Appendix B
About Wireless LANs
This Appendix provides some background information about using Wireless LANs (WLANs).
Modes
Infrastructure Mode
In Infrastructure Mode, one or more Access Points are used to connect Wireless Stations (e.g. Notebook PCs with wireless cards) to a wired (Ethernet) LAN. The Wireless Stations can then access all LAN resources.
Access Points can only function in "Infrastructure" mode, and can communicate only with Wireless Stations which are set to "Infrastructure" mode.
BSS/ESS
BSS
A group of Wireless Stations and a single Access Point, all using the same ID (SSID), form a Basic Service Set (BSS).
Using the same SSID is essential. Devices with different SSIDs are unable to com- municate with each other.
ESS
A group of Wireless Stations, and multiple Access Points, all using the same ID (ESSID), form an Extended Service Set (ESS).
Different Access Points within an ESS can use different Channels. In fact, 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 performance. 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 perform- ance. In the USA and Canada, 11 channels are available. If using multiple Access Points, it is better if adjacent Access Points use different Channels to reduce inter- ference.
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