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1. Executive Summary
802.11ac, the emerging standard from the IEEE, is like the movie The Godfather Part II. It takes something great
and makes it even better. 802.11ac is a faster and more scalable version of 802.11n. It couples the freedom of
wireless with the capabilities of Gigabit Ethernet.
Wireless LAN sites will see significant improvements in the number of clients supported by an access point (AP), a
better experience for each client, and more available bandwidth for a higher number of parallel video streams.
Even when the network is not fully loaded, users see a benefit: their file downloads and email sync happen at
low-lag gigabit speeds. Also, device battery life is extended, since the device’s Wi-Fi interface can wake up,
exchange data with its AP, and then revert to dozing that much more quickly.
802.11ac achieves its raw speed increase by pushing on three different dimensions:
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More channel bonding, increased from a maximum of 40 MHz with 802.11n up to 80 or even 160 MHz (for
speed increases of 117 or 333 percent, respectively).
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Denser modulation, now using 256 quadrature amplitude modulation (QAM), up from 64QAM in 802.11n
(for a 33 percent speed burst at shorter, yet still usable, ranges).
●
More multiple input, multiple output (MIMO). Whereas 802.11n stopped at four spatial streams, 802.11ac
goes all the way to eight (for another 100 percent speed increase).
The design constraints and economics that kept 802.11n products at one, two, or three spatial streams haven’t
changed much for 802.11ac, so we can expect the same kind of product availability, with first-wave 802.11ac
products built around 80 MHz and delivering up to 433 Mbps (low end), 867 Mbps (mid-tier), or 1300 Mbps (high
end) at the physical layer. Second-wave products may promise still more channel bonding and spatial streams,
with plausible product configurations operating at up to 3.47 Gbps.
802.11ac is a 5-GHz-only technology, so dual-band APs and clients will continue to use 802.11n at 2.4 GHz.
However, 802.11ac clients operate in the less crowded 5-GHz band.
Second-wave products could also come with a new technology, multiuser MIMO (MU-MIMO). Whereas 802.11n is
like an Ethernet hub that can transfer only a single frame at a time to all its ports, MU-MIMO allows an AP to send
multiple frames to multiple clients at the same time over the same frequency spectrum. That’s right: with multiple
antennas and smarts, an AP can behave like a wireless switch. There are technical constraints, and so MU-MIMO
is particularly well suited to bring-your-own-device (BYOD) situations in which devices such as smartphones and
tablets have only a single antenna.
802.11ac-enabled products are the culmination of efforts at the IEEE and Wi-Fi Alliance pipelines. IEEE 802.11ac
delivered an approved Draft 2.0 amendment in January 2012 and a refined Draft 3.0 in May 2012, with final
ratification occurring at the end of 2013.In parallel, the Wi-Fi Alliance adopted an early but very stable and mature
IEEE draft, namely Draft 3.0, and used that as the baseline for an interoperability certification of first-wave products
in mid-2013. Later, and more in line with the ratification date of 802.11ac (that is, after December 2013), the Wi-Fi
Alliance is expected to refresh its 802.11ac certification to include testing of the more advanced 802.11ac features.
This second-wave certification could include features such as channel bonding up to 160 MHz, four spatial
streams, and MU-MIMO. Overall, this arrangement closely follows how 802.11n was rolled out. As of February
2014, the launch date for Wave 2 certification is yet to be determined.
