Cisco Cisco Aironet 1140 Access Point 디자인 가이드
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Cisco 1140 Series Access Point Deployment Guide
OL-18384-01
So, What Exactly Is 11n?
MIMO
Multiple Input, Multiple Output, or MIMO, is at the heart of 802.11n and provides for a given
transmission to operate at much higher data rates than the PHY would otherwise be capable.
transmission to operate at much higher data rates than the PHY would otherwise be capable.
Spatial Division Multiplexing (SDM) is the ability of an 11n access point to use multiple radios and
antennas to transmit different signals to the same recipient. The receiver puts the multiple discrete
signals back together, thereby realizing a higher data rate than would otherwise be achieved by a single
transmitting radio. In ideal conditions, utilizing Spatial Multiplexing permits 802.11n to nearly double
throughput when multiple spatial streams are utilized.
antennas to transmit different signals to the same recipient. The receiver puts the multiple discrete
signals back together, thereby realizing a higher data rate than would otherwise be achieved by a single
transmitting radio. In ideal conditions, utilizing Spatial Multiplexing permits 802.11n to nearly double
throughput when multiple spatial streams are utilized.
In addition to Spatial Division Multiplexing, MIMO also supports Maximal Ratio Combining (MRC)
which allows multiple receive signals from discrete antennas to be combined. Traditional methods of
receive diversity, as implemented in 802.11a/g devices, only switched to the antenna with the strongest
signal thus disregarding information available on the other antenna. In sharp contrast, by using multiple
antennas and advanced digital signal processing, 802.11n devices can decrypt both the original RF
transmission and subsequent reflected copies to form a more reliable ‘super’ signal comprised of
information gained from all antennas. Put more clearly, a hypothetical person with three ears will hear
more information than a person with two. The same goes for Access Points and their respective number
of antennas. By having multiple RF ‘viewpoints’ an 802.11n device enjoys increased reliability in
comparison to a legacy device meaning packets will reach their destination on the first transmission
reducing time wasted via costly retries.
which allows multiple receive signals from discrete antennas to be combined. Traditional methods of
receive diversity, as implemented in 802.11a/g devices, only switched to the antenna with the strongest
signal thus disregarding information available on the other antenna. In sharp contrast, by using multiple
antennas and advanced digital signal processing, 802.11n devices can decrypt both the original RF
transmission and subsequent reflected copies to form a more reliable ‘super’ signal comprised of
information gained from all antennas. Put more clearly, a hypothetical person with three ears will hear
more information than a person with two. The same goes for Access Points and their respective number
of antennas. By having multiple RF ‘viewpoints’ an 802.11n device enjoys increased reliability in
comparison to a legacy device meaning packets will reach their destination on the first transmission
reducing time wasted via costly retries.