Appendix B - Troubleshooting
105
Different Access Points within an ESS can use different Channels. To reduce interference,
it is recommended that adjacent Access Points SHOULD use different channels.
As Wireless Stations are physically moved through the area covered by an ESS, they will
automatically change to the Access Point which has the least interference or best perform-
ance. This capability is called
Roaming
. (Access Points do not have or require Roaming
capabilities.)
Channels
The Wireless Channel sets the radio frequency used for communication.
•
Access Points use a fixed Channel. You can select the Channel used. This allows you to
choose a Channel which provides the least interference and best performance. For 802.11g,
13 channels are available in the USA and Canada., but 11channels are available in North
America if using 802.11b.
•
If using multiple Access Points, it is better if adjacent Access Points use different Chan-
nels to reduce interference. The recommended Channel spacing between adjacent Access
Points is 5 Channels (e.g. use Channels 1 and 6, or 6 and 11).
•
In "Infrastructure" mode, Wireless Stations normally scan all Channels, looking for an
Access Point. If more than one Access Point can be used, the one with the strongest signal
is used. (This can only happen within an ESS.)
•
If using "Ad-hoc" mode (no Access Point), all Wireless stations should be set to use the
same Channel. However, most Wireless stations will still scan all Channels to see if there
is an existing "Ad-hoc" group they can join.
WEP
WEP (Wired Equivalent Privacy) is a standard for encrypting data before it is transmitted. This
is desirable because it is impossible to prevent snoopers from receiving any data which is
transmitted by your Wireless Stations. But if the data is encrypted, then it is meaningless
unless the receiver can decrypt it.
If WEP is used, the Wireless Stations and the Wireless Access Point must have the same
settings.
WPA-PSK
Like WEP, data is encrypted before transmission. WPA is more secure than WEP, and should
be used if possible. The PSK (Pre-shared Key) must be entered on each Wireless station. The
256Bit encryption key is derived from the PSK, and changes frequently.
WPA-802.1x
WPA-802.1x - This version of WPA requires a Radius Server on your LAN to provide the
client authentication according to the 802.1x standard. Data transmissions are encrypted using
the WPA standard.
If this option is used:
•
The Access Point must have a "client login" on the Radius Server.
•
Each user must have a "user login" on the Radius Server.
•
Each user's wireless client must support 802.1x and provide the login data when required.
