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802.11a,b,g, and n Wireless

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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802.11a,b,g, and n Wireless

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  1. 802.11a,b,g, and n Wireless By Winway Pang

  2. 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

  3. 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

  4. 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

  5. OFDM

  6. 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

  7. DSSS

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 802.11n – New Technologies • Frame aggregation • Aggregate multiple frames destined for a specific AP and send them together to reduce overhead

  15. 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/

  16. Questions?

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