About Wireless LANs
Wireless LANs can work in either of two (2) modes:
•
Ad-hoc
•
Infrastructure
Ad-hoc Mode
Ad-hoc mode does not require an Access Point or a wired (Ethernet) LAN. Wireless Sta-
tions (e.g. notebook PCs with wireless cards) communicate directly with each other.
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.
Note:
Access Points can only function in “Infrastructure” mode and can only communicate
with other Wireless Stations that 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 communicate
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 interfe-
rence, 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 performance. In the USA
and Canada, 11 channels are available. If using multiple Access Points, it is better if adja-
cent Access Points use different Channels to reduce interference.
•
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.)
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Summary of Contents for TEW-657BRM
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