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LEVER Home > WiFi Wireless News and Tutorials > 802.11ac - Gigabit /sec WiFi

IEEE 802.11ac Tutorial - an Overview of 802.11ac

802.11ac - the new 5th Generation IEEE standard for Gigabit WiFi

802.11ac Training Course

LEVER Technology Group have introduced their new 802.11ac training course covering the emerging 802.11ac standard for Very High Throughput (VHT) Wireless networks:

World First - New 802.11ad Training Course

LEVER Technology Group have introduced the World's first training course covering the emerging 802.11ad standard for Ultra-high speed Wireless LANs:

Course 615: Understanding IEEE 802.11ad In Depth - 5 days, launched in the UK and running World-wide - contact us for details.

This is a unique, high-value training course covering existing 820.11abgn Wi-Fi networks - plus the emerging IEEE 802.11ad Wi-Fi WLAN standard, technologies, PHYsical and MAC layers in depth.

What is 802.11ac?

IEEE 802.11ac is the new draft standard for Gigabit WiFi.

802.11ac promises data rates of up to 1.73Gbps between an access point and a wireless client.

The terminology used by the 802.11ac Working Group - "Very High Throughput (VHT) for lower 6GHz band" - essentially means "data rates higher than those of 802.11n" .. "working in the 5GHz band".

The IEEE Task Group for 802.11ac (IEEE 802.11 TGac) published its first draft of 802.11ac on 20 January 2011 - the Initial Technical Specification Draft 0.1. The 802.11ac standard will support data rates of around 1Gbps by using advanced features over and above 802.11n, including:

  • 256-QAM modulation, with advanced coding schemes: this alone increases speeds by 33% compared with 802.11n's 64QAM.

  • 80MHz and 160MHz channels in the 5GHz band: 802.11ac's 80MHz and 160MHz channels provide 2x and 4x the throughput / capacity respectively compared with 802.11n's 40HMz maximum channel width.

  • MU-MIMO - Multi-User MIMO: MU-MIMO allows the transmission of data to multiple clients simultaneously - to increase WiFi cell capacity.

  • Up to 8 spatial streams (using Space Division Multiple Access - SDMA - where streams are not separated by frequency, but are resolved spatially): 802.11n supports up to 4x MIMO streams, but 802.11ac supports up to 8x spatial streams - to double throughput / capacity again.

It is important to note that 802.11ac will NOT work in the 2.4GHz band, since there is insufficient spectrum there for the 80MHz and 160MHz channel widths that 802.11ac will use.

LEVER whole-heartedly welcomes that fact that this, and another new WiFi standard, will finally abandon the 2.4GHz spectrum!

Why? - Contact us to find out!

5G WiFi?

802.11ac is now being termed by some as "5G WiFi - the 5th generation of Wi-Fi".

Actually, it's the 5th generation of 802.11 - which isn't the same as Wi-Fi - but it's likely that the term fifth generation WiFi will stick.

Another reason for the term 5G WiFi - somewhat obvious - is that 802.11ac will only work in the 5GHz frequency band.

IEEE 802.11ac will be the world's fastest and most reliable Wi-Fi standard for consumers and enterprises, designed to meet the explosive growth in content consumption, and the proliferation of wireless devices. Some of the golas of 802.11ac include improved link reliability, faster throughput, higher capacity, broader coverage and longer battery life.

  • Faster Throughput to support apps such as streaming video content to Internet / Smart TVs, phones, tablet and PCs.
  • Higher Capacity to support more wireless devices, which may also be in more "dense" environments.
  • Broader Coverage to extend range of operation from the AP (at a given data rate), with fewer "dead spots" or areas of poor coverage.
  • Longer Battery Life by sending and receiving data faster, wireless devices will lose less battery power to the WiFi adapter. Equally, users will spend less time watching their screens - waiting for data to arrive - so they will again consume less battery power.

What data rates will 802.11ac deliver?

802.11ac will be the first standard to introduce Multi-User MIMO - MU-MIMO. 802.11ac with MU-MIMO will allow simultaneous MIMO transmissions to different users - but using a single channel.

So, theoretically, an 8-antenna access point working with four two-antenna client stations - all sharing a 160MHz channel, could burst data at 1.73 Gbps to each station. That is - a burst rate of 6.93 Gbps!

We must always realise, however, that in order to achieve these higher throughput figures, you will need the highest specification 802.11ac client and AP equipment.

Moreover, you must in no way expect to achieve these 802.11ac data rates - which are actually maximum instantaneous transmit speeds - as real-world 802.11ac throughputs.

Why? - Because of the usual 802.11 overheads: frame headers, Preambles, Inter-Frame Spaces (quiet periods), Control Frames .. lower-bit-rate clients contending for the same channel; co-channel interference (mutual interference) - especially in WiFi networks that are not expertly designed .. .. and much more.

802.11ac speed enhancements and MU-MIMO are nonetheless key technologies for high-capacity WiFi wireless networks. For example, 802.11ac operating at 1Gbps should allow simultaneous streaming of three lightly-compressed HDTV channels.

In LEVER's view however, the users who stand to benefit the most from 802.11ac will be Enterprise Wi-Fi networks with medium-to-high user densities. This includes Universities, Colleges, Schools - in fact many situations where existing user applications currently only work well over switched/wired 100/1000 Mbps Ethernet networks.

802.11ac Speeds - Data Rate Throughput Tests

Update - February 2013:

LEVER performed some throughput testing with a SOHO-grade Asus RT-AC66U 802.11n/802.11ac router. We achieved 125 Mbps of actual throughput - disk-to-disk (after TCP/IP headers were stripped) - to a single client laptop, using a Netgear A6200 dual-stream 802.11ac USB 2.0 adapter. We were reasonably impressed!

This level of performance was achieved at the 802.11ac 866 Mbps associated data rate (using an 80 MHz channel and 2x spatial streams).

Those throughput tests, however, were limited by the throughput capabilities of the FTP server, since wired (Gigabit Ethernet) speeds weren't much faster ..

So we ran some optimised Iperf/Jperf tests .. and achieved one-way 802.11ac throughputs of up to 390 Mbps under the same conditions. This IS impressive!

We expect to achieve even higher throughput between two 3x3 MINO 802.11ac APs or 802.11ac wireless bridges - in the order of 200Mbps real-world throughput at Layer 7.

802.11ac Beamforming

Whereas 802.11n introduced different, optional methods for beamforming, IEEE 802.11ac also introduces a single, standardised method. This will increase the chances of beamforming being used by 802.11ac devices

Beamforming is the technique of using multiple RF chains and antennas to create a directional multi-element antenna. This allows the RF enegry in frame transmissions to be directed towards the intended recipient, and away from other users.

Beamforming can both increase signal strength at the reciever - hence increase the range of operation; and also increase Signal to Noise Ratio (SNR) - for both the intended receiver, and also for other devices in the area (since they receive less of what would be regarded as an interfering signal).

When will 802.11ac products become available?

According to PCWorld, Netgear was officially the first networking company with an 802.11ac Wi-Fi router, the company announced Thursday 26 April 2012. The R6300 reportedly operates at up to 1.3Gbps, which makes it (theoretically) more than four times as fast as current 2x2 MIMO 802.11n routers.

The 802.11ac standard was ratified 18 December 2013.

Enterprise-grade 802.11ac WiFi equipment is expected to became available late 2013 and is now the de-facto choice for new, enterprise-greade Wi-Fi networks.

In-Stat have predicted a potential 1 billion 802.11ac devices shipping in 2015.

However, as with 802.11n products, Wave 1 802.11ac devices will not support 8x8 MIMO, nor Multi-User MIMO (MU-MIMO).

802.11ac News

Quantenna say they are readying 8x8x8 MU-MIMO chipsets for 2015. This will be really significant for the capabilities of the WLAN.

Wave 1 802.11ac

Between July 2013 and December 2013, some 262 WLAN Wave 1 802.11ac products were certified by the Wi-Fi Alliance tests. Wave 1 products are based on a draft of the 802.11ac standard, and support what was then a stable subset of the 802.11ac standard that was later ratified in December 2013.

Wave 1 Wi-Fi Certified 802.11ac products have the following features:

Wave 1 products support 802.11ac using 20 MHz, 40 MHz and 80 MHz wide channels in the 5-GHz band. Use of the 5GHz band, and potentially of the 40MHz and 80MHz channel widths, can account for some immediate improvements in data rate and Wi-Fi network capacity.

802.11ac will lure more clients into the 5-GHz band, which frees-up the 2.4 GHz band for what we might now call legacy devices.

Clients operating in the 5GHz band get access to more spectrum. 802.11ac clients also make better use of the available 5GHz air time increasing network capacity even further.

802.11ac products can use on of eight or nine 40 MHz channels, or four / five non-overlapping 80 MHz channels, or a mix of both.

The 802.11ac dynamic channel width feature can change the channel width per-frame. 802.11ac starts with primary channel assignments, but can expand and contract the channel width for each frame transmission, sending larger frames faster by borrowing otherwise idle airtime from adjacent channels.

Wave 1 802.11ac products may also support 256 QAM, but this higher-density modulation can only be used in very-high-quality, low-interference environments, which often means between devices in the same room. For this reason, 256 QAM may be used less in business environments unless your Wi-Fi network has been design well.

Most Wave 1 802.11ac APs will support two or three spatial streams, using 3x3 SU-MIMO. However, many new 11ac clients - such as tablets and smartphones - are single-stream devices, just as most 802.11n smartphones are single-stream (SISO).

These factors, and more, results in a wide range of real-world data rates being used in practice. For example, a single-stream 802.11n client using a 40-MHz channel can at best reach 150 Mbps (less than 70Mbps throughput), while a single-stream 802.11ac client using an 80 MHz channel might achieve 433Mbps (around 200Mbps throughput).

An 802.11ac notebook might connect to an 11n AP at 450 Mbps, and to an 802.11ac AP at 1.3Gbps under the same conditions.

Note: As with all generations of Wi-Fi, application throughputs are still approximately 50% of the data rate at which wireless frames are transmitted which is approximately the data rate at which the client is reported as being associated to the AP.

Should deploy 802.11ac?

A frequently-asked question was: Should I wait for 802.11ac products to become available from my preferred vendor? As of April 2014, almost all Enterprise Wi-Fi vendors are shipping

Whether to deploy 802.11ac depends on a number of factors. It's important to realise that right now, all 802.11ac products are Wave 1 compliant. 802.11ac ratification and 802.11ac certification by the Wi-Fi Alliance will not happen until 2013.

In particular, MU-MIMO will not feature in Enterprise 802.11ac products until 2014.

It really is important understand the capabilities of different vendors' 802.11ac equipment - it certainly isn't all equal.

Contact us for vendor-neutral advice on what we expect the WLAN vendors to be doing with 802.11ac - Cisco, Cisco Meraki, Aruba, Ruckus, Juniper, Meru, HP, Aerohive, Motorola, Xirrus, AirTight, Ubiquiti and more.

PS: If you're interested in a Wi-Fi Manufacturer that isn't listed above - there's a reason. Contact us to find out more.

What is IEEE 802.11ad?

Meanwhile, there's the IEEE 802.11ad standard - for Very High Throughput in 60GHz spectrum (milli-metre wavelengths). 802.11ad will operate at instantaneous burst speeds of up to 7Gbps.

The IEEE 802.11ad Working Group have also now aligned with the Wireless Gigabit Alliance (WiGig). The resulting 60GHz wireless technogies will offer even higher data rates than 802.11ac, but only at relatively short distances - and where walls, ceilings and other obstructions don't appear in the path. 802.11ad and WiGig will therefore be more suitable for cable-replacement applications.

The primary benefit of operating at 60GHz is that there are hundreds of megahertz of spectrum available.

802.11ac WiFi Consultants

LEVER are industry-leading WiFi consultants, delivering independent and authoritative advice on WiFi Planning and Design; wireless Site Survey, wireless network troubleshooting, analysis and optimisation and much more.

Our skills in wireless network Survey, Analysis, Diagnosis and Remdiation are unrivalled.

Contact LEVER now for free, independent advice on all aspect of WiFi deployment and WiFi standards - not just 802.11ac!


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