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

History There have been 5 major milestones in wireless internet communication. There have been 5 major milestones in wireless internet communication. – – 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

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

802.11a One of two amendments to the original specification released simultaneously One of two amendments to the original 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

OFDM

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

DSSS

802.11a and b Both introduced at the same time Both introduced at the same time Both use CSMA/CA Both use CSMA/CA a a –Faster –More expensive to manufacture –Operated in 5Ghz band –Mainly used in industrial settings b b –Slower –Cheaper to manufacture –Operated in 2.4Ghz band. –Mainly used in residential settings

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

802.11n Newest member of the family. Newest member of the 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

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

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

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.

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

References /ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html 3/ps8382/prod_white_paper0900aecd806b8ce7_ns767_Networking_ Solutions_White_Paper.html g_investment.pdf 1g_investment.pdf 1g_investment.pdf 1g_investment.pdf dard.htm dard.htm dard.htm dard.htm ofdm/ ofdm/

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