Watchguard Firebox SOHO 6 Wireless, Руководство пользователя

Страница: 30 / 208

8 WatchGuard Firebox SOHO 6 Wireless
Noise Level (watts)
The more in-band RF noise there is the less data can be
transmitted over a given channel (wireless link). The noise
level is primarily due to three factors:
First, there is a minimum level of background noise due to
the ambient temperature of the channel (atmosphere) and
the bandwidth.
Second, the 802.11b receiver will have an innate noise level
due to its own components operating temperature.
Third, there are many unlicensed transmitters using the
same frequency bands as 802.11. Some of these are:
- Cordless phones,
- Other 802.11b devices operating on adjacent channels.
Note that only channels 1, 6, and11 are unique. All other
channels overlap because while the center frequencies
increment by 5MHz per channel, the bandwidths are
22MHz.
- Microwave ovens,
- Sodium type lighting systems (fusion lamps),
- Arc welders (broadband spark gap transmitters)
- Blue-Tooth transmitters. Note that a Blue-Tooth
transmitter operates at lower power levels and would
need to be near an 802.11b receiver to interfere with it.
- Industrial, Scientific, and Medical equipment can also use
these bands.
Signal Strength (watts)
The signal strength depends primarily on:
- How much RF signal power is transmitted