Watchguard Firebox SOHO 6 Wireless User Manual page 35

Noise level (Watts)
An increase of the noise level within the frequency range of the
system reduces the channel capacity. The noise level is determined
by three factors:
• Background noise caused by the ambient temperature of the
atmosphere at the frequency range of the system
• Noise caused by the operating temperature of the components
of the 802.11b receiver
• Interference caused by other transmitters using the same
frequency range, including:
- Cordless phones
- Other 802.11b devices operating on adjacent channels
(Only channels 1, 6, and 11 are unique. The other channels
overlap: the bandwidth of each channel is 22 MHz and
the center frequencies differ by only 5 MHz per channel.)
- Microwave ovens
- Sodium-type lighting systems (fusion lamps)
- Arc welders (broadband spark-gap transmitters)
- Blue-Tooth transmitters (A Blue-Tooth transmitter
operates at a lower power level than an 802.11b device. To
cause interference, the Blue-Tooth transmitter would need
to be very close to an 802.11b receiver.)
- Industrial, scientific, and medical equipment (These
devices may also operate in this frequency range.)
Signal strength (Watts)
The signal strength is determined by the following factors:
• Power of the RF signal that is transmitted and received
User Guide
Understanding IEEE 802.11b Wireless Communication
9