如果您研究自 2015 年夏天推出的无线路由器(wireless router)，您会发现它们中的大多数都在宣传一种称为MU-MIMO 或多用户 MIMO 的技术(MU-MIMO or Multi-User MIMO)，并且它们还承诺无线传输速度比传统无线路由器快四倍路由器。什么是MU-MIMO，除了一个您不理解的听起来很有趣的首字母缩写词？MU-MIMO在您的无线路由器(wireless router)上做了什么，您是否应该购买采用这种技术的路由器？阅读本指南并了解您需要了解的所有内容：
使用旧标准（SU-MIMO或 1x1 MU-MIMO）时设备如何连接到无线路由器
不支持MU-MIMO 的无线路由器使用(MU-MIMO use)所谓的SU-MIMO 方法通过无线(SU-MIMO method)电信道(radio channel)传输数据。SU-MIMO 代表单用户多输入多输出，(Single-User Multiple Input Multiple Output,)它意味着一个无线通道可以一次向(wireless channel)网络客户端(network client)发送和接收数据。SU-MIMO是 2009 年(SU-MIMO)10 月(October 2009)最终确定并发布的 802.11n 网络标准的一部分。所有支持 802.11n 标准最终版本的无线路由器都可以使用SU-MIMO 方法(SU-MIMO method)用于传输数据。使用这种方法时，路由器擅长发送和接收数据，但只能在一个方向上一次发送到一个客户端。如果您的无线路由器带有一根用于接收和发送数据的天线，则它一次只能连接到一个网络设备(network device)。假设您有三个用户，每个用户的设备都连接到路由器的WiFi 广播(WiFi broadcast)。路由器只能向第一个用户发送和接收数据。当第一个用户完成后，它会转到第二个用户，然后是第三个用户。
同时数据流的数量受使用的最小天线数量的限制。如果您的路由器有四个天线，在SU-MIMO中，您最多可以同时拥有四个数据流。例如，可以在两个天线上发送或接收的无线路由器(wireless router)可以同时处理两个用户。具有四个天线的路由器可以同时处理四个单独的流和最多四个客户端。由于在许多WiFi网络上，您有多个连接的无线客户端，每个客户端都请求访问其数据流，因此路由器就像机关枪一样(machine gun)安装在旋转木马上。它会非常快速地将数据位依次传送到多个设备。每个设备都轮流等待发送和接收数据，因此当新设备连接时，线路和等待时间会变得(wait become)更长。因此，您连接到使用SU-MIMO的(SU-MIMO)无线路由器(wireless router)的设备越多，延迟就越大，您为每个设备获得的速度就越慢。
注意：(NOTE:)在一些技术文档中，SU-MIMO被称为 1x1 MIMO。当您在本文后面看到使用1x1 MIMO时，请记住这一点。
以下是MU-MIMO在 WiFi 方面的作用：
MU-MIMO、多用户 MIMO 或多用户多输入多输出(Multi-User Multiple Input Multiple Output)是同时向多个客户端传输而不是一个客户端的能力，或者一次使用多个数据流将数据传输到网络客户端(network client)，从而提高速度的转移。使用这种传输方法(transfer method)，无线路由器可以一次在单个无线电信道上(wireless radio channel)与多个用户“交谈”，或者在同一信道上使用多个数据流与一个用户“交谈”。
在无线路由器和设备中可以找到不同类型的MU-MIMO实现：
- 2x2 MIMO - 它提供两个空间流，在同一信道或频率(channel or frequency)上无线发送和接收数据。对于此实施，您只需要两根天线，并且您可以同时连接最多两个客户端，每个流上一个。
- 3x3 MIMO - 它提供三个空间流，您需要三个天线。您最多可以同时连接三个客户端。
- 4x4 MIMO - 它提供四个空间流，您需要四个天线，并且您最多可以连接四个客户端。
- 8x8 MIMO - 在同一无线信道或同一频率上为最多四个客户端提供八个空间流（是的，这是正确的）。对于此实施，您需要八根天线。8x8 MIMO还不是主流技术(mainstream technology)。
在下图中，您可以看到支持 3x3 MIMO的路由器的表示，同时与三个设备通信。
当您的无线设备也支持MU-MIMO时会发生什么？
MU-MIMO的一个方面是无线客户端也可以支持这项技术。便宜(Cheap)的智能手机和平板电脑只有一根无线天线(wireless antenna)以降低制造成本，因此它们提供 1x1 MIMO。高级(Premium)智能手机和平板电脑通常有两个天线，可以从 2x2 MIMO中受益。经济实惠的笔记本电脑有两个 Wi-Fi 天线，可以受益于 2x2 MIMO，而更昂贵的笔记本电脑有三个天线，可以受益于 3x3 MIMO。ASUS PCE-AC88 无线(ASUS PCE-AC88 wireless) PCI -Express 网络(PCI-Express network)适配器率先实现 4x4 MIMO。任何人都可以在(desktop computer)用于WiFi 网络(WiFi network)连接的台式计算机。
MU-MIMO背后的理念不仅在于将更多设备同时连接到无线网络(wireless network)，还在于提高无线连接的速度。因此，您的网络设备提供以下MU-MIMO实施之一：
- 1x1 MIMO——这类设备只有一根天线，只能连接到一个无线流(wireless stream)。
- 2x2 MIMO - 它们有两个天线，可以同时连接到两个MIMO流。
- 3x3 MIMO - 具有三个天线并同时连接到三个MIMO流。
- 4x4 MIMO - 有四个天线并同时连接到四个MIMO流。
在您的网络中，您使用提供不同MIMO实现的不同类型的无线设备。假设您有一个4x4 MIMO的(MIMO)无线路由器(wireless router)。该路由器提供四个数据流。因此，您可以通过 1x1 MIMO(MIMO)将数据连接并同时传输到四部智能手机，因为每部智能手机仅使用一个流。或者，您可以将数据连接并同时传输到两台具有 2x2 MIMO的平板电脑、一台具有 3x3 MIMO的笔记本电脑和一部具有 1x1 MIMO的智能手机，或者如果它支持 4x4 MIMO ，则仅传输到一台设备。但是，该设备具有 4x4 MIMO将受益于传输速度比具有 1x1 MIMO的智能手机快得多。
MU-MIMO有什么优势？
如果您购买支持MU-MIMO传输的(MU-MIMO)无线路由器(wireless router)或网状WiFi 系统(WiFi system)，您将获得以下好处：
- 减少每个设备必须等待(Decreases the time each device has to wait)接收数据的时间
- (Increases the download speed)提高所有支持MU-MIMO 无线(MU-MIMO wireless)流的设备的下载速度
- 支持和不支持MU-MIMO的设备都(MU-MIMO)可以享受更好的 Wi-Fi 体验(enjoy a better Wi-Fi experience)
- 增加网络容量和(Increases network capacity and the number of devices)路由器可以同时处理的设备数量
MU-MIMO 的缺点
使用带有MU-MIMO 的(MU-MIMO)无线网状系统和路由器也有一些缺点：
- 它仅在使用 802.11ac 无线标准和 5 GHz WiFi 频率时有效(It works only when using the 802.11ac wireless standard and the 5 GHz WiFi frequency)。您无法在 2.4 GHz 频率(GHz frequency)和 802.11n 等旧标准上利用它。使用SU-MIMO会卡住2.4 GHz 频率(GHz frequency)。
- MU-MIMO 只提升下载速度，不提升上传速度(MU-MIMO increases only the download speed, not the upload speed)。
- 您需要具有 MU-MIMO 的路由器和具有 MU-MIMO 的网络设备(You need both a router with MU-MIMO and network devices with MU-MIMO)才能获得更快的下载速度。购买新计算机、智能手机和其他小工具时，您需要确保它们可与 802.11ac 无线网络配合使用并且支持 MU-MIMO 传输。
MU-MIMO 是什么时候发布的？
MU-MIMO 技术(MU-MIMO technology)是 802.11ac Wave 2 无线标准(wireless standard)的一部分，该标准由 Wi-Fi 联盟(issued by the Wi-Fi Alliance)于 2015 年夏天发布。2016 年6 月(June 2016)，Wi-Fi联盟(Alliance)扩展了他们的 Wi-Fi CERTIFIED 计划(CERTIFIED program)，包括来自 802.11ac Wave 2标准的规范。Wi-Fi Alliance是为我们带来无线产品、标准和技术的全球公司网络。该网络包括 500 多家公司，包括思科(Cisco)、高通(Qualcomm)、微软(Microsoft)、戴尔(Dell)、三星(Samsung)等知名企业、苹果(Apple)、英特尔(Intel)等。
我需要MU-MIMO吗？
现代家庭拥有越来越多的需要持续无线连接(wireless connectivity)的智能设备。即使您的某些设备不支持MU-MIMO，您仍然可以从购买具有MU-MIMO的(MU-MIMO)无线路由器(wireless router)中受益，因为它可以同时处理更多设备。如果您家中还有高级智能手机、笔记本电脑和游戏机，那么使用MU-MIMO的好处就会增加。我们建议，如果您家中有八台或更多设备连接到无线网络(wireless network)，您应该考虑购买带有MU-MIMO的 Wi-Fi 路由器。
哪些无线(Which wireless)路由器和网状WiFi系统支持MU-MIMO？
(MU-MIMO)所有现代无线路由器和网状WiFi系统都提供(WiFi)MU-MIMO ，这些系统是在 2015 年最终确定802.11ac Wave 2标准后发布的。在Digital Citizen，我们测试了许多 MU-MIMO 路由器和无线网状系统。以下是我们推荐的最佳选择：
- 高级版：华硕 RT-AC86U(ASUS RT-AC86U)、华硕 ROG Rapture GT-AC5300(ASUS ROG Rapture GT-AC5300)、TP-LINK AC3200、TP-LINK Archer C5400和TP-Link Deco M5
- 中档：华硕 Blue Cave(ASUS Blue Cave)、TP-LINK Archer C2600和Linksys EA7500 v2。
- 低端：ASUS RT-AC1200G+、TP-Link Archer C1200、TP-Link Archer C5 v4。
Wi-Fi联盟(Alliance)还提供了一个门户，您可以在其中找到所有支持 802.11ac Wave 2标准的设备，包括无线路由器、智能手机、计算机和平板电脑。访问他们的产品查找器(Product Finder)并浏览您感兴趣的产品类型。
您对MU-MIMO(MU-MIMO)有何体验？
您已经到了本文的结尾，希望我们已经回答了您关于MU-MIMO 技术(MU-MIMO technology)的问题。您(Did)是否购买了带有MU-MIMO的(MU-MIMO)无线路由器(wireless router)？如果你这样做了，你的经验是什么？您是否注意到您的(Did)WiFi 体验(WiFi experience)质量有任何改善？使用下面的评论表分享您的想法和经验。(Share)
Simple questions: What is MU-MIMO in WiFi? Do I need it?
If you stυdy the wireless routers that were launched since the summеr of 2015, you notice that most of thеm advertise a technology called MU-MIMO or Multi-User MIMO and they also promіse wireless transfеrs that are up to four times faster than on traditional routers. What is MU-MIMO еxcept for a funny-sounding acronym that yоu do nоt understand? What does MU-MIMO dо оn your wireless router and shоuld you buy a router with this technology? Read this guide and learn everything you need to know:
How devices connect to wireless routers when using older standards (SU-MIMO or 1x1 MU-MIMO)
Wireless routers that do not offer support for MU-MIMO use the so-called SU-MIMO method for transmitting data over a wireless radio channel. SU-MIMO stands for Single-User Multiple Input Multiple Output, and it means that one wireless channel can send and receive data to and from a network client at a time. SU-MIMO is part of the 802.11n networking standard that was finalized and published in October 2009. All wireless routers with support for the final version of the 802.11n standard can use the SU-MIMO method for transmitting data. When using this approach, routers are good at sending and receiving data, but only in one direction, to one client at a time. If you had a wireless router with one antenna that is used for receiving and sending data, it could connect only to one network device at a time. Let's assume that you have three users, each with their device connected to the WiFi broadcast by the router. The router can send and receive data only to the first user. When it is done with the first user, it goes to the second user and then to the third.
The number of simultaneous data streams is limited by the minimum number of antennas in use. If your router has four antennas, in SU-MIMO, you can have up to four data streams simultaneously. For example, a wireless router that can transmit or receive on two antennas can handle two users simultaneously. A router with four antennas can handle four separate streams and up to four clients simultaneously. Since on many WiFi networks you have multiple wireless clients that are connected, each requesting access to their data stream, the router acts like a machine gun mounted to a merry-go-round. It rattles off bits of data very quickly to multiple devices in turn. Each device waits its turn to send and receive data, so when a new device connects, the line and the wait become longer. Therefore, the more devices you connect to a wireless router that is using SU-MIMO, the bigger the latency becomes and the less speed you get for each device.
NOTE: In some technical documentation, SU-MIMO is referred to as 1x1 MIMO. Keep this in mind when you see 1x1 MIMO being used later in this article.
Here is what MU-MIMO does when it comes to WiFi:
MU-MIMO, Multi-User MIMO or Multi-User Multiple Input Multiple Output is the ability to transmit to several clients simultaneously, instead of just one, or to transfer data to a network client using multiple data streams at once and thus increase the speed of the transfer. With this transfer method, a wireless router can "talk" to more than one user at a time on a single wireless radio channel or to one user using multiple data streams on the same channel.
There are different types of MU-MIMO implementations that are found in wireless routers and devices:
- 2x2 MIMO - it offers two spatial streams of wirelessly transmitting and receiving data on the same channel or frequency. For this implementation, you need only two antennas, and you can simultaneously connect a maximum of two clients, one on each stream.
- 3x3 MIMO - it offers three spatial streams, and you need three antennas. You can simultaneously connect a maximum of three clients.
- 4x4 MIMO - it offers four spatial streams, you need four antennas, and you can connect a maximum of four clients.
- 8x8 MIMO - offers eight spatial streams on the same wireless channel or the same frequency to a maximum of four clients (yes this is correct). For this implementation, you need eight antennas. 8x8 MIMO is not yet a mainstream technology.
In the illustration below you can see a representation of a router with support for 3x3 MIMO, communicating simultaneously with three devices.
What happens when your wireless devices also have support for MU-MIMO?
One aspect of MU-MIMO is that wireless clients can also have support for this technology. Cheap smartphones and tablets have only one wireless antenna to reduce their manufacturing costs, so they offer 1x1 MIMO. Premium smartphones and tablets, often have two antennas and can benefit from 2x2 MIMO. Affordable laptops have two Wi-Fi antennas and can benefit from 2x2 MIMO while more expensive ones have three antennas and can benefit from 3x3 MIMO. The ASUS PCE-AC88 wireless PCI-Express network adapter is the first to implement 4x4 MIMO. Anyone can use it on a desktop computer for WiFi network connections.
The idea behind MU-MIMO is not only to simultaneously connect more devices to the wireless network but also to increase the speed of the wireless connection. Therefore, your network devices offer one of the following MU-MIMO implementations:
- 1x1 MIMO - such devices have one antenna and can connect to only one wireless stream.
- 2x2 MIMO - they have two antennas and can simultaneously connect to two MIMO streams.
- 3x3 MIMO - have three antennas and simultaneously connect to three MIMO streams.
- 4x4 MIMO - have four antennas and simultaneously connect to four MIMO streams.
In your network, you use different types of wireless devices that offer different MIMO implementations. Let's assume that you have a wireless router with 4x4 MIMO. This router provides four data streams. Therefore, you can connect and simultaneously transfer data to four smartphones with 1x1 MIMO because each smartphone uses only one stream. Alternatively, you can connect and simultaneously transfer data to two tablets with 2x2 MIMO, to one laptop with 3x3 MIMO and one smartphone with 1x1 MIMO or just to one device, if it offers support for 4x4 MIMO. However, that device with 4x4 MIMO will have the benefit of transfer speeds that are a lot faster than one smartphone with 1x1 MIMO.
What are the advantages of MU-MIMO?
If you buy a wireless router or mesh WiFi system with support for MU-MIMO transfers, you get the following benefits:
- Decreases the time each device has to wait to receive data
- Increases the download speed offered for all devices that support MU-MIMO wireless streams
- Both devices that support MU-MIMO and the ones that do not, enjoy a better Wi-Fi experience
- Increases network capacity and the number of devices that that router can handle simultaneously
The downsides of MU-MIMO
There are also disadvantages to using wireless mesh systems and routers with MU-MIMO:
- It works only when using the 802.11ac wireless standard and the 5 GHz WiFi frequency. You cannot take advantage of it on the 2.4 GHz frequency and older standards like 802.11n. The 2.4 GHz frequency is stuck with using SU-MIMO.
- MU-MIMO increases only the download speed, not the upload speed.
- You need both a router with MU-MIMO and network devices with MU-MIMO to get faster downloads. When buying new computers, smartphones, and other gadgets, you need to make sure that they work with 802.11ac wireless networks and that they support MU-MIMO transfers.
When was MU-MIMO released?
The MU-MIMO technology is part of the 802.11ac Wave 2 wireless standard, which was issued by the Wi-Fi Alliance in the summer of 2015. In June 2016, the Wi-Fi Alliance extended their Wi-Fi CERTIFIED program to include the specifications from the 802.11ac Wave 2 standard. Wi-Fi Alliance is the worldwide network of companies that bring us wireless products, standards, and technologies. The network includes more than 500 companies, including big names like Cisco, Qualcomm, Microsoft, Dell, Samsung, Apple, Intel and so on.
Do I need MU-MIMO?
Modern homes have an increasing number of smart devices that require constant wireless connectivity. Even if some of your devices do not offer support for MU-MIMO, you still benefit from purchasing a wireless router with MU-MIMO, just because it can handle more devices at once. If you also have premium smartphones, laptops, and consoles in your home, then the benefit of using MU-MIMO increases. We recommend that, if you have eight or more devices that connect to the wireless network in your home, you should consider purchasing a Wi-Fi router with MU-MIMO.
Which wireless routers and mesh WiFi systems support MU-MIMO?
MU-MIMO is offered in all modern wireless routers and mesh WiFi systems, that were released after the 802.11ac Wave 2 standard was finalized in 2015. Here at Digital Citizen, we have tested many MU-MIMO routers and wireless mesh systems. Here are the best that we recommend:
The Wi-Fi Alliance also offers a portal where you can find all devices that provide support for the 802.11ac Wave 2 standard, including wireless routers, smartphones, computers, and tablets. Visit their Product Finder and browse through the types of products that interest you.
What is your experience with MU-MIMO?
You have arrived at the end of this article and, hopefully, we have answered your questions about the MU-MIMO technology. Did you buy a wireless router with MU-MIMO? If you did, what is your experience with it? Did you notice any improvements in the quality of your WiFi experience? Share your thoughts and experiences using the comments form below.
