OVERVIEW
WLAN is a network technology which has all
capabilities of a wired Local Area Network(LAN), but without
any wires. It uses radio waves to transmit/receive information.
The leading WLAN products use radio waves, typically in the
license-free 2.4GHz band, to communicate digital information
through the open air.
Currently there are three mail WLAN standards:
- IEEE 802.11b (Wi-Fi): 11 Mb/s data rate at 2.4 GHz
- IEEE 802.11a: 54 Mb/s data rate at 5 GHz
- IEEE 802.11g: 54 Mb/s data rate at 2.4 GHz
WLAN COMPONENTS
The principle of WLAN is to establish quick
radio links between terminals connected to networks.This technology
is facilitated by a number of components:
- PC Card: A Network adapter and integrated
antenna that plugs into a peer, client, or server system’s
expansion card slot. Clients can be desktops and laptop
computers, file servers, printers, tape backup systems,
and other office automation equipment.
- Ethernet Adapter: For peers, clients,
or servers with pre-existing Ethernet network interface
cards (NICs) or serial ports. This external module converts
a wired client into a wireless client. Ethernet adapters
plug directly into the client’s Ethernet NIC.
- Access Point (AP): An intelligent wireless
“hub”. The access point manages wireless data
traffic and controls the communication within the WLAN
and between the wireless clients and the wired network.
- Bridge: These components use antennas
to “bridge” across long distances, linking
LANs wirelessly between buildings or within a building
and communicate information between access points. Bridges
can be used in a point-to-point or point-to-multipoint
configuration.
- Antennas: These wireless signal boosters
come in a number of formats specialized for the range
and direction the wireless signal must take and for various
strengths. Some antenna are integrated (e.g., in the wireless
PC card and station adapter); others are external (e.g.,
wall-mounted or roof-mounted extension of a wireless bridge)
for building-to-building communications.
- Signal Amplifiers: Spanning very long
distances (e.g., between buildings) may require the use
of signal amplifiers to bolster the wireless radio signal.
Amplifiers are inserted in-line between the access point
or bridge and antennas.
WLAN NETWORK DEPLOYMENT
Infrastructure Mode : In this mode, Access
Points are linked to a wired LAN. A typical Infrastructure
mode deployment of WLAN is depicted below:
Ad-Hoc Mode: An Ad-Hoc mode is an on-demand
WLAN without any access points. A typical Ad-Hoc mode deployment
of WLAN is depicted below:
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