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Wi-Fi Technology | 5th Generation Wifi Technology |802.11ac

The fastest current 802.11n Wi-Fi connections max out at around 150Mbps with one antenna, 300Mbps with two and 450Mbps with three antennas. 802.11ac connections will be roughly three times faster – so that’s 450Mbps, 900Mbps and 1.3Gbps respectively. Netgear, brilliantly, illustrates this with two pictures of motorways: the first picture, showing “Today’s Wi-Fi”, is normal, but the one labelled “3x speed with 802.11ac” is really blurry.

If you thought Wi-Fi couldn’t get much faster than 802.11n, think again. 802.11ac, dubbed 5G Wi-Fi, promises ridiculously fast wireless  connections, better range, improved reliability, improved power consumption and a free horse.

802.11ac is the latest evolution of Wi-Fi, and it should be particularly good for gaming and HD video streaming.

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 lowlag gigabit speeds. Also, device battery life is extended, since the device’s Wi-Fi interface can wake up, exchange data with its AP, then revert to dozing that much more quickly.

802.11ac achieves its raw speed increase by pushing on three different dimensions:

  • More channel bonding, increased from the maximum of 40 MHz in 802.11n, and now up to 80 or even 160 MHz (for 117% or 333% speed-ups, respectively)
  • Denser modulation, now using 256 quadrature amplitude modulation (QAM), up from 802.11n’s 64QAM (for a 33% 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% speed-up).

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 (midtier), or 1300 Mbps (high end) at the physical layer. Second-generation products 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-generation products should also come with a new technology, multiuser MIMO (MU-MIMO). Whereas 802.11n is like an Ethernet hub that can only transfer 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 where the devices such as smartphones and tablets might only have a single antenna.

802.11n introduced a “reduced inter frame spacing,” which reduces overheads between consecutive transmissions, but experience has shown that A-MDPU solves much the same problem, but even more efficiently. 802.11ac devices operating in 802.11ac mode are not permitted to transmit RIFS (as of Draft 3.0). 802.11n features that are not updated for 11ac (or explicitly forbidden for 802.11ac devices operating in 802.11ac mode) include all the 802.11n sounding options, including extension LTFs, the calibration procedure, antenna selection, PCO, LSIG TXOP protection, unequal modulation, 4×3 and 3×2 STBC modes, MCS32, and dual CTS protection. If you don’t know these terms, then no problem, because almost certainly you’ll never need to know them.

Upgrade to 802.11ac ||

IT administrators are in the fortunate position to be able to pick between two great technologies: (1) 802.11n with A-MPDU, MIMO, beamforming, and speeds from 65 to 450 Mbps within 40 MHz, and (2) 802.11ac with A-MPDU, MIMO, beamforming, and speeds from 290 to 1300 Mbps within 80 MHz. 802.11n is available today and is sufficient for a lot of customer use cases.

802.11ac is the future of wireless LANs, but Wi-Fi-certified 802.11ac APs are not yet available. 802.11ac can provide full HD video at range to multiple users, higher client density, greater QoS, and higher power savings from getting on and off the network that much more quickly.

Most IT administrators deploy new APs at the same time as they fit out a building or retrofit a space. For these, we recommend installing 802.11n APs today, because of the sheer value of 802.11n. Further, for investment protection, it is most desirable to install modular APs that are readily field-upgradable to 802.11ac. As 802.11ac APs become available, these users should automatically start installing 802.11ac APs since the incremental value of 802.11ac exceeds any reasonable price differential.

Also, IT administrators typically upgrade their APs on a three-, four-, or five-year schedule. These IT administrators should continue to upgrade their APs on schedule, since the capability of today’s APs significantly exceeds the capabilities of previous generations of APs. Until 802.11ac APs become available, that modular 802.11n APs be installed, so as to provide an upgrade path to 802.11ac.

**The Article collect from CISCO System.

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