Overview of the 802.11 WLAN Protocols

802.11

• 802.11 uses Barker 11 coding
• For modulation, 802.11 uses differential binary phase-shift keying (DBPSK) 
• Speed : 1, 2 Mpbs

802.11b

• 802.11b uses differential quadrature phase-shift keying (DQPSK)
• 802.11b uses complementary code keying (CCK) for coding. 
• Frequency Range : 2.4Ghz
• Band width : 22 Mhz
• Stream data rate : 1, 2, 5.5, 11
• Modulation : DSSS
• Indoor range : 35 meters
• Outdoor range : 140 meters
• Non-Overlapping Channel 1,6,11
• MIMO : N/A

802.11g

• Frequency Range : 2.4Ghz
• Band width : 20 Mhz
• Stream data rate : 6, 9, 12, 18, 24, 36, 48, 54
• Modulation : OFDM
• Indoor range : 38 meters
• Outdoor range : 140 meters
• Compatible with 802.11b, using the same modulation and coding as 802.11b for the 1, 2, 5.5, and 11-Mbps rates for Higher Data OFDM.
• MIMO : N/A

802.11a

• Frequency Range : 5Ghz
• Band width : 20 Mhz
• Stream data rate : 6, 9, 12, 18, 24, 36, 48, 54
• Modulation : OFDM
• Indoor range : 35 meters
• Outdoor range : 120 meters
• In-compatible with 802.11, 802.11b, and 802.11g,
• MIMO : N/A

802.11n

• Frequency Range : 2.4/5Ghz
• Band width : 20/40 Mhz
• Maximum Speed for 20 Mhz: upto 65Mbit/s 
• Maximum Speed for 40 Mhz: upto 135Mbit/s 
• Modulation : OFDM
• Indoor range : 70 meters
• Outdoor range : 250 meters
• Backward compatible with 802.11b/g and a    
• Different antennas to send and receive, thus increasing throughput and accomplishing more of a full duplex operation.
• For the allocated time to send frames, only CTS to self is used with 802.11
• Another feature of 802.11n that makes it much more efficient is the way it uses block acknowledgments as opposed to acknowledging each unicast packet like the other 802.11 protocols do. A block acknowledgment works by sending a number of frames before having them acknowledged. This is similar to the way TCP works.
• RIFS (Reduced InterFrame Space) used in 802.11n as compare to DIFS (Distributed InterFrame Space)) in 802.11 a,b,g
• MIMO : 4

802.11ac

• Frequency Range : 5Ghz
• Band width : 20/40/80/160 Mhz
• Maximum Speed for 20 Mhz: upto 86.7Mbit/s 
• Maximum Speed for 40 Mhz: upto 180Mbit/s 
• Maximum Speed for 80 Mhz: upto 390Mbit/s 
• Maximum Speed for 160 Mhz: upto 780Mbit/s 
• Modulation : OFDM
• Indoor range : 70 meters
• Outdoor range : 250 meters
• MIMO : 8