Wifi standars

IEEE802.11ac: The Next Evolution of Wi-FiTM Standards

QUALCOMM, Incorporated
May 2012

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IEEE802.11ac: The Next Evolution of
Wi-FiTM Standards

Table of Contents

Executive Summary.............................................................................. 1
[1] Introduction ...................................................................................... 2
[2] New Features in 802.11ac ............................................................... 2
2.1 Mandatory 5 GHz Operation.................................................... 3
2.2 Wider Bandwidth..................................................................... 3
2.3 Higher Order Modulation ......................................................... 4
2.4 Higher Order MIMO ................................................................. 5
2.5 Multi-User MIMO (MU-MIMO) ................................................. 5
2.6 Dynamic Bandwidth Management ........................................... 6
2.7 Single-Method Closed Loop TransmitBeamforming .............. 8
2.8 Backwards Compatibility ......................................................... 9
[3] 802.11ac Usage Model Example: In-home HD content
distribution ....................................................................................... 9
[4] 802.11ac HD Content Distribution Performance............................ 10
[5] Conclusion..................................................................................... 11
[6] APPENDIX ..................................................................................... 12
6.1 Mandatory and Optional features in 802.11ac ...................... 12
[7] Glossary ......................................................................................... 12

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IEEE802.11ac: The Next Evolution of Wi-FiTMStandards

Executive Summary
Traditionally Wi-Fi® was a means for users to stay connected at home or in the
enterprise to the internet and check emails, or surf the web. Today, that trend is
rapidly changing whereby Wi-Fi is being used for content consumption such as
streaming music and videos. Demand for video content is driven by easy-to-use video
streaming services such as Netflix, YouTube,etc. Many users demand high-definition
(HD) video content on set-top-boxes, TVs, laptops, and on their mobile devices such
as smart phones and tablets. HD video content, as well as video content in general,
presents a challenge for existing Wi-Fi 802.11n based networks, as they suffer from
interference in the 2.4 GHz band.
802.11ac is the next evolution of the Wi-Fi standard that promises todeliver multiple
HD video streams simultaneously. It can reach maximum throughputs well above a
Gigabit per second. The 802.11ac specification mandates operation in the 5 GHz
band, where there is relatively less interference and more channels are available
compared to the 2.4 GHz band. 802.11ac achieves higher performance than 802.11n
by using more spatial streams, wider bandwidth, higherorder modulation, and
improved bandwidth management techniques. Downlink Multi-user MIMO (MUMIMO) 1 is an advanced feature defined in the 802.11ac standard that allows
simultaneous multiple transmissions from the access point (AP) to up to four client
stations (STAs). MU-MIMO mode increases client performance even with fewer
antennas. With the proliferation of smart phones that have limited...