Will a legacy device slow down a MU-MIMO network?

Question

We've recently upgraded our router to the Asus RT-AC86U, which supports MU-MIMO on the 5GHz band.

With our previous SU-MIMO router, it was my understanding that one slow device (e.g. an old iPhone) could slow down the wireless speed of faster devices on the network. This was problematic given the very large local file transfers I do wirelessly.

I think I understand the benefits of MU-MIMO and separate spatial streams where both the router and devices support it. However, I'd like to know if older SU-MIMO devices will negatively impact performance of other devices on the 5GHz MU-MIMO network (so should be restricted to the 2.4GHz 802.11n band)?

Thanks!

Answer 1

No.

MU-MIMO on the router can only be helpful when more than one MU-MIMO-capable client is receiving data (streaming video, downloading files) at the same time.

The presence of “SU-MIMO” clients does not affect the ability of the MU-MIMO-capable router to send data via MU-MIMO simultaneously to multiple MU-MIMO-capable clients. But if you have more than one client receiving data at the same time, you would like them all to be MU-MIMO-capable otherwise you’re not getting the full potential benefit of MU-MIMO at that moment.