Transcript Document 7443852

IEEE 802.11
Standards
IEEE 802.11 Standards
• First published in June 1997.
• Defines technologies at the Physical layer and the MAC
sublayer of the Data-Link layer.
• The standard does not address the upper layers of the
OSI model.
• The PHY Task Group has developed three Physical layer
specifications.
IEEE 802.11 Standard
PHY Tack Group
• Infrared (IR): Uses a light-based medium. This was the
first medium standard. By the time it was implemented,
it was rendered obsolete.
• Frequency Hopping Spread Spectrum (FHSS): Defined
as narrowband signals or as spread spectrum signals. An
RF signal is considered spread spectrum when the
bandwidth of a signal is more than what is required for
carrying data.
• Direct sequence spread spectrum (DSSS): Spread
spectrum technology--easy to use and to implement.
continued...
• In 802.11 Prime, the frequency space of both FHSS or
DSSS radio cards can be transmitted on is the
Industrial, Scientific, and Medical (ISM) band.
• DSSS cards can transmit in channels that are subdivided
from the 2.4 to 2.4835 GHz ISM band.
• FHSS can transmit at a 1 MHz subcarrier in the 2.402 to
2.480 GHz range of the ISM band.
• FHSS and DSSS cannot communicate with each other.
Ratified Amendments
ratify
approve and express assent,
responsibility, or obligation;
"All parties ratified the
peace treaty"
802.11b
+ Achieved data rates up to 11
Mbps
- Uses the same 2.4 GHz band
as bluetooth, microwave etc...
802.11a
+ Operates in 5 GHz band, with a
maximum raw data rate of 54 Mbit/s
- Signals more readily absorbed by
walls, but less interference from
other devices
802.11g
+ High data rates and
backwards compatible
+ Triggered huge sales of WiFi gear in homes, offices and
enterprise levels
Wireless G Access Point
802.11d
+ Allowed 802.11 to operate in
areas not served by original
standard
+ Defined info specific for
Frequency Hopping access
points country to country
802.11F
+ Mandated vendor access
points to support roaming,
access point hopping
- Failed to dictate how roaming
should actally transpire
802.11h
+ Defined mechanisms for DFS and
TPC for operation in the 5 GHz
band in Europe
+ Some Vendors have applied TPC
and DFS - like services to radios
cards operating on 2.4 GHz ISM
band
Tesla's Oscillator
802.11i
+ Updated security from WEP to
CCMP/AES and defined TKIP
+ Required the use of an EAP,
Extensible Authentication
Protocol
+ Defined method of establishing
authentication. (RSN)
802.11j
+ Main goal was to obtain
Japanese regulatory approval by
enhancing 802.11 to operate in
Japanese 4.9 and 5 GHz bands
+ "Tight" with the Japanese
802.11e
+ Defines the layer 2 MAC methods to
meet QoS requirements for timesensitive applications over wireless
LANs.
- Original standard defined DCF and
PCF, which were not adequate for
voice, audio, and video traffic
Quality Control
Draft Amendments
The 802.11 standard has been updated many times since
the standard’s induction in 1997. The most popular changes
to the standard are the 802.11a, 802.11g, and 802.11b
amendments.
With the release of 802.11a it allowed speeds up to
54Mbps placed in the 5 GHz range. The 802.11b amendment
allowed for speeds up to 11 Mbps in the 2.4 GHz range. The
‘b’ was not compatible with the ‘a’ amendment because it
operated at a different frequency, but it did allow the
range to be increased to 300 feet.
The 802.11g amendment was designed to over take the
802.11b amendment, allowed for speeds up to 54 Mbps in
the 2.4 GHz range with enhanced security, and less
overlapping channels. Each major amendment gets a new
letter; IEEE is currently in the process of working on
amendment ‘n’ of the 802.11 standard.
The new amendment offers a lot of changes from previous
ones. The speeds of the data transfer will be almost twice
the speed as previous versions. With theoretical speeds
ranging up to 540 Mbps.
There are some very interesting things happening in the
planning of the new amendment. To help with the creation
of the amendment, IEEE created the Enhanced Wireless
Consortium (EWC), to maintain and implement the rest of
the amendments that the company was going to put forth.
It is the task force’s job to implement new technology,
while upholding to previous versions of 802.11.
The CPU manufacturer, Intel, is also currently a having a
considerable amount of control in the creation of the
amendment, pushing the amendment to go farther than
previous expectations. (Wilson) Intel is pushing for faster
speeds, and better reliability, and the use of MIMO
technology. Intel was the producer of many of the technical
documents used for the current drafts of the amendment.
It is partly Intel’s fault that the amendment is taking so
long to be released. Their goal is to test the new standard
of 100 Mbps in the 2.4 GHz frequency range under many
circumstances, ranging from home to public environments.