IEEE 802.11ac

IEEE 802.11ac is a wireless networking standard in the 802.11 family (which is marketed under the brand name Wi-Fi), developed in the IEEE Standards Association process, providing high-throughput wireless local area networks (WLANs) on the 5 GHz band. The standard was developed from 2011 through 2013 and approved in January 2014.

This specification has expected multi-station WLAN throughput of at least 1 gigabit per second and a single link throughput of at least 500 megabits per second (500 Mbit/s). This is accomplished by extending the air interface concepts embraced by 802.11n: wider RF bandwidth (up to 160 MHz), more MIMO spatial streams (up to eight), downlink multi-user MIMO (up to four clients), and high-density modulation (up to 256-QAM).

New technologies

New technologies introduced with 802.11ac include the following:

• Extended channel binding
  • Mandatory 80 MHz channel bandwidth for stations (vs. 40 MHz maximum in 802.11n), 160 MHz available optionally
• More MIMO spatial streams
  • Support for up to eight spatial streams (vs. four in 802.11n)
• Downlink Multi-user MIMO (MU-MIMO, allows up to four simultaneous downlink MU-MIMO clients)
  • Multiple STAs, each with one or more antennas, transmit or receive independent data streams simultaneously
    • “Space Division Multiple Access” (SDMA): streams not separated by frequency, but instead resolved spatially, analogous to 11n-style MIMO
  • Downlink MU-MIMO (one transmitting device, multiple receiving devices) included as an optional mode
• Modulation
  • 256-QAM, rate 3/4 and 5/6, added as optional modes (vs. 64-QAM, rate 5/6 maximum in 802.11n)
  • Some vendors offer a non-standard 1024-QAM mode, providing 25% more bandwidth compared to 256-QAM
• Other elements/features
  • Beamforming with standardized sounding and feedback for compatibility between vendors (non-standard in 802.11n made it hard for beamforming to work effectively between different vendor products)
  • MAC modifications (mostly to support above changes)
  • Coexistence mechanisms for 20/40/80/160 MHz channels, 11ac and 11a/n devices
  • Adds four new fields to the PPDU header identifying the frame as a Very High Throughput (VHT) frame as opposed to 802.11n's High Throughput (HT) or earlier. The first three fields in the header are readable by legacy devices to allow coexistence

Meru Networks has suggested that 802.11ac makes a wireless network employing the Single Channel Architecture substantially more effective. Traditional 802.11 networks are deployed as a Multiple Channel Architecture

Mandatory and optional features

• Mandatory features (carried over from 802.11a/802.11g)
  • 800 ns regular guard interval
  • Binary convolutional coding (BCC)
  • Single spatial stream
• New mandatory features (newly introduced in 802.11ac)
  • 80 MHz channel bandwidths
• Optional features (carried over from 802.11n)
  • two to four spatial streams
  • Low-density parity-check code (LDPC)
  • Space-Time Block Coding (STBC)
  • Transmit Beamforming (TxBF)
  • 400 ns short guard interval (SGI)
• Optional features (newly introduced in 802.11ac)
  • five to eight spatial streams
  • 160 MHz channel bandwidths (contiguous 80+80)
  • 80+80 MHz channel bonding (discontiguous 80+80)
  • MCS 8/9 (256-QAM)

New scenarios and configurations

The single-link and multi-station enhancements supported by 802.11ac enable several new WLAN usage scenarios, such as simultaneous streaming of HD video to multiple clients throughout the home, rapid synchronization and backup of large data files, wireless display, large campus/auditorium deployments, and manufacturing floor automation.

With the inclusion of USB 3.0 interface, 802.11ac access points and routers can use locally attached storage to provide various services that fully utilize their WLAN capacities, such as video streaming, FTP servers, and personal cloud services. With storage locally attached through USB 2.0, filling the bandwidth made available by 802.11ac was not easily accomplished.

Example configurations

All rates assume 256-QAM, rate 5/6:

Data rates and speed

Theoretical

Advertised

Products

Commercial routers and access points

Quantenna released the first 802.11ac chipset for retail Wi-Fi routers and consumer electronics on November 15, 2011. Redpine Signals released the first low power 802.11ac technology for smartphone application processors on December 14, 2011. On January 5, 2012, Broadcom announced its first 802.11ac Wi-Fi chips and partners and on April 27, 2012, Netgear announced the first Broadcom-enabled router. On May 14, 2012, Buffalo Technology released the world’s first 802.11ac products to market, releasing a wireless router and client bridge adapter. On December 6, 2012, Huawei announced commercial availability of the industry's first enterprise-level 802.11ac Access Point.

Apple Inc. is selling 802.11ac versions of its AirPort Extreme and AirPort Time Capsule products. Motorola Solutions is selling 802.11ac access points including the AP 8232. In April 2014, Hewlett-Packard started selling the HP 560 access point in the controller-based WLAN enterprise market segment.

Commercial laptops

On June 7, 2012, it was reported that ASUS had unveiled its ROG G75VX gaming notebook, which will be the first consumer-oriented notebook to be fully compliant with 802.11ac (albeit in its "draft 2.0" version).

In June 2013, Apple announced that the new MacBook Air features 802.11ac wireless networking capabilities, later announcing in October 2013 that the MacBook Pro and Mac Pro also featured 802.11ac.

As of December 2013, Hewlett-Packard incorporates 802.11ac compliance in laptop computers.

Commercial handsets

Commercial tablets

Chipsets

Source: Wikipedia, Google