Wireless Local Area Network

workablejeansMobile - Wireless

Nov 21, 2013 (3 years and 9 months ago)

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A Wireless Local Area Network (WLAN) is a
network that interconnects devices using radio
waves.


Wireless networking technologies allow
devices to communicate to each other without
using cables
or wires.




The most common wireless technologies are:



The most common wireless technologies are:

Bluetooth

Infrared Direct Access (IrDA)

Shared Wireless Access Protocol (SWAP)

Wireless Ethernet Compatibility Alliance (WECA)






Bluetooth allows low bandwidth, short
-
range
(up to
10
m) wireless communication using the
2.4
GHz unlicensed
ISM (Industrial, Scientific
and Medicine
) band. This technology is used to
connect two
or more
devices in a home
network and can support data rate up to
1
Mbps. An example of a
Bluetooth
iapplication

is a laptop making call over a cellular phone.
Another example is cordless keyboard,
mouse
and
speaker connected to a Personal Computer.


This technology allows devices to communicate using
infrared light at a speed up to
4
Mbps. Infrared

light cannot pass through the walls or obstacles. So,
devices can only communicate with each other, if

they are in direct line of sight. A simple example of
IrDA application is a laptop sending print documents

to a printer using infrared port. Most of the new
mobile phones and laptops have infrared port. You
can

also transfer data (like address book and calendar)
between a mobile phone and a laptop through

infrared port, if both devices have infrared port.


.

Shared Wireless Access Protocol (SWAP) is a
standard developed by an alliance of businesses
called
HomeRF

Working Group. The
HomeRF

Working Group allows data and voice
transmission using
2.4
GHz ISM
band. It supports
data rate up to
1.6
Mbps within the range of
30
m.






The IEEE specifications of the
802.11
standard for wireless
LANs have provided a big boost to the
WLAN industry
. These
specifications allowed the creation of large scale commercial
WLANs, but they do
notcertify

WLANs’
equipments

The IEEE
802.11
b was the commonly used standard before
2002
. It uses the
2.4
GHz radio
spectrum and
supports data rate
up to
11
Mbps. The new IEEE
802.11
a standard operates in the
5.2
GHz
-

5.8
GHz spectrum
and supports up to
54
Mbps rates.
This technology allows a radio transmitter (Wireless Network
Card) to spread data

packets over a fixed range of the frequency band. Another
device carrying a radio receiver (
Wireless
Network

Card)

These WLANs can transmit data within a radius of
300
feet
indoors and
1000
feet
outdoors.





It
is a point
-
to
-
point network and is also called
Ad
hoc
network. A basic peer
-
to
-
peer WLAN
comprises two
computers or/and laptops
equipped with wireless adapter cards within
range of one another

These
networks are easy to
install, manage and require no administration.
There is
no need of central device and each client
would directly access resources of the other client.





It is a Client
-
Server network and is commonly called
Infrastructure network. In these networks, there is

a need of a central device called Access Point. Each
client on the network will communicate with other

clients through this Access Point. It can provide
services to
15
-
50
clients and extends the range of a

peer
-
to
-
peer (ad hoc) network. An Access Point also
connects wired and wireless networks together in a

building. It enables the transfer of data between the
clients of a wireless network and of a wired

network

Wireless transmission via optical carriers opens doors
of opportunity in areas as yet largely unexplored.
Offering significant technical and operational
advantages, optical wireless communication (OWC)
can be, in some applications, a powerful alternative to
and, in others, complementary to existing radio
frequency (RF) wireless systems. Variations of OWC
can be employed in a diverse range of
communication applications ranging from very short
-
range (on the order of
millimetres
) optical
interconnects within integrated circuits through
outdoor inter
-
building links (on the order of
kilometres
) to satellite links (larger than
10
,
000
kilometres
).

Access networks consume a significant portion of overall
Internet energy consumption. With the increase of bit
-
rate
requirements in access networks, future
-
proof access
technologies should be energy efficient. In this paper, we show
how we can build a very high
-
throughput hybrid wireless
-
optical broadband access network (WOBAN). We devise novel
energy
-
saving techniques for WOBAN to improve its energy
efficiency and network utilization. We present a mixed integer
linear program (MILP) model, which acts as a benchmark for
evaluating our techniques. We analyze the impact of energy
-
aware design and protocols on the performance of WOBAN
over dynamic traffic profiles. Illustrative numerical examples
show that, with suitable design parameters, we can efficiently
reduce energy consumption in WOBAN without significantly
impacting the network performance.