Data Rates in 802.11ac

Modulation and Data Rates in 802.11ac

CableFree Amber Crystal 802.11ac MIMO radio
CableFree Amber Crystal 802.11ac 2×2 MIMO Multi Radio Outdoor AP Router Base Station

IEEE 802.11ac is a WiFi standard used for indoor Access Points, Routers and outdoor Radios including the CableFree AC Range.  Chipsets using 802.11ac technology includes support for 256QAM modulation, MIMO antennas and wide channels, which can combine to offer high data rates for users.

Installers need to be careful with 802.11ac especially regarding channel planning and interference mitigation.

Responsible use of the 5GHz spectrum also needs to be considered, to avoid congestion for current and future users.

Theoretical Data Rates

This table gives raw airside data rates for a single stream (1×1 SISO).  For 2×2 MIMO, double the data rates shown.  For Net (user) data rates, these vary depending on traffic type and protocol.  For WiFi usage, around 50% is generally available.  For advanced streaming protocols such as CableFreeMAX, up to 80% is available.

Theoretical throughput for single spatial stream (in Mbit/s)
MCS
index[b]		 Modulation
type		 Coding
rate		 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 BPSK 1/2 6.5 7.2 13.5 15 29.3 32.5 58.5 65
1 QPSK 1/2 13 14.4 27 30 58.5 65 117 130
2 QPSK 3/4 19.5 21.7 40.5 45 87.8 97.5 175.5 195
3 16-QAM 1/2 26 28.9 54 60 117 130 234 260
4 16-QAM 3/4 39 43.3 81 90 175.5 195 351 390
5 64-QAM 2/3 52 57.8 108 120 234 260 468 520
6 64-QAM 3/4 58.5 65 121.5 135 263.3 292.5 526.5 585
7 64-QAM 5/6 65 72.2 135 150 292.5 325 585 650
8 256-QAM 3/4 78 86.7 162 180 351 390 702 780
9 256-QAM 5/6 N/A N/A 180 200 390 433.3 780 866.7

Advertised Data Rates

Type 2.4 GHz Mbit/s 5 GHz Mbit/s
AC600 150 433
AC750 300 433
AC1200 300 867
AC1300 400 867
AC1450 450 975
AC1600 300 1,300
AC1750 450 1,300
AC1900 600 1,300
AC2350 600 1,733
AC3200 600 2,600

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
WIFI Technology 802.11ac data rates
WIFI Technology 802.11ac Access Point Router indoor hotspot with high data rates

Mandatory and optional features

  • Mandatory features (carried over from 802.11a/802.11g)
  • New mandatory features (newly introduced in 802.11ac)
    • 80 MHz channel bandwidths
  • Optional features (carried over from 802.11n)
  • 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)

For more information

For More Information on CableFree WiFi products, please Contact Us and our team will be delighted to advise on a precise solution to match your exact requirements.
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