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802.11ac Wave 2 FAQ

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发表于 2017-12-12 21:44:16 | 显示全部楼层 |阅读模式
   随着WLAN 的不断演进,现在已经开始普及802.11 ac  wave 2 了,  关于 802.11ac  Wave 2 是不是还有很多疑问?比如它比802.11 abgn 对比在速率,带宽,使用频段上的疑问,这里给你解答!

Q.    What is 802.11ac?  
     A.     802.11ac is a transformational wireless LAN technology that represents a significant performance increase over its highly successful predecessor, 802.11n. 802.11n provided the wireless connectivity speeds that businesses needed to embrace Wi-Fi in their day-to-day operations and let workers begin using wireless as their primary network medium of choice. The 802.11ac IEEE standard allows for theoretical speeds up to 6.9 Gbps in the 5-GHz band, or 11.5 times those of 802.11n (Table 1). 802.11ac is coming to market in two releases: Wave 1 and Wave 2.  
  
Table 1.       Comparing 802.11ac Wave 2, Wave 1, and 802.11n
  
     Q.    What’s the functional difference between 802.11ac Wave 1 and Wave 2?  
     A.     Wave 1 products have been in use in the market for about 2.5 years. Wave 2 builds upon Wave 1 with some very significant enhancements:  
  
●   Supports speeds to 2.34 Gbps (up from 1.3 Gbps) in the 5 GHz band
  
●   Supports multiuser multiple input, multiple output (MU-MIMO)
  
●   Offers the option of using 160-MHz-wide channels for greater performance
  
●   Offers the option of using a fourth spatial stream for greater performance
  
●   Can run in additional 5-GHz bands around the world
     Q.    What exactly do these Wave 2 enhancements do, and why do we need them?  
     A.     Table 2 describes the added features and why they are becoming necessary.  
  
Table 2.       802.11ac Wave 2 as a Business Enabler
     
Wave 2 Feature
Business Drivers and Trends
Detail
Up to 2.34 Gbps in the 5 GHz band
                ●  Hyper growth in mobile video usage, joining voice over IP      
Higher speeds and efficiencies provide the bandwidth to support latency-sensitive video and voice traffic, as well as high and growing densities of clients
Multiuser MIMO
(MU-MIMO)
                ●  High-density wireless: The continued shift to end-user mobility and the increasing volumes of Wi-Fi-enabled Internet of Things (IoT) devices      
                ●  Multiple connected devices per user      
                ●  Interest in the “all wireless office” user experience      
                ●  Provides concurrent downstream communications to multiple wireless devices for the first time for more efficient use of the spectrum      
                ●  Lets client devices get on and off the network faster, so more clients can use the network      
160-MHz channel width
High-speed delivery of large files and data access and movement
Delivers theoretical capacity up to 2.3 Gbps, as compared to:
                ●  450 Mbps with 802.11n      
                ●  1.3 Gbps with 802.11ac Wave 1      
Fourth spatial stream
Generally, the greater the number of receive antennas, the greater the distance that a particular data rate can be sustained, depending on environment
Supports four transmitting and receiving antennas; previous iterations supported three receive antennas
Additional 5-GHz channels
Greater number of channels provides greater bandwidth and flexibility for RF to move channels in instances of interference
There are about 37 separate channels in the 5-GHz frequency worldwide. Some have been used for other purposes or have not been allowed for Wi-Fi use. As these conditions change, 802.11ac Wave 2 will be able to operate in more and wider channels, providing additional bandwidth available to Wi-Fi and supporting more users, devices, and applications.
  
     Q.    What are the new data rates supported with Wave 2?  
     A.     Wave 2 is a superset of 802.11ac Wave 1. As such, it supports all the data rates of 802.11ac Wave 1. With the addition of support for 160-MHz-wide channels and the modulation and coding scheme (MCS) rates of 802.11ac, Wave 2 provides new maximum PHY rates based on the number of spatial streams and modulation shown in Figure 1.  
     Figure 1.      802.11ac Wave 2 Potential Throughput  
  
     Q.    What band and channels will 802.11ac Wave 2 operate on?  
     A.     In practice, both Waves 1 and 2 apply to the 5-GHz band only. The available bandwidth varies around the world, but today it is typically some subset of 5.15 to 5.35 and 5.47 to 5.85 GHz. The United States makes all of this subset available to WLANs (580 MHz). 802.11ac continues to enable 20- and 40-MHz channels but also adds 80- and 160-MHz channels for greater throughput. However, given that 160 MHz of relatively unused contiguous spectrum is difficult to find, there is an 80+80-MHz mode, which is simply the 160 MHz waveform split into two different 80-MHz frequency segments, enabling them to be placed more flexibly. Note that 20, 40, and 80 MHz are the   only mandatory channel bandwidths in 802.11ac.  
  
IEEE 802.11ac Standard Ratification and Deployment Timelines
     Q.    Why are there two 802.11ac “waves”?  
     A.     The 802.11ac IEEE standard is being introduced to the market in a series of “waves” (releases) of new products and technology. The reason is that the capabilities in 802.11ac are numerous, and delivering them in waves allows the industry to take advantage of many without having to wait for all capabilities to be available. The standard defines a framework that provides a significant step beyond 802.11n and allows for growth into the future.  
     Q.    When can we anticipate 802.11ac Wave 2 products?  
     A.     Many industry analysts expect that the initial consumer-focused products providing Wave 2 support will become available toward the middle of 2015 (Figure 2). Enterprise and carrier-class Wave 2 clients and infrastructure products will follow three to six months later. This is very similar to how the 802.11ac Wave 1 products were introduced to the market.  
     Figure 2.      Anticipated 802.11ac Wave 2 Deployment Timeline  
  
     Note that both consumer-class and enterprise-class products including features for Wave 2 will likely appear in the market before the Wi-Fi Alliance launches its certification program. Of course, any product launched into the market before certification may run the risk of noncompliance with interoperability between 802.11ac devices and clients. But Cisco is confident its access points will be certifiable by the Alliance once the certification program actually launches (expected in the middle to the second half of 2016).  
     Q.    When 802.11ac Wave 2 clients ship, will they be full-featured?  
     A.     It is expected that one- and two-spatial-stream clients will make up the bulk of Wave 2 clients, followed by three-spatial-stream clients. This is similar to what we see today with the mix of 802.11ac Wave 1 client devices. Consumer Wave 2 solutions are expected in mid-2015, and enterprise-class Wave 2 client solutions will emerge near the end of 2015.  

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平均得分5 (3 评价)
发表于 2017-12-13 17:16:07 | 显示全部楼层
全英文,没整明白
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平均得分2 (1 评价)
 楼主| 发表于 2017-12-14 10:00:01 | 显示全部楼层
jackyduys 发表于 2017-12-13 17:16
全英文,没整明白

   慢慢看就能看明白, 你配置思科WLC 也都是英文的, 你也可以放谷歌翻译去翻译一下
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平均得分4 (3 评价)
发表于 2018-2-14 16:18:42 | 显示全部楼层
技术进步很快。
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平均得分2 (1 评价)
发表于 2018-4-23 10:04:56 | 显示全部楼层
需要仔细研读一下
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平均得分0 (0 评价)
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