AirLive WN-200R - Manual (Page 91)

AirLive WN-200R User’s Manual 87
Chapter 10 : About Wireless LANs
This Appendix provides some background information about using Wireless LANs (WLANs).
10.1 Modes
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 Stations (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.
Access Points can only function in "Infrastructure" mode,
and can communicate only with Wireless Stations which are
set to "Infrastructure" mode.
10.2 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 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.)
10.3 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 adjacent 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.)
• 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.