所有现代互联网用户都知道Wi-Fi一词。这是一种无线连接到互联网的方式。Wi-Fi是Wi-Fi Alliance拥有的商标。该组织负责认证Wi-Fi产品是否符合 IEEE 制定的 802.11 无线标准(IEEE)。这些标准是什么？它们基本上是一组随着新频率可用而不断增长的规范。对于每一个新标准，目标都是提高无线吞吐量和范围。
如果您想购买新的无线网络设备，您可能会遇到这些标准。有许多不同的标准，每个标准都有自己的一套功能。仅仅(Just)因为一个新标准已经发布并不意味着它立即可供消费者使用，或者您需要切换到它。选择的标准取决于您的要求。
消费者通常会发现标准名称难以理解。这是因为IEEE(IEEE)采用的命名方案。最近(Recently)（2018 年），Wi-Fi联盟(Alliance)旨在使标准名称易于使用。因此，他们现在提出了易于理解的标准名称/版本号。然而，更简单的名称仅适用于最近的标准。而且，IEEE仍然参考使用旧方案的标准。因此，熟悉IEEE命名方案也是一个好主意。
Wi-Fi 标准说明：802.11ac、802.11b/g/n、802.11a
最近的一些 Wi-Fi 标准是 802.11n、802.11ac 和 802.11ax。这些名称很容易混淆用户。因此，Wi-Fi联盟(Alliance)给这些标准起的名称是——Wi-Fi 4、Wi-Fi 5 和 W-Fi 6。您可能会注意到所有标准中都有“802.11”。
什么是 802.11？(What is 802.11? )
802.11 可以被认为是开发所有其他无线产品的基础。802.11 是第一个WLAN标准。它由IEEE于 1997 年创建。它有一个 66 英尺的室内范围和一个 330 英尺的室外范围。802.11 无线产品由于其低带宽（几乎 2 Mbps）而不再生产。然而，围绕 802.11 建立了许多其他标准。
现在让我们来看看自第一个WLAN创建以来 Wi-Fi 标准是如何演变的。下面按时间顺序讨论自 802.11 以来出现的各种 Wi-Fi 标准。
1. 802.11b
尽管 802.11 是有史以来第一个WLAN标准，但使Wi-Fi流行的还是 802.11b。802.11 发布 2 年后，1999 年9 月(September 1999)，802.11b 发布。虽然它仍然使用相同的 802.11 无线电信号频率（约 2.4 GHz），但速度从 2 Mbps上升到 11 Mbps。这仍然是理论速度。实际上，预期带宽为 5.9 Mbps（对于TCP）和 7.1 Mbps（对于UDP）。它不仅是最古老的，而且是所有标准中速度最低的。802.11b 的范围约为 150 英尺。
由于它以不受管制的频率运行，因此 2.4 GHz(GHz)范围内的其他家用电器（例如烤箱和无绳电话）可能会造成干扰。通过将齿轮安装在远离可能产生干扰的电器的位置，可以避免这个问题。802.11b 及其下一个标准 802.11a 都同时获得批准，但首先进入市场的是 802.11b。
2. 802.11a
802.11a 与 802.11b 同时创建。由于频率不同，这两种技术不兼容。802.11a 以 5GHz 频率运行，不那么拥挤。因此，干扰的机会被最小化。但是，由于频率高，802.11a 设备的范围较小，信号不易穿透障碍物。
802.11a 使用称为正交频分复用 (OFDM)(Orthogonal Frequency Division Multiplexing (OFDM))的技术来创建无线信号。802.11a 还承诺提供更高的带宽——理论最大值为 54 Mbps。由于当时 802.11a 设备更昂贵，它们的使用仅限于商业应用程序。802.11b 是普通民众中流行的标准。因此，它比 802.11a 更受欢迎。
3. 802.11g
802.11g 于 2003 年6 月(June 2003)获得批准。该标准试图结合最后两个标准——802.11a 和 802.11b 所提供的好处。因此，802.11g 提供了 802.11a (54 Mbps ) 的带宽。但它通过在与 802.11b (2.4 GHz(GHz) )相同的频率下运行提供了更大的范围。虽然最后两个标准彼此不兼容，但 802.11g 向后兼容 802.11b。这意味着 802.11b 无线网络适配器可以与 802.11g 接入点一起使用。
这是仍在使用的最便宜的标准。虽然它为当今使用的几乎所有无线设备提供支持，但它确实有一个缺点。如果连接了任何 802.11b 设备，则整个网络会减慢以匹配其速度。因此(Thus)，除了是最古老的标准之外，它也是最慢的。
该标准是朝着更好的速度和覆盖范围的重大飞跃。这是消费者表示享受比以前标准覆盖范围更好的路由器的时候。(routers)
4. 802.11n
该标准也被Wi-Fi Alliance命名为Wi-Fi 4 ，于 2009 年(Wi-Fi 4)10 月(October 2009)获得批准。这是第一个使用MIMO技术的标准。MIMO 代表多输入多输出(MIMO stands for Multiple Input Multiple Output)。在这种布置中，许多发射器和接收器要么在链路的一端工作，要么甚至在链路的两端工作。这是一项重大发展，因为您不再需要依赖更高的带宽或传输功率来增加数据。
借助 802.11n，Wi-Fi变得更快、更可靠。您可能从LAN(LAN)供应商那里听说过术语双频。这意味着数据通过 2 个频率传递。802.11n 在 2 个频率下运行 - 2.45 GHz和 5 GHz。802.11n 的理论带宽为 300 Mbps。相信速度甚至可以达到450 Mbps如果使用 3 个天线。由于信号强度高，与以前的标准相比，802.11n 设备提供了更大的范围。802.11 支持广泛的无线网络设备。但是，它比 802.11g 贵。此外，在近距离使用 802.11b/g 网络时，可能会因使用多个信号而产生干扰。
另请阅读：(Also Read:) 什么是 Wi-Fi 6 (802.11 ax)？(What is Wi-Fi 6 (802.11 ax)?)
5. 802.11ac
该标准于 2014 年发布，是当今最常用的标准。802.11ac 被Wi-Fi Alliance命名为Wi-Fi 5。今天的家用无线路由器符合Wi-Fi 5标准，并以 5GHz 频率运行。它利用了MIMO，这意味着发送和接收设备上有多个天线。减少了错误和高速。这里的特点是，使用了多用户MIMO。这使它更加高效。在MIMO中，许多流被定向到单个客户端。在MU-MIMO 中(MU-MIMO)，空间流可以同时定向到多个客户端。这可能不会提高单个客户端的速度。但是网络的整体数据吞吐量显着增加。
该标准支持在其运行的两个频段（2.5 GHz和 5 GHz ）上的多个连接。802.11g 支持四个流，而此标准在 5 GHz(GHz)频段运行时支持多达 8 个不同的流。
802.11ac 实现了一种称为波束成形的技术。在这里，天线发射无线电信号，使它们指向特定的设备。该标准支持高达 3.4 Gbps的数据速率。这是数据速度第一次上升到千兆字节。提供的带宽在 5 GHz频段约为 1300 Mbps ，在 2.4 GHz频段约为450 Mbps。
该标准提供了最佳的信号范围和速度。它的性能与标准有线连接相当。但是，只有在高带宽应用中才能看到性能的提升。此外，它是实施成本最高的标准。
其他 Wi-Fi 标准(Other Wi-Fi standards)
1. 802.11ad
该标准于 2012 年12 月推出(December 2012)。这是一个非常快速的标准。它以令人难以置信的 6.7 Gbps速度运行。它工作在 60 GHz频段。唯一的缺点是射程短。只有当设备位于距接入点 11 英尺半径范围内时，才能实现所述速度。
2. 802.11ah
802.11ah 也称为Wi-Fi HaLow。2016年9月(September 2016)获批， 2017年5月(May 2017)发布。目的是提供一种低能耗的无线标准。它适用于超出通常 2.4 GHz和 5 GHz频段范围的(GHz)Wi-Fi网络（尤其是那些在 1 GH 频段以下运行的网络）。在此标准中，数据速度最高可达 347 Mbps。该标准适用于物联网(IoT)设备等低能耗设备。使用 802.11ah，可以在不消耗太多能量的情况下进行远距离通信。相信该标准将与蓝牙竞争(Bluetooth)技术。
3. 802.11aj
它是 802.11ad 标准的略微修改版本。它适用于工作在 59-64 GHz频段的地区（主要是中国(China)）。因此，该标准还有另一个名称——中国毫米波(China Millimeter Wave)。它在中国 45 (China 45) GHz频段运行，但向后兼容 802.11ad。
4. 802.11ak
802.11ak 旨在为具有 802.11 功能的设备提供 802.1q 网络内的内部连接帮助。2018(November 2018)年11 月，该标准处于草案状态。它适用于家庭娱乐和其他具有 802.11 功能和 802.3 以太网功能的产品。
5. 802.11ay
802.11ad 标准的吞吐量为 7 Gbps。802.11ay，也称为下一代60GHz，旨在在60GHz频段实现高达20Gbps的吞吐量。(Gbps)其他目标是——增加范围和可靠性。
6. 802.11ax
俗称 Wi-Fi 6，这将是Wi-Fi 5的继任者。它比Wi-Fi 5(Wi-Fi 5)有很多好处，例如在拥挤区域更好的稳定性、即使在连接多个设备时也能保持高速、更好的波束成形等……它是一种高效率的WLAN。预计将在机场等密集区域提供出色的性能。估计速度至少是Wi-Fi 5(Wi-Fi 5)中当前速度的 4 倍。它在相同的频谱下运行——2.4 GHz和 5 GHz。由于它还承诺提供更好的安全性并消耗更少的功率，因此未来所有的无线设备都将按照 Wi-Fi 6 标准进行制造。
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概括(Summary)
- Wi-Fi 标准是一组无线连接规范。
- 这些标准由IEEE引入，并由 Wi-Fi(IEEE)联盟(Alliance)认证和批准。
- 由于IEEE(IEEE)采用的令人困惑的命名方案，许多用户并不了解这些标准。
- 为了方便用户使用，Wi-Fi联盟(Alliance)重新命名了一些常用的 Wi-Fi 标准，并以用户友好的名称命名。
- 每个新标准都有附加功能、更快的速度、更远的范围等。
- 当今最常用的Wi-Fi标准是Wi-Fi 5。
Wi-Fi Standards Explained: 802.11ac, 802.11b/g/n, 802.11a
All modern internet users are aware of the term Wi-Fi. It is a way to connect to the internet wirelessly. Wi-Fi is a trademark that is ownеd by the Wi-Fi Alliancе. This organization is responsible for certifying Wi-Fi products if thеy meet the 802.11 wireleѕs standards set by the IEEE. What arе these ѕtаndards? They are basically a set of specifications that kеep growing as new frequencies become аvailable. With every nеw standаrd, the aim is to boost the wireless throughput and range.
You may come across these standards if you are looking to buy new wireless networking gear. There are a bunch of different standards each with their own set of capabilities. Just because a new standard has been released does not mean that it is immediately available to the consumer or you need to switch over to it. The standard to choose depends on your requirements.
Consumers usually find the standard names hard to understand. That is because of the naming scheme adopted by the IEEE. Recently (in 2018), the Wi-Fi Alliance aimed to make the standard names user-friendly. Thus, they have now come up with easy-to-understand standard names/version numbers. The simpler names are, however, only for the recent standards. And, IEEE still refers to the standards using the old scheme. Thus, it is a good idea to be familiar with the IEEE naming scheme too.
Wi-Fi Standards Explained: 802.11ac, 802.11b/g/n, 802.11a
Some of the recent Wi-Fi standards are 802.11n, 802.11ac, and 802.11ax. These names can easily confuse the user. Thus, the names given to these standards by the Wi-Fi Alliance are – Wi-Fi 4, Wi-Fi 5, and W-Fi 6. You may notice that all the standards have ‘802.11’ in them.
What is 802.11?
802.11 can be considered as the basic foundation upon which all other wireless products were developed. 802.11 was the first WLAN standard. It was created by IEEE in 1997. It had a 66-feet indoor range and a 330-feet outdoor range. 802.11 wireless products are no longer made because of its low bandwidth (hardly 2 Mbps). However, many other standards have been built around 802.11.
Let us now take a look at how the Wi-Fi standards have evolved since the first WLAN was created. Discussed below are the various Wi-Fi standards that came up since 802.11, in chronological order.
1. 802.11b
Although 802.11 was the first WLAN standard ever, it was 802.11b which made Wi-Fi popular. 2 years after 802.11, in September 1999, 802.11b was released. While it still used the same radio signaling frequency of 802.11 (about 2.4 GHz), the speed went up from 2 Mbps to 11 Mbps. This was still the theoretical speed. In practice, the expected bandwidth was 5.9 Mbps (for TCP) and 7.1 Mbps (for UDP). It is not only the oldest but also has the least speed among all the standards. 802.11b had a range of about 150 feet.
As it operates at an unregulated frequency, other home appliances at 2.4 GHz range (such as ovens and cordless phones) can cause interference. This problem was avoided by installing the gear at a distance from appliances that could potentially incur interference. 802.11b and its next standard 802.11a were both approved at the same time, but it was 802.11b that hit the markets first.
2. 802.11a
802.11a was created at the same time as 802.11b. The two technologies were incompatible because of the difference in frequencies. 802.11a operated at a 5GHz frequency which is less crowded. Thus, the chances of interference were minimized. However, due to high frequency, 802.11a devices had a lesser range and the signals would not penetrate obstructions easily.
802.11a used a technique called Orthogonal Frequency Division Multiplexing (OFDM) to create a wireless signal. 802.11a also promised a much higher bandwidth – a theoretical maximum of 54 Mbps. As 802.11a devices were more expensive at the time, their use was restricted to business applications. 802.11b was the standard prevalent among the common people. Thus, it has more popularity than 802.11a.
3. 802.11g
802.11g was approved in June 2003. The standard made an attempt to combine the benefits provided by the last two standards – 802.11a & 802.11b. Thus, 802.11g provided the bandwidth of 802.11a (54 Mbps). But it provided a greater range by operating at the same frequency as 802.11b (2.4 GHz). While the last two standards were incompatible with each other, 802.11g is backward compatible with 802.11b. This means that 802.11b wireless network adapters can be used with 802.11g access points.
This is the least expensive standard that is still in use. While it provides supports for almost all the wireless devices in use today, it does have a disadvantage. If there are any 802.11b devices connected, the whole network slows down to match its speed. Thus, apart from being the oldest standard in use, it is the slowest as well.
This standard was a significant leap towards better speed and coverage. This was the time when consumers stated enjoying routers with better coverage than the previous standards.
4. 802.11n
Also named Wi-Fi 4 by the Wi-Fi Alliance, this standard was approved in October 2009. It was the first standard that made use of MIMO technology. MIMO stands for Multiple Input Multiple Output. In this arrangement, many transmitters and receivers operate either at one end or even at both ends of the link. This is a major development because you no more have to depend on higher bandwidth or transmit power for an increase in data.
With 802.11n, Wi-Fi became even faster and more reliable. You might have heard the term dual-band from LAN vendors. This means that data is delivered across 2 frequencies. 802.11n operates at 2 frequencies – 2.45 GHz and 5 GHz. 802.11n has a theoretical bandwidth of 300 Mbps. It is believed that the speeds can reach even 450 Mbps if 3 antennae are used. Due to signals of high intensity, 802.11n devices provide a greater range when compared to those of previous standards. 802.11 provides support for a wide range of wireless network devices. However, it is more expensive than 802.11g. Also, when used in close range with 802.11b/g networks, there may be interference due to the use of multiple signals.
Also Read: What is Wi-Fi 6 (802.11 ax)?
5. 802.11ac
Released in 2014, this is the most common standard in use today. 802.11ac was given the name Wi-Fi 5 by the Wi-Fi Alliance. The home wireless routers today are Wi-Fi 5 compliant and operate at 5GHz frequency. It makes use of MIMO, which means there are multiple antennas on sending and receiving devices. There is reduced error and high speed. The specialty here is, a multi-user MIMO is used. This makes it even more efficient. In MIMO, many streams are directed to a single client. In MU-MIMO, spatial streams can be directed to many clients at the same time. This may not increase the speed of a single client. But the overall data throughput of the network is significantly increased.
The standard supports multiple connections on both the frequency bands at which it operates – 2.5 GHz and 5 GHz. 802.11g supports four streams while this standard supports up to 8 different streams when it operates in the 5 GHz frequency band.
802.11ac implements a technology called beamforming. Here, the antennae transmit radio signals such that they are directed at a specific device. This standard supports data rates up to 3.4 Gbps. This is the first time the data speed has risen to gigabytes. The bandwidth offered is around 1300 Mbps in the 5 GHz band and 450 Mbps in the 2.4 GHz band.
The standard provides the best signal range and speed. Its performance is on par with standard wired connections. However, the improvement in performance can be seen only in high-bandwidth applications. Also, it is the most expensive standard to implement.
Other Wi-Fi standards
1. 802.11ad
The standard was rolled out in December 2012. It is an extremely fast standard. It operates at an unbelievable speed of 6.7 Gbps. It operates at the 60 GHz frequency band. The only disadvantage is its short range. The said speed can be achieved only when the device is situated within an 11 feet radius from the access point.
2. 802.11ah
802.11ah is also known as Wi-Fi HaLow. It was approved in September 2016 and released in May 2017. The aim is to provide a wireless standard that exhibits low energy consumption. It is meant for Wi-Fi networks that go beyond the reach of the usual 2.4 GHz and 5 GHz bands (especially those networks that operate below the 1 GH band). In this standard, data speeds can go up to 347 Mbps. The standard is meant for low-energy devices such as IoT devices. With 802.11ah, communication across long ranges without consuming much energy is possible. It is believed that the standard will compete with Bluetooth technology.
3. 802.11aj
It is a slightly modified version of the 802.11ad standard. It is meant for use in regions that operate in the 59-64 GHz band (primarily China). Thus, the standard also has another name – the China Millimeter Wave. It operates in the China 45 GHz band but is backward compatible with 802.11ad.
4. 802.11ak
802.11ak aims to provide help with internal connections within 802.1q networks, to devices that have 802.11 capability. In November 2018, the standard had a draft status. It is meant for home entertainment and other products with 802.11 capability and 802.3 ethernet function.
5. 802.11ay
The 802.11ad standard has a throughput of 7 Gbps. 802.11ay, also known as the next-generation 60GHz, aims to achieve a throughput of up to 20 Gbps in the 60GHz frequency band. Additional objectives are – increased range and reliability.
6. 802.11ax
Popularly known as Wi-Fi 6, this will be the successor of Wi-Fi 5. It has many benefits over Wi-Fi 5, such as better stability in crowded areas, high speed even when multiple devices are connected, better beamforming, etc… It is a high-efficiency WLAN. It is expected to provide excellent performance in dense regions such as airports. The estimated speed is at least 4 times more than the current speed in Wi-Fi 5. It operates in the same spectrum – 2.4 GHz and 5 GHz. Since it also promises better security and consumes lesser power, all future wireless devices will be manufactured such that they are Wi-Fi 6 compliant.
Recommended: What is the Difference Between a Router and a Modem?
Summary
- Wi-Fi standards are a set of specifications for wireless connectivity.
- These standards are introduced by the IEEE and certified and approved by the Wi-Fi Alliance.
- Many users are not aware of these standards due to the confusing naming scheme adopted by the IEEE.
- To make it simpler for the users, the Wi-Fi Alliance has re-christened some commonly used Wi-Fi standards with user-friendly names.
- With every new standard, there are additional features, better speed, longer range, etc.
- The most commonly used Wi-Fi standard today is Wi-Fi 5.
