{"id":80041,"date":"2018-03-01T18:20:04","date_gmt":"2018-03-01T23:20:04","guid":{"rendered":"http:\/\/rbachnet.wwwmi3-ss40.a2hosted.com\/index.php\/"},"modified":"2021-08-04T20:33:39","modified_gmt":"2021-08-05T00:33:39","slug":"mimo-antennas-explained","status":"publish","type":"post","link":"https:\/\/rbach.net\/index.php\/mimo-antennas-explained\/","title":{"rendered":"MIMO Antennas Explained"},"content":{"rendered":"

\"MIMOWave 2 of the IEEE 802.11ac<\/a> Wi-Fi standard<\/strong> has been out for a while now. Wave 2 Wi-Fi can support speeds up to 2.3 Gbps<\/strong>. One of the techniques used to generate the increased speeds of the 802.11ac networks is multi-spacial streams<\/strong> or several streams of the same Wi-Fi signal radiating out from several antennas. The multiple antennas are the most noticeable indicator that an access point<\/a> is 802.11ac capable, especially in the consumer market.<\/p>\n

Multiple-Input Multiple-Output<\/h3>\n

\"\"<\/a>The technology behind using several antennas is called Multiple-Input Multiple-Output<\/a> (MIMO<\/strong>). MIMO antennas have two or more antennas in a single physical package and are designed for use in IEEE 802.11n\/ac Wi-Fi networks. MIMO makes antennas work smarter by utilizing multiple antennas<\/strong> to combine data streams arriving from different paths and at different times to increase data throughput and range compared to a single antenna using the same radio transmit power. By transmitting multiple data streams at the same time, wireless capacity is increased<\/strong>.<\/p>\n

Additionally MIMO antennas improve link reliability and experience less fading than a single antenna system. MIMO antennas use spatial diversity technology, which puts surplus antennas to good use. When there are more antennas than spatial streams, the antennas can add receiver diversity and increase range<\/strong>.<\/p>\n

Radio-wave multipath<\/h3>\n

\"Asus<\/a>MIMO technology takes advantage of a natural radio-wave phenomenon called multipath<\/strong> to improve wireless performance. In the past, multipath caused interference and slowed down wireless signals. With this iteration, Wi-Fi takes advantage of multipath. With multipath transmitted information bounces off walls, ceilings, and other objects, reaching the receiving antenna multiple times via different angles and at slightly different times<\/p>\n

MIMO technology takes a single data stream and breaks it down into several separate data streams and sends it out over multiple antennas. This technique provides redundancy. The receiving MIMO antenna will “look” at each stream being sent to determine the strongest one to choose.<\/p>\n

Legacy wireless devices use Single-Input Single-Output (SISO) technology. These devices cannot take advantage of multipath, and can only send or receive one spatial stream at a time.<\/p>\n

802.11ac Wave 2 MIMO<\/h3>\n

\"\"<\/a>A new version of MIMO has been developed. TechHive<\/em><\/a> reports<\/a> that Multi-user multiple-input, multiple-output (MU-MIMO<\/strong>) technology, enables AP’s to transmit and receive data from multiple Wi-Fi devices at the same time<\/strong>. Although the devices must also support MU-MIMO to utilize it, they aren\u2019t required to have multiple antennas.<\/p>\n

MU-MIMO was introduced with 802.11ac Wave 2. Wave 2 MU-MIMO support is required on both the access point and client device<\/strong> to work. It operates in the downstream direction, access point to the client, and allows an access point to transmit to multiple client devices simultaneously. This means networks with a dense number of users in an area, such as public Wi-Fi hotspots, could be able to handle more Wi-Fi devices.<\/p>\n

TechHive<\/em> warns the biggest caveat of MU-MIMO is it doesn\u2019t directly improve the wireless speeds of uplink<\/em> connections.<\/p>\n

Only a handful meet the criteria today<\/h3>\n

\"MU-MIMO<\/a>It\u2019s also important to note that the only way to gain the full benefit of MU-MIMO is when the technology is supported on both the access point and the device that\u2019s connecting to the AP. So in addition to having an 802.11ac adapter onboard, the client must explicitly support MU-MIMO\u2014there are only a handful of adapters that meet that criteria today.<\/p>\n

Finally, TechHive<\/em> says MU-MIMO works best with stationary Wi-Fi devices. If users are walking around while watching a video on a smartphone or tablet, they are not going to get the full benefit of MU-MIMO even if that device supports it. Your router might even limit that connection to using SU-MIMO, so that the connection doesn\u2019t negatively impact stronger MU-MIMO connections.<\/p>\n

rb-<\/em><\/strong><\/p>\n

The client issue is the main reason 802.11ac Wave 2 will not be widely used in the enterprise. it is a big issue to keep the clients up to date to match the AP version. In fact, Zeus Kerravala<\/a> at NetworkWorld<\/a> points out<\/a> that many of the high-volume manufacturers, such as Apple and Samsung, are skipping 802.11ac Wave 2 and plan to support IEEE 802.11ax<\/a> in the future.<\/em><\/p>\n

So skip Wave 2 devices in the enterprise and stick to an 802.11ac Wave 1 AP, and get exactly the same performance as its higher-priced Wave 2 counterpart.<\/em><\/p>\n

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