802.11ac Gigabit Wi-Fi: The Fifth Generation of Wi-Fi

802.11ac, also known as Very High Throughput (VHT) or Gigabit Wi-Fi or Giga Wireless or 5G WiFi, is a faster and more scalable version of 802.11n. Continuing the long-existing trends to break the Gigabit barrier with data rate over 1Gbps and new features to meet growing multiple data streams applications, Wi-Fi devices will see significant improvements in the number of clients supported by an 802.11ac access point (AP), a better experience for each client, and more available bandwidth for a higher number of parallel video streams.

Trend of WiFi Technologies:

  

Nominal Configuration Bandwidth (MHz) Number of Spatial Streams Constellation Size and Rate Guard Interval PHY Data Rate (Mbps) Throughput (Mbps)*
802.11a
All 20 1 64QAMr3/4 Long 54 24
802.11n
Min 20 1 64QAMr5/6 Long 65 46
Low-end product (2.4GHz only+) 20 1 64QAMr5/6 Short 72 51
Midtier product 40 2 64QAMr5/6 Short 300 210
Max product 40 3 64QAMr5/6 Short 450 320
Amendment max 40 4 64QAMr5/6 Short 600 420
802.11ac wave 1
Min 80 1 64QAMr5/6 Long 293 210
Low-end product 80 1 256QAMr5/6 Short 433 300
Midtier product 80 2 256QAMr5/6 Short 867 610
High-end product 80 3 256QAMr5/6 Short 1300 910
80 MHz amendment max 80 8 256QAMr5/6 Short 3470 2400
802.11ac wave 2
Low-end product 160 1 256QAMr5/6 Short 867 610
Midtier product 160 2 256QAMr5/6 Short 1730 1200
High-end product 160 3 256QAMr5/6 Short 2600 1800
Ultra-high-end product 160 4 256QAMr5/6 Short 3470 2400
Amendment max 160 8 256QAMr5/6 Short 6930 4900

*Assuming a 70% efficient MAC, except for 802.11a, which lacks aggregation.

+Assuming 40 MHz is not available due to the presence of other APs.

 

How 802.11ac accelerates 802.11n?

802.11ac achieves the raw speed increase by pushing on three different dimensions:

  • more channel bonding: increased from the max. of 40MHz in 802.11n, up to 80MHz (for 117% speed-ups) or even 160MHz (for 333% speed-ups) in 802.11ac.
  • Denser modulation: increased from 802.11n’s 64 quadrature amplitude modulation (QAM), to using 802.11ac’s 256QAM for 33% speed burst at shorter yet still usable range.
  • more multiple input, multiple output (MIMO): whereas 802.11n stopped at four spatial streams, 802.11ac goes all the way to eight spatial streams for 100% speed-ups.

 

Comparison of 802.11ac and 802.11n Technical Specifications 

 

  • Key Characteristics of 802.11ac: 

11ac promises room for growth by focusing on less-cluttered 5-GHz channels, doubling or quadrupling channel widths, using more efficient encoding, doubling maximum spatial streams and eventually letting wireless access points service multiple clients simultaneously.

  • 5GHz Frequency Band:

contrary to 802.11n, which operates in both the 2.4GHz and 5GHz frequency, 802.11ac devices will operate only in the 5GHz RF band, so dual-band AP and clients will continue to use 802.11n at 2.4GHz.

  • Channelization:

in addition to the 20MHz and 40MHz channel bandwidth supported by 802.11n today, 802.11ac includes a mandatory contiguous 80MHz and optional 160MHz channel bandwidth. Current spectrum availability for 802.11ac by geography:

 

  • New Modulation and Coding Scheme:

two key differences to 802.11n

    1. 802.11ac includes optional 256QAM used for 80MHz and 160MHz transmissions. 256QAM offers 33% greater throughput than a 64QAM at cost of less tolerance of bit errors in lossy signal.
    2. Only 10 single user MCS (0 to 9) are defined in 802.11ac, significantly fewer than the 77 MCS specified in 802.11n.
  • Multiple Spatial Streams:

802.11ac includes support for up to 8 spatial streams, versus 4 in 802.11n. 

  • Multiuser MIMO (MU-MIMO):

second generation products of 802.11ac (WAVE 2) should also come with a new technology Multiuser MIMO (MU-MIMO) whichis the major technological leaps of 802.11ac. Whereas 802.11n is like an Ethernet hub that can only transfer a single frame at a time to all its port, MU-MIMO allows an AP to send multiple frames to multiple clients at the same time over the same frequency spectrum, with multiple smart antennas, a MU-MIMO AP can behave like a wireless switch. MU-MIMO is particularly well suited to Bring-Your-Own-Device (BYOD) situations where the devices such as smartphones and tablets might only have a single antenna.

  • Energy Efficiency:

802.11ac promises a twofold increase in energy efficiency over the existing 802.11n. The increasing energy efficiency certainly has numerous benefits for the growing number of portable devices that integrate WiFi, which must work with small batteries and limited power consumption.

 

Examples of 802.11ac configurations (all rates assume 256QAM, rate 5/6)

802.11ac, also known as Very High Throughput (VHT) or Gigabit Wi-Fi or Giga Wireless or 5G WiFi, is a faster and more scalable version of 802.11n. Continuing the long-existing trends to break the Gigabit barrier with data rate over 1Gbps and new features to meet growing multiple data streams applications, Wi-Fi devices will see significant improvements in the number of clients supported by an 802,11ac access point (AP), a better experience for each client, and more available bandwidth for a higher number of parallel video streams.

 

DAXA-92802.11ac/na single band 3x3 PCIe mini card, QCA9890

delivers up to 1.3Gbps wireless data rates and target next-generation dual-band, dual-concurrent (DBDC) enterprise wireless access points for a variety of high-reliable and bandwidth-intensive video-over-wireless applications.

Extra Rx filter provides the excellent radio rejection against the interfering signal from the 2nd WiFi module on con-current 2.4 & 5GHz application to dramatically improve the data throughput/ range performance.

DAXB-81: 802.11ac/n/a single band 3x3 PCIe mini card, BCM4360

delivers up to 1.3Gbps PHY rates, targeted to provide the increased coverage and throughput performance requirement for high quality video and media applications in the home and enterprise.

 

DAXA-O1802.11ac/n/a single band 3x3 PCIe mini card, QCA9880

Rx Sensitivity Co-existence with 2.4GHz Interference Tx Power:

Unique Front End Module design allows co-located 5GHz RF standing up to -3dBm power injection from 2.4GHz to provide non-degraded Rx sensitivity on dual-band, dual-concurrent (DBDC) implementation.