Technical data

328 Meru System Director Configuration Guide © 2012 Meru Networks, Inc.
have the same BSSID, thus virtualizing the network from the client's perspective. When
Virtual Ports are used, each client sees a different BSSID, appearing to get its own private
AP. See also ESSID.
C
Co-channel
Interference
Radio interference that occurs when two transmitters use the same frequency without
being closely synchronized. Legacy wireless systems cannot achieve this kind of synchro-
nization, so access points or cell towers that transmit on one channel must be spaced far
apart. The result is coverage gaps that must be filled in with radios tuned to another
channel, resulting in an inefficient and complex microcell architecture. Air Traffic Control
technology avoids co-channel interference by tightly synchronizing access point transmis-
sions, enabling that adjacent APs to use the same channel.
Channel
Bonding
The combination of two non-overlapping 20 MHz. channels into a single 40 MHz. channel,
doubling the amount of data that can be transmitted in a given time but halving the
number of available channels. Along with MIMO, it is a key innovation in the 802.11n stan-
dard.
Channel
Layering
Wireless LAN architecture in which several Virtual Cells are located in the same physical
space but on non-overlapping channels, multiplying the available capacity. This additional
capacity can be used for redundancy or to support higher data rates or user density. It can
be enabled through multiple radios on one AP or by using multiple AP close together, so
the total capacity is limited only be the number of non-overlapping channels available.
Channel Reuse
A pattern in which different APs can use the same channel. In microcell networks, such
APs need to be placed far apart to avoid co-channel interference, meaning that contiguous
coverage requires multiple channels. In networks using Air Traffic Control technology, the
same channel can be reused throughout the network, meaning that only one channel is
required and others are left free for other purposes.
CHAP
Challenge Handshake Authentication Protocol. An authentication protocol that defines a
three-way handshake to authenticate a user. CHAP uses the MD5 hash algorithm to
generate a response to a challenge that can be checked by the authenticator.
CLI
Command-line interpreter. On a controller and other units, this is similar to a command
shell for giving instructions.
client
Any computer connected to a network that requests services (files, print capability) from
another member of the network.
client devices
Clients are end users. Wi-Fi client devices include PC Cards that slide into laptop
computers, mini-PCI modules embedded in laptop computers and mobile computing
devices, as well as USB radios and PCI/ISA bus Wi-Fi radios. Client devices usually commu-
nicate with hub devices like access points and gateways.
collision avoid-
ance
A network node characteristic for proactively detecting that it can transmit a signal
without risking a collision.
controller A device that is responsible for configuring and integrating the access points in a WLAN.