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

2. History There have been 5 major milestones in wireless internet communication. 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. The ORIGINAL wireless protocol. –Security implemented via WEP Wired Equivalent Privacy (Legacy) Wired Equivalent Privacy (Legacy) Provided Bandwidth Provided Bandwidth –1 or 2 Mbit/s due to use of CSMA/CA Relatively Unpopular Relatively Unpopular Low interoperability due to loose specifications Low interoperability due to loose specifications Used DSSS Used DSSS Considered Legacy and no longer used Considered Legacy and no longer used

4. 802.11a One of two amendments to the original 802.11 specification released simultaneously One of two amendments to the original 802.11 specification released simultaneously Provided up to 54 Mbit/s bandwidth Provided up to 54 Mbit/s bandwidth Uses OFDM Uses OFDM –Orthogonal Frequency-Division Multiplexing Transmits a signal over several sub signals for higher efficiency Transmits a signal over several sub signals for higher efficiency

5. OFDM

6. 802.11b Second of two amendments released in 1999 Second of two amendments released in 1999 Provided up to 11 Mbit/s bandwidth Provided up to 11 Mbit/s bandwidth Uses DSSS Uses DSSS –Direct-Sequence Spread Spectrum Transmits a signal over several sub signals for higher efficiency Transmits a signal over several sub signals for higher efficiency

7. DSSS

8. 802.11a and b Both introduced at the same time Both introduced at the same time Both use CSMA/CA Both use CSMA/CA 802.11a 802.11a –Faster –More expensive to manufacture –Operated in 5Ghz band –Mainly used in industrial settings 802.11b 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. Pretty much the most common wireless network in use today. Operates on 2.4Ghz band Operates on 2.4Ghz band Provides up 54Mbit/s bandwidth Provides up 54Mbit/s bandwidth –108Mbit/s with special implementations Uses OFDM for modulation Uses OFDM for modulation Adopted quickly after release for cheap and high bandwidth Adopted quickly after release for cheap and high bandwidth

10. 802.11n Newest member of the 802.11 family. Newest member of the 802.11 family. Has rated 600Mbit/s bandwidth Has rated 600Mbit/s bandwidth Introduces MIMO Introduces MIMO –Multiple-Input Multiple-Output OFDM Modulation OFDM Modulation –Uses higher frequencies for increased number of carrier waves

11. 802.11n – New Technologies Beam Forming 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 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 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 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://en.wikipedia.org/wiki/IEEE_802.11 http://en.wikipedia.org/wiki/IEEE_802.11 http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps697 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps697 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps697 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps697 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html http://zone.ni.com/devzone/cda/tut/p/id/4450 http://zone.ni.com/devzone/cda/tut/p/id/4450 http://zone.ni.com/devzone/cda/tut/p/id/4450 http://www.proxim.com/learn/library/whitepapers/maximizing_8021 1g_investment.pdf http://www.proxim.com/learn/library/whitepapers/maximizing_8021 1g_investment.pdf http://www.proxim.com/learn/library/whitepapers/maximizing_8021 1g_investment.pdf http://www.proxim.com/learn/library/whitepapers/maximizing_8021 1g_investment.pdf http://www.proxim.com/learn/library/whitepapers/80211a.pdf http://www.proxim.com/learn/library/whitepapers/80211a.pdf http://www.proxim.com/learn/library/whitepapers/80211a.pdf http://computer.howstuffworks.com/wireless-network1.htm http://computer.howstuffworks.com/wireless-network1.htm http://computer.howstuffworks.com/wireless-network1.htm http://compnetworking.about.com/cs/wireless80211/a/aa80211stan dard.htm http://compnetworking.about.com/cs/wireless80211/a/aa80211stan dard.htm http://compnetworking.about.com/cs/wireless80211/a/aa80211stan dard.htm http://compnetworking.about.com/cs/wireless80211/a/aa80211stan dard.htm http://mobilewireless.wordpress.com/2008/03/01/an-overview-of- ofdm/ http://mobilewireless.wordpress.com/2008/03/01/an-overview-of- ofdm/

16. Questions?