IEEE 802.11 Evolution Continues

The Demand for Speed and Bandwidth, Including Backhaul and Emergence of New Applications Are the Drivers for the New Standards

By Ian Verhappen

The Institute of Electrical and Electronic Engineers released the next generation of its 802.11 wireless standards, IEEE 802.11ad-2012, abbreviated as 802.11ad or very high throughput (VHT) in late December 2012. The Technical Group that developed this specification worked in partnership with the Wireless Gigabit Alliance (WiGig), which, in cooperation with the WiFi Alliance, will test and certify compliance with the standards.

The demand for speed and bandwidth, including backhaul (e.g. xDSL, fiber, speed) and emergence of new applications such as high-definition (HD) content streaming and instant file transfers, are the drivers for the new standards. Use cases, including multi-media mesh, point-to-point backhaul, public safety mesh, video demos and factory floor automation, are potentially relevant in the industrial sector.

Category Use Case
4. Backhaul Multi-media mesh backhaul
Point-to-Point backhaul
5. Outdoor campus/ Auditorium    Video demos, tele-presence in auditorium Public safety mesh
6. Manufacturing Floor Manufacturing floor automation

 Three of the six usage model categories addressed in the IEEE802.11ad standard.

Support for backhaul of high data bursts as an alternative to fiber over short distances for back-up of controllers or associated databases might now be possible. Other possibilities include addressing the need to capture streaming video data in response to an incident, or to observe reactions in controlled settings without exposure of personnel, or connecting assembly lines with video placement rather than a wire harness, or…? Added implementations are limited only by your creativity now that you're no longer tethered to a cable.

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IEEE 802.11ad and soon-to-be released IEEE 802.11ac amendments build off IEEE 802.11n, modifying both the physical layers (PHY) and the 802.11 medium-access control layer (MAC) to enable operation in the 60-GHz frequency band. This will enable a maximum throughput of at least 1 Gbps and up to 7 Gbps, as measured at the MAC data service access point. The VHT versions of 802.11 are positioned as successors to high-throughput (HT) 802.11n, and are designed to be fully backwards compatible with previous versions.

Standard Release date Band (GHz) Bandwidth (MHz) Max Data Rate Advanced Antenna Technologies
802.11 1997 2.4 20 2 Mbps N/A
802.11b 1999 2.4 20 11 Mbps N/A
802.11a 1999 5 20 54 Mbps N/A
802.11g 2003 2.4 20 54 Mbps N/A
802.11n 2009 2.4, 5 20, 40 600 Mbps MIMO, up to 4 spatial streams
802.11ad 2012 60 2160 6.76Gpbs Beamforming
802.11ac 2013 5 40, 80, 160 6.93 GBps MIMO, MU-MIMO, up to 8 spatial streams

Like previous evolutions within WLAN, 802.11ac and IEEE802.11ad are designed to be fully backward-compatible with previous standards.

IEEE introduced multiple-input, multiple-output (MIMO) to 802.11n, and IEEE 802.11ac will expand this capability to support up eight spatial streams and multi-user MIMO (MU-MIMO). MU-MIMO allows a terminal to transmit/receive signals to/from multiple users in the same frequency band simultaneously, while single-user MIMO can only take advantage of MIMO to increase throughput.

Also, multiple-antenna configurations using beam-steering are an optional feature of the IEEE 802.11ad specification. Beam-steering can be employed to circumnavigate minor obstacles such as people moving around a room or a piece of furniture blocking line-of-sight transmission, but longer free-space distances (e.g. > 10m) and more substantial obstructions (e.g., walls, doors, etc.) will prevent transmission.

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Another feature added to the VHT protocols is "fast session transfer," which enables wireless devices to seamlessly transition between the ISM 60-GHz frequency band and the legacy 2.4-GHz and 5-GHz bands. Being able to move between the bands ensures that computing devices are always "best connected," enabling them to operate with optimal performance and range criteria. Because range is inversely proportional to frequency, 802.11ad has a relatively small radius, so "band hopping" will be important. As a result of the need to "band hop," devices are likely to have three radios: 2.4-GHz for general use, which may suffer from interference; 5-GHz for more robust and higher speed applications; and 60-GHz for ultra-high-speed in a room.

VHT expands the capability of wireless and opens up new opportunities within the industrial and office environment, but there are trade-offs and it's our job as engineers to understand them, so that we can use technology in the appropriate way. For now, it appears that VHT also means "very close device" (VCD) or, once we figure out how to effectively use it, "very handy tool."

The standard can be purchased as a PDF.

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