IronPort Systems ZyAIR B-4000 - Manual (Page 159)

ZyAIR B-4000 Hot Spot Gateway
Wireless LAN 18-3
18.2 Wireless LAN Basics
This section provides background information on Wireless LAN features.
18.2.1 Channel
A channel is the radio frequency(ies) used by IEEE 802.11b wireless devices. Channels available depend
on your geographical area. You may have a choice of channels (for your region) so you should use a
different channel than an adjacent AP (access point) to reduce interference. Interference occurs when radio
signals from different access points overlap causing interference and degrading performance.
Adjacent channels partially overlap however. To avoid interference due to overlap, your AP should be on a
channel at least five channels away from a channel that an adjacent AP is using. For example, if your
region has 11 channels and an adjacent AP is using channel 1, then you need to select a channel between 6
and 11.
18.2.2 WEP Encryption
WEP (Wired Equivalent Privacy) encrypts data frames before transmitting over the wireless network. WEP
encryption scrambles the data transmitted between the wireless stations and the access points to keep
network communications private. It encrypts unicast and multicast communications in a network. Both the
wireless stations and the access points must use the same WEP key for data encryption and decryption.
WEP degrades performance.
18.2.3 RTS/CTS
A hidden node occurs when two stations are within range of the same access point, but are not within range
of each other. The following figure illustrates a hidden node. Both stations (STA) are within range of the
access point (AP) or wireless gateway, but out-of-range of each other, so they cannot “hear” each other,
that is they do not know if the channel is currently being used. Therefore, they are considered hidden from
each other.