Page 19 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 1: Introduction to Wireless Networks

Wireless LAN or Wireless Local Area Network is a term to refer to a Local Area Network that does Notes
not need cables to connect the different devices. Instead, radio waves are used to communicate.
Technologies that can be used to do that include IEEE 802.11 and Bluetooth.

Benefits of Wireless LANs

z z People can access the network from where they want; they are no longer limited by the
length of the cable
z z Some cities have started to offer Wireless LANs. This means that people can access the
internet even outside their normal work environment, for example when they ride the
train home.
z z Setting up a wireless LAN can be done with one box (called Access point). This box can
handle a varying number of connections at the same time. Wired networks require cables
to be laid. This can be difficult for certain places.
z z Access points can serve a varying number of computers.

Disadvantages of Wireless LANs

z z Wireless LANs use radio waves to communicate. Special care needs to be taken to encrypt
information. Also the signal is much worse, and more bandwidth needs to be spent on
error correction.
z z A typical IEEE 802.11 access point has a range of meters from where devices can connect.
To extend the range more access points are needed.

z z There are many reliability problems, especially those connected to interference from other
devices.

z z Wireless LANs are much slower than wired ones; this may not matter for most users
though, because the bottleneck in a home network is usually the speed of the ADSL line
(used to connect to the Internet)

Technologies used

Today, most technologies used for WLANs use Orthogonal Frequency Division Multiplexing.
This means that several frequencies are used at the same time. Signals that are close to each
other, but that belong to different channels do not disturb each other, as they use different coding
schemes. Depending on the material used, it is possible to cover between 30 metres and 100
metres indoors; outoors, the range is about 100-300m, if there are no obstacles.
A wireless LAN (WLAN or WiFi) is a data transmission system designed to provide location-
independent network access between computing devices by using radio waves rather than a
cable infrastructure [IEEE 802.11 Wireless LANs, Technical paper].
In the corporate enterprise, wireless LANs are usually implemented as the final link between the
existing wired network and a group of client computers, giving these users wireless access to the
full resources and services of the corporate network across a building or campus setting.

The widespread acceptance of WLANs depends on industry standardization to ensure product
compatibility and reliability among the various manufacturers.
The 802.11 specification [IEEE Std 802.11 (ISO/IEC 8802-11: 1999)] as a standard for wireless
LANS was ratified by the Institute of Electrical and Electronics Engineers (IEEE) in the year 1997.
This version of 802.11 provides for 1 Mbps and 2 Mbps data rates and a set of fundamental
signaling methods and other services. Like all IEEE 802 standards, the 802.11 standards focus on

LOVELY PROFESSIONAL UNIVERSITY 13