to
provide accurate location tracking. The more consistent the client is in transmitting probe responses, the
better the ability of the system to provide accurate location tracking. If a client suspends transmitting
probe requests across all channels, or transmits them at abnormally low or abnormally high power,
location accuracy can be degraded. One way of minimizing exposure to this type of unpredictable client
behavior is to standardize on clients that have been certified as complying with the client CCX
specification version 2 or better, and enabling the use of CCX Location Measurement on all controllers,
as shown in Figure 10. Enabling CCX Location Measurement enables access points to transmit
broadcast messages that cause CCX clients to reliably transmit probe requests, facilitating the ability of
the system to accurately track these devices in a consistent fashion.