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IEEE 802.11ac-2013

IEEE 802.11ac-2013 or 802.11ac is a wireless networking standard in the IEEE 802.11 set of protocols (which is part of the Wi-Fi networking family), providing high-throughput wireless local area networks (WLANs) on the 5 GHz band. The standard has been retroactively labeled as Wi-Fi 5 by Wi-Fi Alliance.

The specification has multi-station throughput of at least 1.1 gigabit per second (1.1 Gbit/s) and single-link throughput of at least 500 megabits per second (0.5 Gbit/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).

The Wi-Fi Alliance separated the introduction of ac wireless products into two phases ("waves"), named "Wave 1" and "Wave 2". From mid-2013, the alliance started certifying Wave 1 802.11ac products shipped by manufacturers, based on the IEEE 802.11ac Draft 3.0 (the IEEE standard was not finalized until later that year). Subsequently, in 2016, Wi-Fi Alliance introduced the Wave 2 certification, which includes additional features like MU-MIMO (down-link only), 160 MHz channel width support, support for more 5 GHz channels, and four spatial streams (with four antennas; compared to three in Wave 1 and 802.11n, and eight in IEEE's 802.11ax specification). It meant Wave 2 products would have higher bandwidth and capacity than Wave 1 products.

New technologies

New technologies introduced with 802.11ac include the following:

  • Extended channel binding
    • Optional 160 MHz and mandatory 80 MHz channel bandwidth for stations; cf. 40 MHz maximum in 802.11n.
  • 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% higher data rate 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, and 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

Features

Mandatory

  • Borrowed from the 802.11a/802.11g specifications:
    • 800 ns regular guard interval
    • Binary convolutional coding (BCC)
    • Single spatial stream
  • Newly introduced by the 802.11ac specification:
    • 80 MHz channel bandwidths

Optional

  • Borrowed from the 802.11n specification:
    • 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)
  • Newly introduced by the 802.11ac specification:
    • 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:

Scenario Typical client
form factor
PHY link rate Aggregate
capacity
(speed)
One-antenna AP, one-antenna STA, 80 MHz Handheld 433 Mbit/s 433 Mbit/s
Two-antenna AP, two-antenna STA, 80 MHz Tablet, laptop 867 Mbit/s 867 Mbit/s
One-antenna AP, one-antenna STA, 160 MHz Handheld 867 Mbit/s 867 Mbit/s
Three-antenna AP, three-antenna STA, 80 MHz Laptop, PC 1.30 Gbit/s 1.30 Gbit/s
Two-antenna AP, two-antenna STA, 160 MHz Tablet, laptop 1.73 Gbit/s 1.73 Gbit/s
Four-antenna AP, four one-antenna STAs, 160 MHz
(MU-MIMO)
Handheld 867 Mbit/s to each STA 3.39 Gbit/s
Eight-antenna AP, 160 MHz (MU-MIMO)

  • one four-antenna STA
  • one two-antenna STA
  • two one-antenna STAs
Digital TV, Set-top Box,
Tablet, Laptop, PC, Handheld
  • 3.47 Gbit/s to four-antenna STA
  • 1.73 Gbit/s to two-antenna STA
  • 867 Mbit/s to each one-antenna STA
6.93 Gbit/s
Eight-antenna AP, four 2-antenna STAs, 160 MHz
(MU-MIMO)
Digital TV, tablet, laptop, PC 1.73 Gbit/s to each STA 6.93 Gbit/s

Wave 1 vs. Wave 2

Wave 2, referring to products introduced in 2016, offers a higher throughput than legacy Wave 1 products, those introduced starting in 2013. The maximum physical layer theoretical rate for Wave 1 is 1.3 Gbit/s, while Wave 2 can reach 2.34 Gbit/s. Wave 2 can therefore achieve 1 Gbit/s even if the real-world throughput turns out to be only 50% of the theoretical rate. Wave 2 also supports a higher number of connected devices.

Data rates and speed

Modulation and coding schemes
MCS
index
Spatial
Streams
Modulation
type
Coding
rate
Data rate (Mbit/s)
20 MHz channels 40 MHz channels 80 MHz channels 160 MHz channels
800 ns GI 400 ns GI 800 ns GI 400 ns GI 800 ns GI 400 ns GI 800 ns GI 400 ns GI
0 1 BPSK 1/2 6.5 7.2 13.5 15 29.3 32.5 58.5 65
1 1 QPSK 1/2 13 14.4 27 30 58.5 65 117 130
2 1 QPSK 3/4 19.5 21.7 40.5 45 87.8 97.5 175.5 195
3 1 16-QAM 1/2 26 28.9 54 60 117 130 234 260
4 1 16-QAM 3/4 39 43.3 81 90 175.5 195 351 390
5 1 64-QAM 2/3 52 57.8 108 120 234 260 468 520
6 1 64-QAM 3/4 58.5 65 121.5 135 263.3 292.5 526.5 585
7 1 64-QAM 5/6 65 72.2 135 150 292.5 325 585 650
8 1 256-QAM 3/4 78 86.7 162 180 351 390 702 780
9 1 256-QAM 5/6 N/A N/A 180 200 390 433.3 780 866.7
0 2 BPSK 1/2 13 14.4 27 30 58.5 65 117 130
1 2 QPSK 1/2 26 28.9 54 60 117 130 234 260
2 2 QPSK 3/4 39 43.3 81 90 175.5 195 351 390
3 2 16-QAM 1/2 52 57.8 108 120 234 260 468 520
4 2 16-QAM 3/4 78 86.7 162 180 351 390 702 780
5 2 64-QAM 2/3 104 115.6 216 240 468 520 936 1040
6 2 64-QAM 3/4 117 130.3 243 270 526.5 585 1053 1170
7 2 64-QAM 5/6 130 144.4 270 300 585 650 1170 1300
8 2 256-QAM 3/4 156 173.3 324 360 702 780 1404 1560
9 2 256-QAM 5/6 N/A N/A 360 400 780 866.7 1560 1733.3
0 3 BPSK 1/2 19.5 21.7 40.5 45 87.8 97.5 175.5 195
1 3 QPSK 1/2 39 43.3 81 90 175.5 195 351 390
2 3 QPSK 3/4 58.5 65 121.5 135 263.3 292.5 526.5 585
3 3 16-QAM 1/2 78 86.7 162 180 351 390 702 780
4 3 16-QAM 3/4 117 130 243 270 526.5 585 1053 1170
5 3 64-QAM 2/3 156 173.3 324 360 702 780 1404 1560
6 3 64-QAM 3/4 175.5 195 364.5 405 N/A N/A 1579.5 1755
7 3 64-QAM 5/6 195 216.7 405 450 877.5 975 1755 1950
8 3 256-QAM 3/4 234 260 486 540 1053 1170 2106 2340
9 3 256-QAM 5/6 260 288.9 540 600 1170 1300 2340 2600
0 4 BPSK 1/2 26 28.8 54 60 117.2 130 234 260
1 4 QPSK 1/2 52 57.6 108 120 234 260 468 520
2 4 QPSK 3/4 78 86.8 162 180 351.2 390 702 780
3 4 16-QAM 1/2 104 115.6 216 240 468 520 936 1040
4 4 16-QAM 3/4 156 173.2 324 360 702 780 1404 1560
5 4 64-QAM 2/3 208 231.2 432 480 936 1040 1872 2080
6 4 64-QAM 3/4 234 260 486 540 1053.2 1170 2106 2340
7 4 64-QAM 5/6 260 288.8 540 600 1170 1300 2340 2600
8 4 256-QAM 3/4 312 346.8 648 720 1404 1560 2808 3120
9 4 256-QAM 5/6 N/A N/A 720 800 1560 1733.3 3120 3466.7

Several companies are currently offering 802.11ac chipsets with higher modulation rates: MCS-10 and MCS-11 (1024-QAM), supported by Quantenna and Broadcom. Although technically not part of 802.11ac, these new MCS indices are expected to become official in the 802.11ax standard (~2019), the successor to 802.11ac.

160 MHz channels, and thus the throughput might be unusable in some countries/regions due to regulatory issues that allocated some frequencies for other purposes.

Advertised speeds

802.11ac-class device wireless speeds are often advertised as AC followed by a number, that number being the highest link rates in Mbit/s of all the simultaneously-usable radios in the device added up. For example, an AC1900 access point might have 600 Mbit/s capability on its 2.4 GHz radio and 1300 Mbit/s capability on its 5 GHz radio. No single client device could connect and achieve 1900 Mbit/s of throughput, but separate devices each connecting to the 2.4 GHz and 5 GHz radios could achieve combined throughput approaching 1900 Mbit/s. Different possible stream configurations can add up to the same AC number.

Type 2.4 GHz band
Mbit/s
2.4 GHz band config
[all 40 MHz]
5 GHz band
Mbit/s
5 GHz band config
[all 80 MHz]
AC450 - - 433 1 stream @ MCS 9
AC600 150 1 stream @ MCS 7 433 1 stream @ MCS 9
AC750 300 2 streams @ MCS 7 433 1 stream @ MCS 9
AC1000 300 2 streams @ MCS 7 650 2 streams @ MCS 7
AC1200 300 2 streams @ MCS 7 867 2 streams @ MCS 9
AC1300 400 2 streams @ 256-QAM 867 2 streams @ MCS 9
AC1300 - - 1,300 3 streams @ MCS 9
AC1350 450 3 streams @ MCS 7 867 2 streams @ MCS 9
AC1450 450 3 streams @ MCS 7 975 3 streams @ MCS 7
AC1600 300 2 streams @ MCS 7 1,300 3 streams @ MCS 9
AC1700 800 4 streams @ 256-QAM 867 2 streams @ MCS 9
AC1750 450 3 streams @ MCS 7 1,300 3 streams @ MCS 9
AC1900 600 3 streams @ 256-QAM 1,300 3 streams @ MCS 9
AC2100 800 4 streams @ 256-QAM 1,300 3 streams @ MCS 9
AC2200 450 3 streams @ MCS 7 1,733 4 streams @ MCS 9
AC2300 600 4 streams @ MCS 7 1,625 3 streams @ 1024-QAM
AC2400 600 4 streams @ MCS 7 1,733 4 streams @ MCS 9
AC2600 800 4 streams @ 256-QAM 1,733 4 streams @ MCS 9
AC2900 750 3 streams @ 1024-QAM 2,167 4 streams @ 1024-QAM
AC3000 450 3 streams @ MCS 7 1,300 + 1,300 3 streams @ MCS 9 x 2
AC3150 1000 4 streams @ 1024-QAM 2,167 4 streams @ 1024-QAM
AC3200 600 3 streams @ 256-QAM 1,300 + 1,300 3 streams @ MCS 9 x 2
AC5000 600 4 streams @ MCS 7 2,167 + 2,167 4 streams @ 1024-QAM x 2
AC5300 1000 4 streams @ 1024-QAM 2,167 + 2,167 4 streams @ 1024-QAM x 2

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.

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 would be the first consumer-oriented notebook to be fully compliant with 802.11ac (albeit in its "draft 2.0" version).

Apple began implementing 802.11ac starting with the MacBook Air in June 2013, followed by the MacBook Pro and Mac Pro later that year.

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

Commercial handsets (partial list)

Commercial tablets

Chipsets

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