WI-FI-WIRELESS FIDELITY
Wireless
Fidelity is commonly known as Wi-Fi, developed on IEEE 802.11 standards, is commonly used technology development in wireless
communication. As the names indicate, WI-FI provides wireless access to
applications and data across a radio network. WI-FI sets up many ways to build
up a connection between the transmitter and the receiver such as DSSS, FHSS,
IRInfrared and OFDM.
Wi-Fi
provide its users with the authorization of connecting to the Internet from any
place such as their home, office or a public place without the hassles of
plugging in the wires. Wi-Fi is faster than the conventional modem for
accessing information over a huge network. With the help of different
amplifiers, the users can easily alter their location without interference in
their network access. Wi-Fi devices are yielding with each other to grant
well-organized access of information to the user. Wi-Fi location, the users can
attach to the wireless network is called a Wi-Fi hotspot. Through the Wi-Fi
hotspot, the user can evenimprove their home business as accessing information
through Wi-Fi is easy Accessing a wireless network through a hotspot in some
cases is free of cost while in some it may carry extra charges. Many set of
Wi-Fi devices such as PCI, miniPCI, USB, Cardbus and PC card, ExpressCard make
the Wi-Fi experience suitable and enjoyable for the users. Distance from a
wireless network can decrease the signal strength to quite an extent; some
devices such as Ermanno Pietrosemoli and EsLaRed of Venezuela Distance are used
for amplifying the signal power of the network. These devices create embedded
systems that communicate with any other node on the Internet.
Wi-Fi
uses radio networks to broadcast data between its nodes. Such networks are made
up of cells that grant coverage across the network. The further the number of
cells, the larger and stronger is the coverage on the radio network. The radio
technology is a absolute package deal as it offers a secure and reliable
connectivity. Radio bands such as 2.4GHz and 5GHz depend on wireless hardware
such Ethernet protocol and CSMA. Originally, Phase Shift Keying (PSK), a
modulation method for transmission of data was used, but now it has been
replaced with CCK. Wi-Fi uses many spectrum such as FHSS and DSSS. The most accepted
Wi-Fi technology such as 802.11b operates on the range of 2.40 GHz up to 2.4835
GHz band. This provides a complete platform for operating Bluetooth strategy,
cellular phones, and other scientific equipments. While 802.11a technology has
the range of 5.725 GHz to 5.850 GHz and provides up to 54 Mbps in speed.
802.11g technology is even enhanced as it cover three non-overlapping channels
and permit PBCC. 802.11e technology takes a pale lead by providing outstanding
streaming quality of video, audio, voice channels etc.
Wi-Fi
communication devices are extended forms of radios used for cell phones and
walkie-talkies: they simultaneously transmit and receive radio waves and
convert 1s to 0s into the radio waves along with reconverting the radio waves
into 1s and 0s, however the Wi-Fi radios enjoy some exceptional features.
Advantages
Wi-Fi
allows cheaper deployment of local area networks (LANs). Also spaces where
cables cannot be run, such as outdoor areas and historical buildings, can host wireless
LANs.
Manufacturers
are building wireless network adapters into most laptops. The price of chipsets
for Wi -Fi continues to drop, making it an economical networking option
included in even more devices.
Different
competitive brands of access points and client network-interfaces can
inter-operate at a basic level of service. Products designated as "Wi-Fi
Certified" by the Wi-Fi Alliance are backwards compatible. Unlike mobile
phones, any standard Wi-Fi device will work anywhere in the world.
Wi-Fi
Protected Access encryption (WPA2) is considered secure, provided a strong
passphrase is used. New protocols for quality-of-service (WMM) make Wi-Fi more
suitable for latency-sensitive applications (such as voice and video). Power
saving mechanisms (WMM Power Save) extend battery life.
Limitations
Spectrum
assignments and operational limitations are not consistent worldwide: most of
Europe allows for an additional two channels beyond those permitted in the US
for the 2.4 GHz band (1–13 vs. 1–11), while Japan has one more on top of that
(1–14). As of 2007, Europe is essentially homogeneous in this respect.
A Wi-Fi
signal occupies five channels in the 2.4 GHz band. Any two channel numbers that
differ by five or more, such as 2 and 7, do not overlap. The oft-repeated adage
that channels 1, 6, and 11 are the only non-overlapping channels is, therefore,
not accurate. Channels 1, 6, and 11 are the only group of three non-overlapping
channels in the U.S. In Europe and Japan using Channels 1, 5, 9, and 13 for 802.11g
and 802.11n is recommended.
Equivalent
isotropically radiated power (EIRP) in the EU is limited to 20 dBm (100
mW). The current 'fastest' norm,
802.11n, uses double the radio spectrum/bandwidth (40 MHz) compared to 802.11a
or 802.11g (20 MHz). This means there can be only one 802.11n network on the
2.4 GHz band at a given location, without interference to/from other WLAN
traffic. 802.11n can also be set to use 20 MHz bandwidth only to prevent
interference in dense community.
WIFI NETWORK SERVICES:
2. Distribution
and integration
3. Association,
re-association, and disassociation
4. Authentication
and deauthentication
5. Providing
privacy
Distribution:
This
service is used by mobile stations in an infrastructure network every time they
send data. Once a frame has been accepted by an access point, it uses the
distribution service to deliver the frame to its destination. Any communication
that uses an access point travels through the distribution service, including
communications between two mobile stations associated with the same access
point.
Integration:
Integration
is a service provided by the distribution system; it allows the connection of
the distribution system to a non-IEEE 802.11 network. The integration function
is specific to the distribution system used and therefore is not specified by
802.11, except in terms of the services it must offer.
Association:
Delivery
of frames to mobile stations is made possible because mobile stations register,
or associate, with access points. The distribution system can then use the
registration information to determine which access point to use for any mobile
station.
Re-association:
When a
mobile station moves between basic service areas within a single extended
service area, it must evaluate signal strength and perhaps switch the access
point with which it is associated. Reassociations are initiated by mobile
stations when signal conditions indicate that a different association would be
beneficial; they are never initiated by the access point. After the reassociation
is complete, the distribution system updates its location records to reflect
the reachability of the mobile station through a different access point.
Disassociation:
To
terminate an existing association, stations may use the disassociation service.
When stations invoke the disassociation service, any mobility data stored in
the distribution system is removed. Once disassociation is complete, it is as
if the station is no longer attached to the network. Disassociation is a polite
task to do during the station shutdown process. The MAC is, however, designed
to accommodate stations that leave the network without formally disassociating.
Authentication/deauthentication:
Physical
security is a major component of a wired LAN security solution.
Wired
network‘s equipment can be locked inside offices. Wireless networks cannot
offer the same level of physical security, however, and therefore must depend
on additional authentication routines to ensure that users accessing the
network are authorized to do so. Authentication is a necessary prerequisite to
association because only authenticated users are authorized to use the network.
(In practice, though, many access points are configured for
"open-system" mode and will authenticate any station.)
Deauthentication
terminates an authenticated relationship. Because authentication is needed
before network use is authorized, a side effect of deauthentication is
termination of any current association.
WIFI SECURITY
WiFi
hotspots can be open or secure. If a hotspot is open, then anyone with a WiFi
card can access the hotspot. If it is secure, then the user needs to know a WEP
key to connect. WEP stands for Wired Equivalent Privacy. WEP is an encryption
system for the data that 802.11 sends through the air. Encryption system
prevents any non-authorized party from reading or changing data. Specifically,
it is the process of encoding bit stream in such a way that only the person (or
computer) with the key (a digital sequence) can decode it.
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