User's Guide

Physical and Electromagnetic Interference
Many devices can interfere with sensors monitoring of the wireless network, including:
• Cordless phones and headsets
• Bluetooth devices
• Microwave ovens
• Consumer cordless devices (for example, surveillance cameras, baby monitors, and video
transmission extenders).
Device Placement Considerations
Keep the following considerations in mind when you place devices:
• Device Density
• Device Requirements per Area
• Desired Monitoring and Intrusion Protection Functionality
• Assets to be Protected
• Sensor Quantity and Placement
• Power and Data Cabling
Device Density
You should consider the density of 802.11a, b, g, and n devices:
• Support of a high number of users
• Support of high bandwidth consumption
• Localization of wireless network service.
The sensors should be separated by at least 10 feet from any installed APs to avoid radio defense. The
active transmissions of an AP can desensitize the sensor receiver radio on the same channel when
placed in close proximity of an AP.
Device Requirements per Area
While a single AirDefense sensor can monitor a very large area, distributing multiple sensors in such an
area can provide a much better idea of where a rogue device is physically located. By comparing the
RSSI values each sensor detects, you can find the device more easily. Three or more sensors are
required for the location tracking to work because triangulation is a requirement for the location
tracking to work.
Desired Monitoring and Intrusion Protection Functionality
Your decisions about sensor placement should also take into account what functionality you plan to use.
Five important functions that are dependent on sensor density or placement are:
• WEP Cloaking—For eective WEP Cloaking, several sensors should be deployed around the
perimeter of a building. Higher sensor density will typically yield better protection for your legacy
encryption devices.
• Location Tracking—To track a device, the device must be observed by three or more sensors on the
same floor plan. Higher sensor density will typically yield more accurate results.
Physical and Electromagnetic Interference
Security
846 Extreme AirDefense User Guide for version 10.5.