User's Guide

resolution in 802.11 devices, the positioning resolution and stability tends to be better near receivers/
sensors. To achieve accurate results, follow these guidelines:
• Place at least three independent sensors on the same floor plan so the system can capture the RSSI
values.
• Place a sensor in each area where accurate resolution is required or to increase overall sensor
density to ensure high RSSI values.
Considerations for Sensor Placement with Location Tracking
Every site is unique in terms of actual sensor coverage; this section merely describes sensor placement
and respective coverage in a simplified way. Actual signal propagation is a very complex issue due to
environmental factors like the reflection/absorption properties of materials (walls, furniture), large
moving object, etc.
• Sensors should be placed in corners, preferably in a way which minimizes random fluctuations in
signal strength caused by people moving around, opening / closing doors, windows or large objects
which may be moved during operation, etc.
• Sensors should not be placed in a straight lineto eliminate the possibility of having two or more
similar RSSI values from sensor combinations for dierent location, combined coverage areas for the
sensors should not be symmetric.
• Place additional sensors in areas where accuracy is importantto achieve repeatable and consistent
positioning resolution, sensors should be placed so that they measure unique signal strengths and
sensor combinations for each location considered significant.
IDS versus Location Tracking
Ideal sensor placement for Wireless IDS diers from that for Location Tracking.
Example 1
You have a small oce of 10,000 sq. ft. For Wireless IDS/IPS you would only need 1 sensor; to maximize
the coverage it makes sense to place the sensor in the center of the building. When location tracking is
need in this same scenario, a minimum of 3 sensors for each floor plan would be required, and
recommended placement is at the corners.
Example 2
You have a multi-floor building with 3 floors. Depending on floor construction the RF may travel
through each floor. If only Wireless IDS/IPS is required, you may be able to leverage detection through
the floor and ceiling and place sensors on every other floor. Depending on the floor characteristics, you
may need a sensor on each floor, however it may make sense to o-set each sensor on each floor and
Planning Your Sensor Placement
Legacy Content
1384 Extreme AirDefense User Guide for version 10.5.