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Wireless Standards - 802.11a 802.11b 802.11g 802.11n 802.11i Explained

The IEEE 802.11 family of standards which provides for Wireless Ethernet or (Wi-Fi) has evolved over the years. This article explains the differences between 802.11a 802.11b 802.11g 802.11n and 802.11i.


The IEEE (Institute of Electrical and Electronics Engineers) released the first wireless specification, 802.11, in 1997. Unfortunately, with a maximum network bandwidth of only 2 Mbps, it was impractical for most purposes and very little 802.11 product was ever manufactured.


In 1999 IEEE released the 802.11a amendment to the original standard. 802.11a uses the same core protocol as the original standard, but operates in 5 GHz band, and uses a frequency-division multiplexing scheme that produces a maximum data rate of 54 Mbps. However, at the about same time 802.11a was created, the 802.11b specification was in development, and 802.11b signals are not absorbed as easily by walls and other solid objects in their path.


Later in 1999 released the 802.11b specification which operates in the 2.4 GHz band and produces a maximum data rate of 11 Mbps. 2.4 GHz devices are much cheaper to produce and the signals can penetrate walls and solid objects better than 802.11a, so 802.11b gained popularity much faster than did 802.11a. However, because of it's higher bandwidth, 802.11a can be found in many business networks.

Because 802.11a and 802.11b use different frequencies, the two devices are incompatible with each other. Some manufacturers produce devices that are compatible with both frequencies, but they actually have circuits for both frequencies on the devices.


In 2003 the 802.11g standard was released. It uses both the 2.4 GHz and 5 GHz band, uses the same frequency-division multiplexing scheme as 802.11a, and produces a maximum data rate of 54 Mbps. It has built-in backward compatibility with 802.11b and can achieve the speed of 802.11a. Because of its higher speed the 802.11g standard is quickly gaining popularity.


In 2009 the 802.11n standard was released. It improves the previous standards by adding multiple-input multiple-output (MIMO) technology. MIMO uses multiple antennas to coherently resolve more information than possible using a single antenna. It uses a multiplexing scheme called Spatial Division Multiplexing (SDM). SDM multiplexes multiple independent 40 MHz data streams. A maximum data rate 600 Mbps is achieved by multiplexing four 40 MHz streams.


The security protocol used for all the 802.11 standards, Wired Equivalent Privacy (WEP), was shown to have severe security weaknesses. The Wi-Fi Alliance has created the 802.11i specification to incorporate a more robust security scheme called Wi-Fi Protected Access (WPA) which uses Advanced Encryption Standard (AES) block cipher.

More Networking Protocols and Standards:
• OSI Transport Layer
• Video - Data Link Layer of OSI Networking Model
• IGRP (Interior Gateway Routing Protocol)
• Video - Introducing the OSI Model
• SYN-ACK Handshake to Establish a TCP Connection
• Wireless Standards - 802.11a 802.11b 802.11g 802.11n 802.11i Explained
• IPv6 Address Format
• Virtual Local Area Networks (VLANs)
• Major Protocols in the TCP/IP Suite
• IPv4 Address Classes

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