increased demands for mobility and flexibility in our daily life are demands
that lead the development from wired LANs to wireless LANs (WLANs).
electromagnetic radio waves to transport data between computers in a Local Area
Network (LAN), without the limitations set by ―hard wired network cable or
phone wire connection‖. Whilst simple optical links are commercially available,
radio is presently more useful since it is not strictly restricted to
waves are often called radio carriers when they are used to carry information.
The data to be transported is superimposed on the radio carrier by various
modulation techniques which allow the data to be faithfully reconstructed at
the receiving end. Once data is superimposed (modulated) onto the radio
carrier, this combined ―radio channel‖ now occupies more than a single
frequency since the frequency components or spectra of the modulating data add
frequency bandwidth to the basic carrier (in direct proportion to its
information content or bit rate). The frequency range which is needed to
accommodate a radio signal with any given modulation bandwidth is called a
channel. Radio receiver techniques can select one radio channel while
efficiency rejecting signals on other frequencies. Many radio signals to and
from many users can thereby co-exist in the same place and time without
interfering with each other if the radio waves are transmitted at minimum
necessary power within different radio channels.
ADVANTAGES OF WLAN OVER WIRED LAN
: With in
radio coverage nodes can communicate without further restriction.
ad hoc network allow communication without planning whereas wired network needs wiring plans.
Design : Wireless
Network allows for the design of small independent devices.
network can survive disaster. If the wireless devices survive people can communicate.
Cost : Adding
additional users to a wireless network will be increase the cost. But where as with fixed network
addition of an user will lead into unplugging and plugging. Wireless
communications do not wear out.
Wireless offers lower quality than
that of wired. The reasons are
The lower bandwidth due to limitations
in radio transmission.
High error rate due to interference.
Higher delay due to error correction
and detection mechanisms.
PROPRIETARY SOLUTION :
Many companies have comeup
with proprietary solutions
offering standardized functionality.
This is due to slow standardization
The wireless products need to comply
with national regulations.
WLAN are limited to low power senders and
certain license free frequency hand which are not same world wide.
SAFETY AND SECURITY :
The radio waves are used for data
transmission. They will interfere with other equipment. Precaution have to be
taken to prevent safety hazards.i
· As it is via radio transmissions
eaves dropping is possible.
operation : While the product is being sold in all the
countries, national and
international frequency regulations should be considered.
communicating via WLAN are also wireless devices. These devices run on battery power – while designing a WLAN these
aspects should also be considered.
free Operation : The equipment must operate in a license free band such as 2.4 GHz ISM Band
Robust Transmission Technology : WLAN operate under difficult
As they are radio transmission many other electrical devices can interfere with
Spontaneous Co-operation : WLAN should not require complicated startup routines , but should run spontaneously after
use : WLAN‘s are mad for simple use. They should be like plug and play.
of Investment : For transmission from wired to wireless, simple bridging should be enough to
and Security : WLAN should be safe to operate. When low radiation are used. The network should consider
user privacy and security.
applications should continue to run over WLAN with trade off to higher delay and lower bandwidth.