User guide

AirMagnet Spectrum XT User Guide
Chapter 10: Device Detection 131
Digital Video Monitors
A digital video monitor is typically made up of three components: a video camera, a
transmitter to send the signal, and a receiver to receive the signal. The system works in such a
way that the wireless camera transmits video from the built-in transmitter to the receiver,
which is connected to a display device (monitor) or a recording device.
Most digital video monitors operate on the 2.4-GHz frequency – an unlicensed radio band also
used by 802.11b/g WLANs, cordless phones, Bluetooth devices, and microwave ovens, etc.
Like the other non-WiFi devices operating in the 2.4-GHz frequency band, digital video
monitor installed in close proximity of an 802.11b/g WLAN can interfere with the normal
operation of the WLAN. Unlike the other RF interfering devices operating in the 2.4-GHz
band, radio signals from the transmitter of a digital video monitor can travel a relatively long
range which varies from 200 to 700 feet (line of sight), depending on the physical conditions of
the site. Typically, multiple cameras are needed in order to provide full, overlapping coverage
of one site. To make matters worse, digital video monitors installed in homes and businesses
are left on all the time. And so is the RF interference they cause to the 802.11 WLAN close to
them.
RF Spectrum Pattern
Digital video monitors come in all shapes and sizes. They include wireless surveillance
cameras, spy cameras, etc. They are widely used in homes and businesses where the 802.11
WLAN is deployed. Their presence can cause serious performance issues in the WLAN. The
figure below shows the RF spectrum pattern of a wireless camera using the 2.4-GHz
frequency band.
Figure 10-11: RF spectrum pattern of a digital video monitor
Impact on 802.11b/g WLAN
Because digital video monitors are widely used in homes and businesses where WLANs are
deployed, radio signals from these devices have long been identified as a source of RF
interference to 802.11b/g WLANs in these settings. They can significantly slow down Internet
applications such as Web file download and surfing.
Recommended Courses of Action
Once the interfering wireless security cameras are successfully identified, the following
actions are recommended to minimize or eliminate the RF interference they cause to the
802.11 WLAN.