802.11n: A Technology Snapshot

By Luc Roy, VP Enterprise Mobility, Siemens Communications — September 19, 2008

This primer accompanies the article Eight Keys For A Successful Migration To 802.11n.

802.11n is designed to provide over-the-air transmission speeds of up to 300 Mbps with data throughputs of 150 Mbps. Indoor range is up to 500 feet (150 meters) and 1,300 feet (400 meters), both about twice that of current 802.11a/b/g technologies.

At the heart of the 802.11n enhancements are two new technologies:

  • MIMO (for Multiple Input, Multiple Output) -- On the transmit side, MIMO allows multiple data streams to use the same frequency but over different spatial channels via Spatial Division Multiplexing (SDM). This increases both the transmission power and data that can be sent over air. On the receiving side, MIMO can combine signals from multiple paths to improve reception quality. In 802.11a/b/g devices, multipath signals are considered channel interference, while 802.11n turns that into an advantage by using it as a way to recover message information from the signal.
  • Channel Bonding -- 802.11n can double the channel width compared to 802.11a/g technologies, from 20 MHz to 40 MHz using a channel bonding mechanism that results in a doubling of data rate capability.
In addition, 802.11n supports both 2.4 GHz transmissions with 802.11b/g backward compatibility that can be turned on and off, as well as 5 GHz transmissions with 802.11a backward compatibility which can also be turned on and off.

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