MU-MIMO (multi-user, multiple input, multiple output) is a wireless technology that was introduced in the 802.11ac Wave 2 (Wi-Fi 5) standard. It allows a single access point (AP) to transmit data to multiple devices simultaneously. MU-MIMO dramatically improves performance and efficiency when APs are transmitting to client devices that support Wi-Fi 5 or Wi-Fi 6. 

How does MU-MIMO work?

MU-MIMO allows APs and their many antennas to transmit to multiple client devices at one time. That helps increase airtime efficiency so every client—regardless of what version of 802.11 it is running—gets the amount of airtime it's supposed to get based on the technology supported. A lower-speed client no longer slows the overall downlink throughput for others on the network.

What are the benefits of MU-MIMO?

MU-MIMO's benefits include:

- There are no more bottlenecks. Devices get on and off the network quicker, allowing more devices to be served. 

- Legacy devices—those that run 802.11a/b/g/n—will see a bump in performance. Due to the speed of MU-MIMO, 802.11ac Wave 2 clients will get on and off the network quicker. 

- 802.11ac Wave 2-enabled smartphones, laptops, and tablets will jump on the 5-GHz band, leaving 2.4-GHz bands for older devices.

What is the difference between MU-MIMO and SU-MIMO?

With SU-MIMO (single-user MIMO), the AP transmits one at a time to each client. MU-MIMO allows the access point to send multiple data packets to multiple clients over the same frequency. This means a lower-speed client won't hold back packet transmissions to other clients. 

Thanks to MU-MIMO, an AP can use its antenna resources to transmit multiple frames to different clients, all at the same time and over the same frequency spectrum.

Where is MU-MIMO best suited?

MU-MIMO is particularly well suited to bring-your-own-device (BYOD) situations where devices such as smartphones and tablets have only a single antenna. Another instance is in a large crowd where people are all using their devices to connect to the same bandwidth.