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802.11a,b,g, and n Wireless By Winway Pang History There have been 5 major milestones in wireless internet communication. 802.11 – Released in 1997, the original wireless protocol 802.11a – Released in late 1999 802.11b – Released in late 1999 802.11g – Released in mid 2003

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history
History
  • There have been 5 major milestones in wireless internet communication.
    • 802.11 – Released in 1997, the original wireless protocol
    • 802.11a – Released in late 1999
    • 802.11b – Released in late 1999
    • 802.11g – Released in mid 2003
    • 802.11n – Released in 2009
802 11 1997
802.11-1997
  • The ORIGINAL wireless protocol.
    • Security implemented via WEP
      • Wired Equivalent Privacy (Legacy)
  • Provided Bandwidth
    • 1 or 2 Mbit/s due to use of CSMA/CA
  • Relatively Unpopular
  • Low interoperability due to loose specifications
  • Used DSSS
  • Considered Legacy and no longer used
802 11a
802.11a
  • One of two amendments to the original 802.11 specification released simultaneously
  • Provided up to 54 Mbit/s bandwidth
  • Uses OFDM
    • Orthogonal Frequency-Division Multiplexing
      • Transmits a signal over several sub signals for higher efficiency
802 11b
802.11b
  • Second of two amendments released in 1999
  • Provided up to 11 Mbit/s bandwidth
  • Uses DSSS
    • Direct-Sequence Spread Spectrum
      • Transmits a signal over several sub signals for higher efficiency
802 11a and b
802.11a and b
  • Both introduced at the same time
  • Both use CSMA/CA
  • 802.11a
    • Faster
    • More expensive to manufacture
    • Operated in 5Ghz band
    • Mainly used in industrial settings
  • 802.11b
    • Slower
    • Cheaper to manufacture
    • Operated in 2.4Ghz band.
    • Mainly used in residential settings
802 11g
802.11g
  • Pretty much the most common wireless network in use today.
  • Operates on 2.4Ghz band
  • Provides up 54Mbit/s bandwidth
    • 108Mbit/s with special implementations
  • Uses OFDM for modulation
  • Adopted quickly after release for cheap and high bandwidth
802 11n
802.11n
  • Newest member of the 802.11 family.
  • Has rated 600Mbit/s bandwidth
  • Introduces MIMO
    • Multiple-Input Multiple-Output
  • OFDM Modulation
    • Uses higher frequencies for increased number of carrier waves
802 11n new technologies
802.11n – New Technologies
  • Beam Forming
    • Takes advantage of multi-antenna setup
    • Makes signals from separate antenna arrive in sync
    • Out of sync leads to interference
    • In sync leads to greater signal strength
802 11n new technologies12
802.11n – New Technologies
  • Multipath/Spatial Diversity
    • Multiple antenna/radios send/receive signals
    • Different signals reach receivers at different times
    • Use math to combine signals for greater quality
    • Each stream can carry separate data
802 11n new technologies13
802.11n – New Technologies
  • Guard interval reduction
    • Guard interval is a time of radio silence
    • Used to avoid interference
    • 802.11n can reduce guard interval from 800us to 400us.
802 11n new technologies14
802.11n – New Technologies
  • Frame aggregation
    • Aggregate multiple frames destined for a specific AP and send them together to reduce overhead
references
References
  • http://en.wikipedia.org/wiki/IEEE_802.11
  • http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps6973/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_Solutions_White_Paper.html
  • http://zone.ni.com/devzone/cda/tut/p/id/4450
  • http://www.proxim.com/learn/library/whitepapers/maximizing_80211g_investment.pdf
  • http://www.proxim.com/learn/library/whitepapers/80211a.pdf
  • http://computer.howstuffworks.com/wireless-network1.htm
  • http://compnetworking.about.com/cs/wireless80211/a/aa80211standard.htm
  • http://mobilewireless.wordpress.com/2008/03/01/an-overview-of-ofdm/