WLAN Standard 802.11n
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Revision as of 00:28, 7 April 2009
WLAN Standard 802.11n is the latest version of the 802.11 wireless networking standard with standards 802.11g and 802.11b as predecessors. 802.11n boasts a raw data rate of 600 Mbps; a massive increase from 802.11g's 54 Mbps. To achieve this, 802.11n implements multiple-input multiple-output operation, channel bonding and frame aggregation, among others.
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Techniques
Multiple-Input Multiple-Output (MIMO)
MIMO uses multiple antennas at the transmitter and receiver which provides the ability to use spatial division multiplexing and multipath signals.
Spatial division multiplexing (SDM) spatially multiplexes multiple independent data streams that are transferred within one spectral channel of bandwidth. Each spatial stream requires an antenna at both the receiver and transmitter. As the number of antennas increase the number of spatial data streams increase and, in turn, the amount of throughput. The throughput goes up linearly to the number of antennas added. Two antennas (four total, two at the receiver, two at the transmitter) double throughput, three triple it, four quadruple it. The maximum number of antennas 802.11n supports is four.
Multipath signals are the reflected signals arriving at the receiver some time after the line of sight transmission has been received. In 802.11a/b/g protocol versions these reflected signals were treated as interference and the ability to recover information from the signal was hindered. MIMO uses these reflected signals to increase the ability to recover information that was sent in the signal.
