User guide

134 Chapter 10: Device Detection
AirMagnet Spectrum XT User Guide
Motion Detector
Motion detectors are devices that use a variety of methods to determine if a body of a
significant size is coving through an area, usually as part of a security or energy management
system. While most models use infrared detection system, some newer models incorporate a
microwave detection system. In some models, this microwave detection system transmits on a
narrow band of frequency in the 2.4GHz band. While only active at times of motion detection,
in areas of high pedestrian traffic, or areas of high WLAN traffic, these devices present the
possibility of isrupting WLAN traffic of the transmitting frequency of the device corresponds
with the channel the WLAN is operating on. AirMagnet Spectrum XT will detect S-Band radar
based motion detectors that are operating in the environment.
RF Spectrum Pattern
Below is a sample of what the spectrum pattern for a motion detector would look like in a
relatively noiseless 2.4GHz spectrum.
Figure 10-13: Interference Source - Motion Detector
Impact on 802.11 WLAN
The impact on 802.11 networks depends on the amount of pedestrian traffic near the motion
detector.
• Because this technology only transmits a signal when the correct parameters for motion
detection are met, in areas of low pedestrian traffic, the impact on a WLAN network will be
low. The device may cause intermittent interference only if it is transmitting on a frequency