User's Guide

surrounded by parking areas, you may want to consider additional sensors in the back for complete
protection.
• Channel coverage - A single sensor should not be required to cloak more than 3 s at a time.
For eective cloaking there must be sucient cha WEP frames to confuse the statistical WEP
cracking tools. At the same time, the sensors must perform regular Wireless IPS scanning on other
channels. The sensors are designed to intelligently adjust their frequency scanning patterns.
However, to maximize cloaking eectiveness and scan all other channels for possible intrusions,
sensors should not be expected to cloak more than three APs, or more specifically three unique
communication channels at a time.
For Adequate Protection
Typically it will take several sensors deployed at the perimeter of the building to adequately protect all
wireless devices with WEP Cloaking. This also implies that, even in small stores, it may take more than
one sensor for adequate WEP Cloaking protection; the higher the density of sensors you deploy, the
better your legacy encryption devices will be protected. Any deployment should start with a site survey
or RF simulation of the WLAN environment, followed by a mapping of sensor coverage to access point
coverage of unique channels.
Sensor Placement with Location Tracking
Sensor density and sensor placement are the most important factors regarding overall positioning
resolution. Due to the nature of high frequency signals (2.4 GHz and 5 GHz) and limited signal strength
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.
Sensor Placement with Location Tracking
Security
850 Extreme AirDefense User Guide for version 10.5.