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Mar 02

The Difference Between SU-MIMO and MU-MIMO

The Difference Between SU-MIMO and MU-MIMO

One factor in choosing the access point for your solution is the number of antennas and the APs support for MIMO (or how many streams the access point supports in communications with the client).

The MIMO support is a factor in determining how many people can connect to the AP, the bandwidth each client gets and add ons that can come with the AP.

The MIMO Jargon

The new wave, 802.11ac, APs have a 3x3 or a 4x4 SU-MIMO. What this means is that these access points have either 3 antennas transmitting and 3 antennas receiving, or 4 transmitting and 4 receiving.

SU-MIMO means Single User- Multiple Input Multiple Output, while MU-MIMO means Multiple User - Multiple Input Multiple Output.

Firstly, what is MIMO?

MIMO stands for Multiple Input Multiple Output. We have multiple antennas which, at any given moment will be receiving from the clients, some will be transmitting to the clients. To extend on this, when you are purchasing an access point, you will see the amount of antennas it has - for example, wave 802.11ac normally has 3x3 or 4x4.

With the introduction of the 802.11ac Wave 2 standard, we now have two different MIMO standards - Single User (SU) and Multiple User (MU).

Single User MIMO

Single User MIMO is what majority of access points support. The way that Single User MIMO works is it only 'talks' to one client at any given time. The access point time slices through its clients very quickly, sending small packets to the client as it works through. Although this does bring down the throughput of the access point, it allows for the access point to 'talk' to any client in its range.

With the new standard of 802.11ac Wave 2 and the addition of MU-MIMO, this limitation has been resolved.


Multiple User MIMO

Multiple User MIMO is supported by the new 802.11ac Wave 2 access points. The way that Multiple User MIMO works is that it controls the spatial streams that it sends out from its antennas, so that it can follow the clients around this gives clients a constant stream of data, rather than small packets. By doing this, it allows for a much higher throughput, while still being able to talk to all clients in its range. The way the access point handles with more users than antennas is through an onboard controller which analyses the data that is sent to each client, then the AP creates a spatial stream, which sends multiple users their data over the same stream.


Cisco's MU-MIMO Access Point

Cisco has recently released its own MU-MIMO access point, the 3800 Series. The new 802.11ac Wave 2 has allowed the 3800's to provide a theoretical connection rate of up to 2.6Gbps per radio.

This doubles the rates offered by today's high end 802.11ac access points. The 3800 supports three spatial streams, MU-MIMO enables access points to split spatial streams between client devices, to maximise throughput. Cisco has enabled the access points to dynamically change their radio settings based on the wireless environment.

All these features that have been packed into Cisco's newest access point has made it the most versatile access point currently on the market.



Cisco 3700, SU-MIMO



SU-MIMO and MU-MIMO are significantly different, with MU upgrading everything about SU:a higher throughput and more clients. But, since MU-MIMO is still quite new and expensive at the time of this blog, implementing a whole solution of MU-MIMO would be expensive. If you are wanting to have benefits that MU-MIMO allows, implementing them in meeting rooms or offices, where there are people who will be constantly using it, and areas where there will be high loads may be the most cost effective solution.

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