WiFi是一种无线网络技术，可让您将支持WiFi的设备连接到本地网络。使用WiFi，您可以在本地网络设备之间传输数据或连接到 Internet（如果连接可用）。大多数人可能都知道这一点，因为我们每天都在使用WiFi ，但(WiFi)WiFi究竟是如何工作的呢？
WiFi是无线电(WiFi Is Radio)
关于WiFi(WiFi)最基本的事实是它使用无线电波来传输信息。无线电波是我们所说的特定频率范围的电磁辐射。光是(Light)我们眼睛对光谱敏感的部分，但由与无线电波相同的“物质”组成。
WiFi 使用两种不同的频率进行传输：2.4Ghz 和 5Ghz。这分别是每秒 2,400,000,000 和 5,000,000,000 个周期。与频率仅为 100Mhz 的 FM 收音机相比，这是相当高的。
无线电波的确切频率对其特性有很大的改变。使用更高的频率，您可以将更多信息打包到信号中。但是，某些频率的范围不是很长。
不同的频率也以不同的方式穿透物质。某些频率可以从大气中反弹，因此您的发射器和接收器不需要视线即可工作。其他频率只是直接射入太空。如果您想与卫星通信，这很有用，如果接收器在地球上，那就没那么有用了。
如果您在传输功率中投入足够的功率，没有任何阻碍并使用正确的天线，那么WiFi工作频率的波可以达到数百英里。(WiFi)但是，标准的家用WiFi通常具有 30-50 米（约 100/150 英尺）之间的畅通范围。2.4Ghz WiFi覆盖范围更远，5Ghz WiFi速度更快。
WiFi是数字的(WiFi Is Digital)
WiFi是无线电，但它是数字(digital )无线电。这意味着无线电波被调制以携带数字代码。WiFi绝对包含数字信息。
最新最好的WiFi技术的理论速度限制为 4.8 Gbps，一次使用四个 1.2 Gbps数据流。那是每秒 600 兆字节！当然，理论速度是在实验室中在最佳条件下确定的，但即使在现实世界中，现代WiFi也非常快。
WiFi 有标准和协议(WiFi Has Standards & Protocols)
WiFi已经存在了很长时间。该技术的第一次商业迭代早在 1997 年就已经发布。电气和电子工程师协会(The Institute of Electrical and Electronics Engineers)( IEEE ) 编纂了WiFi标准，正式名称为IEEE 802.11。第一代WiFi被称为 802.11a，但随着时间的推移，开发了更新、更好的WiFi版本：
- 802.11a
- 802.11b
- 802.11g
- 802.11n
- 802.11ac
- 802.11ax
WiFi不完全向后兼容。您不会找到许多仍然可以与 802.11a 设备通信的现代设备。那里的许多WiFi设备都是“bgn”，并且将与这三个标准一起使用，它们都使用 2.4Ghz 频段。802.11ac 使用 5Ghz 频段，但这些路由器中的大多数都是“双频段”，并且还提供 2.4Ghz 以与使用旧标准的旧设备通信。
实际上，与WiFi的向后兼容性参差不齐，因为某些设备在每个各自的标准中都被锁定为特定的速度。较新的路由器可能不会让事情进展得那么慢！
顺便说一句，整个“802.11”命名约定已被删除。最新的 802.11ax 现在称为WiFi(WiFi 6) 6，802.11是WiFi 5，依此类推。
WiFi 已加密(WiFi Is Encrypted)
任何人都可以拦截WiFi无线电波，但由于数字加密(digital encryption)，他们不能简单地窃听正在发送和接收的内容。至少，如果您的WiFi网络受密码保护，情况就是如此。
您的WiFi密码也是加密密钥，因此任何有密码的人都可以看到所有未经过滤的数据包。这就是为什么您应该只使用启用了 HTTPS 的网站，并且如果您使用公共WiFi热点，请始终使用VPN服务！(VPN)
您的WiFi设备很可能使用WPA2。WPA是WiFi Protected Access的缩写，是一种非常强大的(WiFi Protected Access)WiFi连接加密方案。然而，多年来，黑客已经发现了各种漏洞，在某些情况下，这些漏洞可以让他们破解WPA2加密协议。
2018 年， WiFi技术的托管方WiFi 联盟( WiFi Alliance)宣布了 WPA3(WPA3)。这个新版本提高了安全性并填补了WPA2中发现的安全漏洞。当然，所有硬件都支持新的安全标准还需要一段时间。
WiFi Direct是一件事(WiFi Direct Is a Thing)
WiFi旨在使用诸如路由器之类的中央设备来管理设备之间的通信。但是，WiFi也可用于直接连接两个设备，即所谓的“点对点”连接。例如，当您想将大文件从您的智能手机发送到某人的智能手机时，这非常方便。
这也是通常用于将视频从手机投射到智能电视的WiFi类型。(WiFi)当您使用GoPro相机或某些WiFi相机无人机等设备时，您也在使用直接WiFi连接。蓝牙(Bluetooth)在点对点无线连接世界中获得了大部分关注，特别是因为它非常节能，但WiFi直连速度快且使用简单。
路由器、中继器和网状网络(Routers, Repeaters & Mesh Networks)
虽然现在直接WiFi连接很常见，但我们大部分时间都使用的WiFi采用了集线器和辐条设计。(WiFi)换句话说，您的所有WiFi设备都连接到一个中央设备，该设备充当中间人。对于大多数人来说，这将是常见的WiFi路由器。
现代路由器拥有多个天线，将不同的频段以及发送和接收WiFi数据的硬件分开。这些路由器还处理您的互联网连接和网络上的任何有线以太网(Ethernet)设备，允许有线和无线网络相互通信。
然而，正如我们上面所说，WiFi信号范围非常有限。这意味着您离路由器越远，信号强度越差。WiFi 中继器(WiFi repeater)可用于在覆盖范围边缘扩展该信号。
虽然中继器工作得很好，但“网状”WiFi(” WiFi)系统出现了新趋势。在这里，没有中央路由器。相反，几个较小的路由器分布在您的家中，相互连接并提供无缝的WiFi云。这是大型企业中最常使用的WiFi技术，但它已成为家庭使用的负担得起的技术。(WiFi)
超越 WiFi(Beyond WiFi)
WiFi比以往任何时候都在我们身边，因为现在各种设备都需要网络连接。然而，在无线数据传输方面， WiFi并不是唯一的竞争技术。在低功耗、短距离连接方面，蓝牙占据主导地位。(Bluetooth)蓝牙(Bluetooth)的未来版本甚至可能在速度和范围方面让WiFi物有所值。
然而，WiFi的最大竞争对手很可能是 5G。第五代蜂窝技术提供更便宜的数据速率和密集的城市覆盖。5G 可能不会取代家庭中的WiFi，但 5G 提供了公共 WiFi 热点的替代方案，公共WiFi热点之所以流行，主要是由于移动数据的高成本。
HDG Explains: How Does WiFi Work?
WiFi is a wireless networking technology that lets you connect your WiFi-enabled devices to a local network. Using WiFi you can transfer data between local network devices or connect to the internet, if a connection is available. Most people probably know this, since we all use WiFi every day, but how does WiFi actually work?
WiFi Is Radio
The most fundamental fact about WiFi is that it uses radio waves to transmit information. Radio waves are what we call a specific frequency range of electromagnetic radiation. Light is the portion of the spectrum our eyes are sensitive to, but is made of the same “stuff” as radio waves.
WiFi uses two different frequencies for transmission: 2.4Ghz and 5Ghz. That’s 2,400,000,000 and 5,000,000,000 cycles per second respectively. This is pretty high compared to FM radio which has a frequency of only about 100Mhz.
The exact frequency of a radio wave changes a lot about its characteristics. With a higher frequency, you can pack more information into your signal. However, some frequencies don’t have very long ranges.
Different frequencies also penetrate matter differently. Some frequencies can be bounced off the atmosphere, so your transmitter and receiver don’t need line-of-sight to work. Other frequencies just shoot straight out into space. That’s useful if you want to communicate with a satellite, not so much if the receiver is on Earth.
Waves at the WiFi operating frequencies can reach hundreds of miles if you put enough wattage into the transmission power, have nothing in the way and use the right antenna. However, standard household WiFi usually has an unobstructed range of between 30-50 meters (approx 100/150 feet). 2.4Ghz WiFi has the longer range, 5Ghz WiFi has higher speeds.
WiFi Is Digital
WiFi is radio, but it’s digital radio. That means the radio waves are modulated to carry digital code. WiFi is absolutely packed with digital information.
The latest and greatest WiFi technology has a theoretical speed limit of 4.8 Gbps, using four 1.2Gbps data streams at once. That’s 600 megabytes per second! Of course, theoretical speeds are determined in a lab under optimal conditions, but even in the real world modern WiFi is very fast.
WiFi Has Standards & Protocols
WiFi has been around for a long time.The first commercial iteration of the technology was released all the way back in 1997. The Institute of Electrical and Electronics Engineers (IEEE) codified the WiFi standard, which is officially known as IEEE 802.11. The first generation of WiFi is known as 802.11a, but as time went by newer, better versions of WiFi were developed:
- 802.11a
- 802.11b
- 802.11g
- 802.11n
- 802.11ac
- 802.11ax
WiFi is not fully backwards compatible. You won’t find many modern devices that can still communicate with 802.11a devices. Many WiFi devices out there are “bgn” and will work with those three standards, which all use the 2.4Ghz frequency band. 802.11ac uses the 5Ghz band, but most of these routers are “dual band” and also offer 2.4Ghz to talk to older devices using older standards.
In practice backwards compatibility with WiFi is spotty, since some devices are locked to certain speeds within each respective standard. Newer routers may not let things go that slowly!
Incidentally, the whole “802.11” naming convention has been dropped. The latest 802.11ax is now known as WiFi 6, with 802.11 being WiFi 5 and so on.
WiFi Is Encrypted
Anyone can intercept WiFi radio waves, but thanks to digital encryption they can’t simply eavesdrop on what’s being sent and received. At least, this is the case if your WiFi network is password protected.
Your WiFi password is also the encryption key, so anyone with the password can see all the data packets unfiltered. This is why you should only use websites that are HTTPS enabled and always use a VPN service if you’re using a public WiFi hotspot!
Your WiFi devices are most likely using WPA2. WPA is short for WiFi Protected Access and is a very strong encryption scheme for WiFi connections. However, over the years hackers have discovered various exploits that, in some cases, allow them to break the WPA2 encryption protocols.
In 2018 the WiFi Alliance, which is the custodian of WiFi technology, announced WPA3. This new version improves security and plugs the security holes found in WPA2. Of course, it will be some time before all hardware out in the wild will support the new security standard.
WiFi Direct Is a Thing
WiFi was designed to use a central device such as a router to manage communication between devices. However, WiFi can also be used to directly connect two devices in what’s known as a “peer-to-peer” connection. This is very handy when, for example, you want to send a large file to someone’s smartphone from yours.
This is also the type of WiFi that’s often used to cast video from a phone to a smart TV. When you use devices such as GoPro cameras or certain WiFi cameras drones, you’re also using a direct WiFi connection. Bluetooth gets most of the attention in the peer-to-peer wireless connection world, especially since it’s so energy efficient, but WiFi direct is fast and just as simple to use.
Routers, Repeaters & Mesh Networks
While direct WiFi connections are commonplace these days, the WiFi we all use most of the time make use of a hub-and-spoke design. In other words, all of your WiFi devices connect to a central device, which acts as the go-between. For most people, this is going to be the common WiFi router.
Modern routers boast multiple antennas, separating different frequency bands as well as the hardware that sends and receives WiFi data. These routers also handle your internet connection and any wired Ethernet devices on your network, allowing the wired and wireless networks to communicate with each other.
However, as we said above, WiFi signal ranges are pretty limited. Which means that the further you are from the router, the worse the signal strength is. A WiFi repeater can be used to extend that signal at the edge of the coverage range.
While repeaters work well enough, there’s a new trend towards “mesh” WiFi systems. Here, there’s no central router. Instead several smaller routers are spread across your home, connected to each other and providing a seamless cloud of WiFi. This is the WiFi technology most commonly used in large businesses, but it’s become affordable for home use.
Beyond WiFi
WiFi is around us more than ever, as all sorts of devices now have a need for a network connection. However, WiFi is not the only competing technology when it comes to wireless data transmission. Bluetooth rules the roost when it comes to low-power, short range connections. Future versions of Bluetooth may even give WiFi a run for its money when it comes to speed and range.
However, the biggest competitor to WiFi might very well be 5G. Fifth-generation cellular technology offers cheaper data rates and dense urban coverage. 5G may not replace WiFi in the home, but 5G offers an alternative to public WiFi hotspots, which have become popular mainly due to the high costs of mobile data.
