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:
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.
- 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