واى-فاى حديث سريع
IEEE 802.11ac هى شبكة كمبيوتر لاسلكية معيار سى 802.11 قيد التطوير حاليا والتي يفترض أن توفر سرعة عالية للشبكات اللاسلكية المحلية ([WLAN]]) أقل منستة غيغاهرتز (ما هوالمعروف باسم الموجة (5 غيغاهرتز). نظريا، فإن هذه المواصفات يفترض أن تمكن محطة متعددة الإنتاجية WLAN ما لا يقل عن 1 جيجابت في الثانية الواحدة وبحد أقصى سرعة وصلة واحدة على الأقل 500 ميغابايت في الثانية الواحدة (500 ميغابت / ثانية). ويتم إنجاز هذا من خلال توسيع المفاهيم التي تتبناها 802.11n: إشارة الراديوواسعة النطاق الترددي (حتى 160 ميجاهيرتز), أكثر MIMO تيارات مكانية (up to 8), multi-user MIMO, and high-density modulation (up to 256 QAM).
On January 20, 2011, the Initial Technical Specification Draft 0.1 was confirmed by IEEE 802.11 TGac. Standard finalization is anticipated in late 2012, with final 802.11 Working Group approval in late 2013. According to a study, devices with the 802.11ac specification are expected to become common by 2015 with an estimated one billion spread around the world.
As of September 2011, there are no consumer devices implementing the draft specification.
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تكنولوجيات جديدة
- Wider channel bandwidths
- 80 MHz and 160 MHz channel bandwidths (vs. 40 MHz maximum in 802.11n)
- 80 MHz mandatory for stations (STAs), 160 MHz optional
- 80 MHz and 160 MHz channel bandwidths (vs. 40 MHz maximum in 802.11n)
- More MIMO spatial streams
- Support for up toثمانية spatial streams (vs. أربعة in 802.11n)
-
Multi-user MIMO (MU-MIMO)
- 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
- Multiple STAs, each with one or more antennas, transmit or receive independent data streams simultaneously
- Modulation
- 256-QAM, rate 3/4 and 5/6, added as optional modes (vs. 64-QAM, rate 5/6 maximum in 802.11n)
- Other elements/features
- Single sounding and feedback format for beamforming (vs. multiple in 802.11n)
- MAC modifications (mostly to support above changes)
- Coexistence mechanisms for 20/40/80/160 MHz channels, 11ac and 11a/n devices
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.
Example configurations
All rates assume 256-QAM, rate 5/6:
| Scenario | Typical Client Form Factor |
PHY Link Rate | Aggregate Capacity |
|---|---|---|---|
| 1-antenna AP, 1-antenna STA, 80MHz | Handheld | 433 Mbit/s | 433 Mbit/s |
| 2-antenna AP, 2-antenna STA, 80MHz | Tablet, Laptop | 867 Mbit/s | 867 Mbit/s |
| 1-antenna AP, 1-antenna STA, 160MHz | Handheld | 867 Mbit/s | 867 Mbit/s |
| 2-antenna AP, 2-antenna STA, 160MHz | Tablet, Laptop | 1.73 Gbit/s | 1.73 Gbit/s |
| 4-antenna AP, أربعة 1-antenna STAs, 160MHz (MU-MIMO) |
Handheld | 867 Mbit/s to each STA | 3.47 Gbit/s |
| 8-antenna AP, 160MHz (MU-MIMO) -- 1 4-antenna STA -- 1 2-antenna STA -- 2 1-antenna STAs |
Digital TV, Set-top Box, Tablet, Laptop, PC, Handheld |
3.47 Gbit/s to 4-antenna STA 1.73 Gbit/s to 2-antenna STA 867 Mbit/s to each 1-antenna STA |
6.93 Gbit/s |
| 8-antenna AP, أربعة 2-antenna STAs, 160MHz (MU-MIMO) |
Digital TV, Tablet, Laptop, PC | 1.73 Gbit/s to each STA | 6.93 Gbit/s |
References
- ^ "Official IEEE 802.11 Working Group Project Timelines". 2011-11-30.
- ^ "Proposed TGac Draft Amendment". IEEE. 2011-01-18.
- ^ Wentink, Menzo. "TGac Meeting Minutes – Los Angeles, Jan 2011". IEEE.
- ^ Murph, Darren (2011-02-08). "Study: 802.11ac devices to hit the one billion mark in 2015, get certified in 2048". Engadget.
- ^ de Vegt, Rolf (2008-11-10). "802.11ac Usage Models Document".
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