06-07-2012, 09:22 AM
WIRELESS FIDELITY (Wi-Fi)
[attachment=26920]
INTRODUCTION
Most people have heard of Wi-Fi (or WLAN) technology at some
time or other, but not everyone is totally clear on what it is. Wi-Fi is
abbreviated as “Wireless Fidelity”. It is a limited range wireless networking
protocol, based on 802.11 standards. Wi-Fi connectivity allows users, to
transfer digital data without wire, at the speed of broadband.
Wi-Fi is a data transmission system designed to provide location
independent network, access between computing devices by using radio
waves rather than cable infrastructure. It provides users, wireless access to
the services of the corporate network across a building or a campus.
The Institute of Electrical and Electronics Engineers (IEEE) has
ratified 802.11 specifications as a standard for WLANs. This version of
802.11 provides 1 Mbps and 2Mbps data transfer rates. Like all other 802
standards, 802.11 focuses on the bottom two levels of the OSI model,
physical layer and the data link layer. Network users can access LAN almost
from anywhere, without restrictions.
There are 11 channels in Wi-Fi; each channel has a slightly different
frequency. Collision of the network can be avoided by using different
Channels.
Wi-Fi
4
WIRELESS NETWORK
Wireless network is set up by using radio signal frequency to communicate
among computers and other network devices. Sometimes it’s also referred to
as Wi-Fi network or WLAN. Wi-Fi network is getting popular, nowadays,
with ease in its setting.
Both broadband cable as well as DSL modem to access internet,
works with Wireless network. The two main components of Wireless
network are wireless router or access point and the wireless clients. By
attaching a wireless router to a cable/DSL modem, Wireless network start
operating. Wireless clients can be setup by adding wireless card to each
computer and if switch port is available, computers can be connected
directly by cable.
If there is a wired Ethernet network at home, a wireless access point
can be attached to the existing network router to have wireless access at
home.
The IEEE 802.11 standards specify two operating modes:
1) Infrastructure mode: it is used to connect computers with wireless
network adapters (also known as wireless clients), to an existing wired
network with the help of wireless router or access point.
2) Ad hoc mode: it is used to connect wireless clients directly together,
without the need for a wireless router or access point. An ad hoc network
consists of up to 9 wireless clients, which send their data directly to each
other.
In its simplest form, a wireless mesh network is a collection of
wireless devices maintaining RF connectivity to create a seamless path for
data packets to travel.
The Internet router determines a path between the user and the
physical backbone. In the wireless mesh environment, a network can be
envisioned as a collection of access points, routers, or end users (equipped
with wireless receiver/transmitters) that are free to move arbitrarily but
maintain a reliable communication that sends and receive messages.
Each data packet traveling on the Internet backbone has a different
sequential path of nodes even though the source and destination are the
same.
The fundamental structure of a WLAN is the peer-to-peer or peer-tomultipoint
communication between two wireless devices. The purpose is
forming a collection of wireless devices that maintain connectivity with each
other while transferring or routing data in a random manner.
Wi-Fi
5
Wireless network works on two topologies:
1) In peer-to-peer (P-to-P) configuration, each wireless link
replaces a single communication cable and can converse reliably as long as
the two end points are close enough to escape the effects of Radio Frequency
(RF) interference or signal loss
2) A peer-to-multipoint (P-to-Mp) system has one centralized
administrator (or hub) that associates with multiple nodes instead of peer-topeer
collaboration. In general, a reliable connection is dependent upon the
distance between the wireless devices; thus, forming a wireless circle (or
cell) that one must stay within to maintain communication with others.
WLAN can reach a radius of 500 feet indoors and 1000 feet outdoors,
but antennas, transmitters and other access devices can be used to widen that
area. WLANs require a wired access point that plugs all the wireless devices
into the wired network.
Wi-Fi
6
INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERING (IEEE)
Wi-Fi refers to any system that uses the 802.11 standard, which was
developed by the Institute of Electrical and Electronics Engineers (IEEE)
and released in 1997. The term Wi-Fi, which is alternatively spelled WiFi,
Wi-fi, or wifi, was pushed by the Wi-Fi Alliance, a trade group that
pioneered commercialization of the technology.
IEEE is one of the leading standards-making organizations in the
world. IEEE performs its standards making and maintaining functions
through the IEEE Standards Association (IEEE-SA).
One of the more notable IEEE standards is the IEEE 802 LAN/MAN
group of standards which includes the IEEE 802.3 Ethernet standard and the
IEEE 802.11 Wireless Networking standard.
The IEEE standards development process can be broken down into
seven basic steps, as follows:
1) Securing Sponsorship: An IEEE-approved organization must sponsor
a standard. A sponsoring organization is in charge of coordinating and
supervising the standard development from inception to completion. The
professional societies within IEEE serve as the natural sponsor for many
standards.
2) Requesting Project Authorization: To gain authorization for
the standard a Project Authorization Request (PAR) is submitted to the
IEEE-SA Standards Board. The New Standards Committee (NesCom) of the
IEEE-SA Standards Board reviews the PAR and makes a recommendation
to the Standards Board about whether to approve the PAR.
3) Assembling a Working Group: After the PAR is approved, a
"working group" of individuals affected by, or interested in, the standard is
organized to develop the standard. IEEE-SA rules ensure that all Working
Group meetings are open and that anyone has the right to attend and
contribute to the meetings
4) Drafting the Standard: The Working Group prepares a draft of the
proposed standard. Generally, the draft follows the IEEE Standards Style
Manual that sets “guidelines” for the clauses and format of the standards
document.
Wi-Fi
7
5) Balloting: Once a draft of the standard is finalized in the Working
Group, the draft is submitted for Balloting approval. The IEEE Standards
Department sends an invitation-to-ballot to any individual who has
expressed an interest in the subject matter of the standard.
Anyone who responds positively to the invitation-to-ballot becomes a
member of the balloting group, as long as the individual is an IEEE member
or has paid a balloting fee. The IEEE requires that a proposed draft of the
standard receive a response rate of 75% (i.e., at least 75% of potential ballots
are returned) and that, of the responding ballots, at least 75% approve the
proposed draft of the standard. If the standard is not approved, the process
returns to the drafting of the standard step in order to modify the standard
document to gain approval of the balloting group.
6) Review Committee: After getting 75% approval, the draft standard,
along with the balloting comments, are submitted to the IEEE-SA Standards
Board Review Committee (RevCom). The RevCom reviews the proposed
draft of the standard against the IEEE-SA Standards Board Bylaws and the
stipulations set forth in the IEEE-SA Standards Board Operations Manual.
The RevCom then makes a recommendation about whether to approve the
submitted draft of the standard document.
7) Final Vote: Each member of the IEEE-SA Standards Board places a
final vote on the submitted standard document. It takes a majority vote of the
Standards Board to gain final approval of the standard. In general, if the
RevCom recommends approval, the Standards Board will vote to approve
the standard.
Wi-Fi
8
IEEE 802.11 STANDARDS (WIRELESS LAN)
IEEE 802.11 is a set of standards for wireless local area network
(WLAN) computer communication, developed by the IEEE LAN/MAN
Standards Committee (IEEE 802) in the 5 GHz and 2.4 GHz public spectrum
bands.
Although the terms 802.11 and Wi-Fi are often used interchangeably,
the Wi-Fi Alliance uses the term "Wi-Fi" to define a slightly different set of
overlapping standards. In some cases, market demand has led the Wi-Fi
Alliance to begin certifying products before amendments to the 802.11
standard are complete.
The 802.11 family includes over-the-air modulation techniques that
use the same basic protocol. The most popular are those defined by the
802.11b and 802.11g protocols, and are amendments to the original
standard. 802.11a was the first wireless networking standard, but 802.11b
was the first widely accepted one, followed by 802.11g and 802.11n.
IEEE 802.11 (legacy mode):The original version of the standard IEEE
802.11, released in 1997 and clarified in 1999, specified two raw data rates
of 1 and 2 megabits per second (Mbit/s) to be transmitted in Industrial
Scientific Medical frequency band at 2.4 GHz.
Legacy 802.11 was rapidly supplemented (and popularized) by 802.11b.
IEEE 802.11a: The 802.11a standard uses the same core protocol as the
original standard, operates in 5 GHz band with a maximum raw data rate of
54 Mbit/s, which yields realistic net achievable throughput in the mid-20
Mbit/s. Since the 2.4 GHz band is heavily used to the point of being
crowded, using the relatively un-used 5 GHz band gives 802.11a a
significant advantage. However, this high carrier frequency also brings a
slight disadvantage: The effective overall range of 802.11a is slightly less
than that of 802.11b/g; 802.11a signals cannot penetrate as far as those for
802.11b because they are absorbed more readily by walls and other solid
objects in their path.
Wi-Fi
9
IEEE 802.11b:802.11b has a maximum raw data rate of 11 Mbit/s and uses
the same media access method defined in the original standard. 802.11b
products appeared on the market in early 2000, since 802.11b is a direct
extension of the modulation technique defined in the original standard. The
dramatic increase in throughput of 802.11b (compared to the original
standard) along with simultaneous substantial price reductions led to the
rapid acceptance of 802.11b as the definitive wireless LAN technology.
802.11b devices suffer interference from other products operating in the 2.4
GHz band. Devices operating in the 2.4 GHz range include: microwave
ovens, Bluetooth devices, baby monitors and cordless telephones.
IEEE 802.11g: This works in the 2.4 GHz band (like 802.11b) but operates
at a maximum raw data rate of 54 Mbit/s, or about 19 Mbit/s net
throughputs. 802.11g hardware is fully backwards compatible with 802.11b
hardware.
The then-proposed 802.11g standard was rapidly adopted by consumers
starting in January 2003, well before ratification, due to the desire for higher
speeds, and reductions in manufacturing costs. By summer 2003, most dualband
802.11a/b products became dual-band/tri-mode, supporting a and b/g in
a single mobile adapter card or access point. Details of making b and g work
well together occupied much of the lingering technical process; in an
802.11g network, however, activity by a 802.11b participant will reduce the
speed of the overall 802.11g network.
Like 802.11b, 802.11g devices suffer interference from other products
operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range
include: microwave ovens, Bluetooth devices, baby monitors and cordless
telephones.
IEEE 802.11n: 802.11n is a proposed amendment which improves upon the
previous 802.11 standards by adding multiple-input multiple-output
(MIMO) and many other newer features. Though there are already many
products on the market based on Draft 2.0 of this proposal, the TGn
workgroup is not expected to finalize the amendment until November 2008
[attachment=26920]
INTRODUCTION
Most people have heard of Wi-Fi (or WLAN) technology at some
time or other, but not everyone is totally clear on what it is. Wi-Fi is
abbreviated as “Wireless Fidelity”. It is a limited range wireless networking
protocol, based on 802.11 standards. Wi-Fi connectivity allows users, to
transfer digital data without wire, at the speed of broadband.
Wi-Fi is a data transmission system designed to provide location
independent network, access between computing devices by using radio
waves rather than cable infrastructure. It provides users, wireless access to
the services of the corporate network across a building or a campus.
The Institute of Electrical and Electronics Engineers (IEEE) has
ratified 802.11 specifications as a standard for WLANs. This version of
802.11 provides 1 Mbps and 2Mbps data transfer rates. Like all other 802
standards, 802.11 focuses on the bottom two levels of the OSI model,
physical layer and the data link layer. Network users can access LAN almost
from anywhere, without restrictions.
There are 11 channels in Wi-Fi; each channel has a slightly different
frequency. Collision of the network can be avoided by using different
Channels.
Wi-Fi
4
WIRELESS NETWORK
Wireless network is set up by using radio signal frequency to communicate
among computers and other network devices. Sometimes it’s also referred to
as Wi-Fi network or WLAN. Wi-Fi network is getting popular, nowadays,
with ease in its setting.
Both broadband cable as well as DSL modem to access internet,
works with Wireless network. The two main components of Wireless
network are wireless router or access point and the wireless clients. By
attaching a wireless router to a cable/DSL modem, Wireless network start
operating. Wireless clients can be setup by adding wireless card to each
computer and if switch port is available, computers can be connected
directly by cable.
If there is a wired Ethernet network at home, a wireless access point
can be attached to the existing network router to have wireless access at
home.
The IEEE 802.11 standards specify two operating modes:
1) Infrastructure mode: it is used to connect computers with wireless
network adapters (also known as wireless clients), to an existing wired
network with the help of wireless router or access point.
2) Ad hoc mode: it is used to connect wireless clients directly together,
without the need for a wireless router or access point. An ad hoc network
consists of up to 9 wireless clients, which send their data directly to each
other.
In its simplest form, a wireless mesh network is a collection of
wireless devices maintaining RF connectivity to create a seamless path for
data packets to travel.
The Internet router determines a path between the user and the
physical backbone. In the wireless mesh environment, a network can be
envisioned as a collection of access points, routers, or end users (equipped
with wireless receiver/transmitters) that are free to move arbitrarily but
maintain a reliable communication that sends and receive messages.
Each data packet traveling on the Internet backbone has a different
sequential path of nodes even though the source and destination are the
same.
The fundamental structure of a WLAN is the peer-to-peer or peer-tomultipoint
communication between two wireless devices. The purpose is
forming a collection of wireless devices that maintain connectivity with each
other while transferring or routing data in a random manner.
Wi-Fi
5
Wireless network works on two topologies:
1) In peer-to-peer (P-to-P) configuration, each wireless link
replaces a single communication cable and can converse reliably as long as
the two end points are close enough to escape the effects of Radio Frequency
(RF) interference or signal loss
2) A peer-to-multipoint (P-to-Mp) system has one centralized
administrator (or hub) that associates with multiple nodes instead of peer-topeer
collaboration. In general, a reliable connection is dependent upon the
distance between the wireless devices; thus, forming a wireless circle (or
cell) that one must stay within to maintain communication with others.
WLAN can reach a radius of 500 feet indoors and 1000 feet outdoors,
but antennas, transmitters and other access devices can be used to widen that
area. WLANs require a wired access point that plugs all the wireless devices
into the wired network.
Wi-Fi
6
INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERING (IEEE)
Wi-Fi refers to any system that uses the 802.11 standard, which was
developed by the Institute of Electrical and Electronics Engineers (IEEE)
and released in 1997. The term Wi-Fi, which is alternatively spelled WiFi,
Wi-fi, or wifi, was pushed by the Wi-Fi Alliance, a trade group that
pioneered commercialization of the technology.
IEEE is one of the leading standards-making organizations in the
world. IEEE performs its standards making and maintaining functions
through the IEEE Standards Association (IEEE-SA).
One of the more notable IEEE standards is the IEEE 802 LAN/MAN
group of standards which includes the IEEE 802.3 Ethernet standard and the
IEEE 802.11 Wireless Networking standard.
The IEEE standards development process can be broken down into
seven basic steps, as follows:
1) Securing Sponsorship: An IEEE-approved organization must sponsor
a standard. A sponsoring organization is in charge of coordinating and
supervising the standard development from inception to completion. The
professional societies within IEEE serve as the natural sponsor for many
standards.
2) Requesting Project Authorization: To gain authorization for
the standard a Project Authorization Request (PAR) is submitted to the
IEEE-SA Standards Board. The New Standards Committee (NesCom) of the
IEEE-SA Standards Board reviews the PAR and makes a recommendation
to the Standards Board about whether to approve the PAR.
3) Assembling a Working Group: After the PAR is approved, a
"working group" of individuals affected by, or interested in, the standard is
organized to develop the standard. IEEE-SA rules ensure that all Working
Group meetings are open and that anyone has the right to attend and
contribute to the meetings
4) Drafting the Standard: The Working Group prepares a draft of the
proposed standard. Generally, the draft follows the IEEE Standards Style
Manual that sets “guidelines” for the clauses and format of the standards
document.
Wi-Fi
7
5) Balloting: Once a draft of the standard is finalized in the Working
Group, the draft is submitted for Balloting approval. The IEEE Standards
Department sends an invitation-to-ballot to any individual who has
expressed an interest in the subject matter of the standard.
Anyone who responds positively to the invitation-to-ballot becomes a
member of the balloting group, as long as the individual is an IEEE member
or has paid a balloting fee. The IEEE requires that a proposed draft of the
standard receive a response rate of 75% (i.e., at least 75% of potential ballots
are returned) and that, of the responding ballots, at least 75% approve the
proposed draft of the standard. If the standard is not approved, the process
returns to the drafting of the standard step in order to modify the standard
document to gain approval of the balloting group.
6) Review Committee: After getting 75% approval, the draft standard,
along with the balloting comments, are submitted to the IEEE-SA Standards
Board Review Committee (RevCom). The RevCom reviews the proposed
draft of the standard against the IEEE-SA Standards Board Bylaws and the
stipulations set forth in the IEEE-SA Standards Board Operations Manual.
The RevCom then makes a recommendation about whether to approve the
submitted draft of the standard document.
7) Final Vote: Each member of the IEEE-SA Standards Board places a
final vote on the submitted standard document. It takes a majority vote of the
Standards Board to gain final approval of the standard. In general, if the
RevCom recommends approval, the Standards Board will vote to approve
the standard.
Wi-Fi
8
IEEE 802.11 STANDARDS (WIRELESS LAN)
IEEE 802.11 is a set of standards for wireless local area network
(WLAN) computer communication, developed by the IEEE LAN/MAN
Standards Committee (IEEE 802) in the 5 GHz and 2.4 GHz public spectrum
bands.
Although the terms 802.11 and Wi-Fi are often used interchangeably,
the Wi-Fi Alliance uses the term "Wi-Fi" to define a slightly different set of
overlapping standards. In some cases, market demand has led the Wi-Fi
Alliance to begin certifying products before amendments to the 802.11
standard are complete.
The 802.11 family includes over-the-air modulation techniques that
use the same basic protocol. The most popular are those defined by the
802.11b and 802.11g protocols, and are amendments to the original
standard. 802.11a was the first wireless networking standard, but 802.11b
was the first widely accepted one, followed by 802.11g and 802.11n.
IEEE 802.11 (legacy mode):The original version of the standard IEEE
802.11, released in 1997 and clarified in 1999, specified two raw data rates
of 1 and 2 megabits per second (Mbit/s) to be transmitted in Industrial
Scientific Medical frequency band at 2.4 GHz.
Legacy 802.11 was rapidly supplemented (and popularized) by 802.11b.
IEEE 802.11a: The 802.11a standard uses the same core protocol as the
original standard, operates in 5 GHz band with a maximum raw data rate of
54 Mbit/s, which yields realistic net achievable throughput in the mid-20
Mbit/s. Since the 2.4 GHz band is heavily used to the point of being
crowded, using the relatively un-used 5 GHz band gives 802.11a a
significant advantage. However, this high carrier frequency also brings a
slight disadvantage: The effective overall range of 802.11a is slightly less
than that of 802.11b/g; 802.11a signals cannot penetrate as far as those for
802.11b because they are absorbed more readily by walls and other solid
objects in their path.
Wi-Fi
9
IEEE 802.11b:802.11b has a maximum raw data rate of 11 Mbit/s and uses
the same media access method defined in the original standard. 802.11b
products appeared on the market in early 2000, since 802.11b is a direct
extension of the modulation technique defined in the original standard. The
dramatic increase in throughput of 802.11b (compared to the original
standard) along with simultaneous substantial price reductions led to the
rapid acceptance of 802.11b as the definitive wireless LAN technology.
802.11b devices suffer interference from other products operating in the 2.4
GHz band. Devices operating in the 2.4 GHz range include: microwave
ovens, Bluetooth devices, baby monitors and cordless telephones.
IEEE 802.11g: This works in the 2.4 GHz band (like 802.11b) but operates
at a maximum raw data rate of 54 Mbit/s, or about 19 Mbit/s net
throughputs. 802.11g hardware is fully backwards compatible with 802.11b
hardware.
The then-proposed 802.11g standard was rapidly adopted by consumers
starting in January 2003, well before ratification, due to the desire for higher
speeds, and reductions in manufacturing costs. By summer 2003, most dualband
802.11a/b products became dual-band/tri-mode, supporting a and b/g in
a single mobile adapter card or access point. Details of making b and g work
well together occupied much of the lingering technical process; in an
802.11g network, however, activity by a 802.11b participant will reduce the
speed of the overall 802.11g network.
Like 802.11b, 802.11g devices suffer interference from other products
operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range
include: microwave ovens, Bluetooth devices, baby monitors and cordless
telephones.
IEEE 802.11n: 802.11n is a proposed amendment which improves upon the
previous 802.11 standards by adding multiple-input multiple-output
(MIMO) and many other newer features. Though there are already many
products on the market based on Draft 2.0 of this proposal, the TGn
workgroup is not expected to finalize the amendment until November 2008