Wireless Coverage - Extreme Networks Altitude 4700 Series Product Reference Manual

Introduction
digital data signal is encoded onto carriers using a DSSS chipping algorithm. The radio signal propagates
into the air as electromagnetic waves. A receiving antenna (on the MU) in the path of the waves absorbs
the waves as electrical signals. The receiving MU interprets (demodulates) the signal by reapplying the
direct sequence chipping code. This demodulation results in the original digital data.
The Access Point uses its environment (the air and certain objects) as the transmission medium.The
Access Point can either transmit in the 2.4 to 2.5-GHz frequency range (802.11b/g/n radio) or the 5 GHz
frequency range (802.11a/n radio), the actual range is country-dependent. Extreme Networks devices,
like other Ethernet devices, have unique, hardware encoded Media Access Control (MAC) or IEEE
addresses. MAC addresses determine the device sending or receiving data. A MAC address is a 48-bit
number written as six hexadecimal bytes separated by colons. For example: 00:04:96:44:51:90. Also see
the following:

"Wireless Coverage"

●
"MAC Layer Bridging"
●
"Content Filtering"
●
"DHCP Support"
●
"Media Types"
●
"Direct-Sequence Spread Spectrum"
●
"MU Association Process"
●
"Operating Modes"
●
"Management Access Options"
●
"MAC Address Assignment"
●
Wireless Coverage
An Access Point establishes an average communication range with MUs called a Basic Service Set (BSS)
or cell. When in a particular cell, the MU associates and communicates with the Access Point
supporting the radio coverage area of that cell. Adding Access Points to a single LAN establishes more
cells to extend the range of the network. Configuring the same ESSID (Extended Service Set Identifier) on
all Access Points makes them part of the same Wireless LAN.
Access points with the same ESSID define a coverage area. A valid ESSID is an alphanumeric, case-
sensitive identifier up to 32 characters. An MU searches for an Access Point with a matching ESSID and
synchronizes (associates) to establish communications. This device association allows MUs within the
coverage area to move about or roam. As the MU roams from cell to cell, it associates with a different
Access Point. The roam occurs when the MU analyzes the reception quality at a location and determines
a different provides better signal strength and lower MU load distribution.
If the MU does not find an Access Point with a workable signal, it can perform a scan to find any AP.
As MUs controller APs, the AP updates its association statistics.
The user can configure the ESSID to correspond to up to 16 WLANs on each 802.11a/n or 802.11b/g/n
radio. A Wireless Local Area Network (WLAN) is a data-communications system that flexibly extends the
functionalities of a wired LAN. A WLAN does not require lining up devices for line-of-sight
transmission, and are thus, desirable. Within the WLAN, roaming users can be handed off from one
Access Point to another like a phone system. WLANs can therefore be configured around the needs of
specific groups of users, even when they are not in physical proximity.
40
Altitude 4700 Series Access Point Product Reference Guide