The only thing techies love more than creating acronyms is the chance to create even longer ones. Such is the case with wireless acronym MIMO (multiple input, multiple output), which got some additional letters with the release of MU-MIMO a few years ago and is on the verge of becoming more popular with the release of the forthcoming 802.11ax wireless standard.
MU-MIMO代表的多用户，多输入，多输出，并且是由路由器和终端设备支持的无线技术。MU-MIMO是从单用户MIMO（SU-MIMO），其通常被称为MIMO下一进化。MIMO技术是，以帮助提高创建的被同时用于接收和发送无线路由器上的天线的数量，改善了无线连接的能力。
MU-MIMO technology is also sometimes referred to as Next-Gen AC or AC Wave 2, the AC part referring to the802.11ac标准协议. Standards older than 802.11ac (such as 802.11b, g and n) do not support MU-MIMO.
When the standard came out a few years ago, only routers and access points supported the technology. Since then, many endpoint devices now support MU-MIMO (Wi-Fi chipmaker Qualcomm has a设备列表– including iPhones versions 6, 6 Plus and later – that incorporate its 802.11ac MU-MIMO technology, and the Wi-Fi Alliance has a名单of more than 550 products with MU-MIMO technology).
MU-MIMO的工作原理与无线设备
MU-MIMO的成立是为了支持多个用户试图在同一时间访问无线网络环境。802.11协议的本质是用户先来先服务的基础上提供服务。
When multiple users begin accessing the router at or near the same time, congestion can be introduced as the router services the first user’s request while the second (and third, fourth, etc.) wait. While these times can be miniscule, it can add up with more devices (smartphones, tablets, computers, etc.) and users asking for resources. MU-MIMO helps this by allowing for multiple users to access router functions without the congestion.
Types of MU-MIMO implementations found in wireless routers
MU-MIMO technology breaks up the available bandwidth into separate, individual streams that share the connection equally. A MU-MIMO router can come in 2x2, 3x3 or 4x4 variations, which refer to the number of streams (two, three or four) that are created by the router (there’s also talk of 8x8未来在2018年).
我n simple terms, imagine you’re in line at the school cafeteria – you get served after the people in front of you get their sloppy joes. With MU-MIMO, instead of one lunch lady, you now get two, three or four lunch ladies, which lessens the time you need to wait.
However, there are some rules regarding this. First, the streams are spatial, which means if two devices are close to each other, they still have to share the same stream. Imagine that cafeteria scenario again, but this time the four lines that were created are now points on a compass. If you’re physically located in the south line, you have to wait with everyone else unless you move to east, north or west. In an office setting, if your adjacent coworker is streaming a video conference while you’re trying to download a super-large sales presentation, you’ll have to wait, unless you move to the other side of the office. This scenario assumes that the router/access point has enabled MU-MIMO and beamforming support.
Second, the technology only works for downlink connections. This is great for home users who will likely need faster speeds for 4K video streams and online gaming, but less useful for business workers who need faster uploads for content creation (such as video uploading) or two-way video conferencing applications.
Bidirectional MU-MIMO on the horizon
我n addition to supporting 8x8 arrays, the coming-soon 802.11ax standardaddresses the uplink portionMU-MIMO，给上传者更好的体验。Initial 802.11ax产品预计将出现在2018年，虽然该标准将无法完成，直到2019年年初该标准还设计了密集的环境中，如机场，体育场和城市公寓楼。
所以未来是光明的MU-MIMO，因为它扩展了其功能和更多的设备成为能够利用的好处。我们只是希望我们不需要任何更多的字母添加到此已经足够大的缩写。
Keith Shaw is a former Network World senior editor and writer of the Cool Tools column. He is now a freelance writer and editor from Worcester, Mass.