WIRELESS NETWORKING
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transfers within the same channel, using a technology called
multiple-input multiple-output (MIMO). 802.11ac goes a
step further by allowing up to eight antennas and eight
spatial streams for increased efficiency and higher data
throughput.
In addition to supporting more antennas and spatial
streams, 802.11ac uses wider channels which provide more
capacity and increased data rates. 802.11ac moved away
from the congested 2.4 GHz frequency band and operates
only on the 5 GHz band. This frequency offers five times
the capacity of 2.4 GHz with a much cleaner signal and
less interference. The use of 5 GHz band also allows more
channels and wider channel widths. 802.11ac adds 80
MHz and optional 160 MHz channels, while still supporting
mandatory 20 MHz and 40 MHz channels. The combination
of wider channel width with additional spatial streams
translates into data rates of up to 1.3 Gb/s per radio for
Wave 1 products, and eventually up to 6.9 Gb/s with Wave 2
products.
One of the most notable improvements with 802.11ac
is modulation. With improved modulation and coding
techniques, 802.11ac supports a higher order modulation of
256 quadrature amplitude modulation (QAM). This scheme
allows transmission of 8 bits per sub-carrier — versus 6 bits
per sub-carrier at 64 QAM with 802.11n — resulting in 33%
faster data rates.
Multiple Users
In addition to improved speed and capacity, 802.11ac
expands on the MIMO technology of 802.11n by offering
Multi-User MIMO (MU-MIMO). This technology a