A RECAP – WHAT IS MU-MIMO?
MU-MIMO, which stands for Multi-User, Multi-Input Multi-Output, exists to solve a problem faced by its predecessor, Single-User MIMO (SU-MIMO). MIMO itself means that a router has multiple antennas, each capable of emitting one spatial stream of data. The issue with this is that most devices do not have that many antennas themselves, and are thus not capable of taking in the full data output of a router. Add the fact that SU-MIMO does not allow for the multiple antennas to serve different client devices at a time, and the result is wastage of the router's full capacity, called the MIMO gap.
Instead of pushing all the data to one device that can’t make use of it all, MUMIMO means that the spatial streams are split between the other devices that are connected to the network.
MU-MIMO closes this gap by splitting its individual spatial streams to serve one device each, resulting in, theoretically, an equally high speed enjoyed by up to four devices per router or access point. With MUMIMO and devices supporting this technology, the multiple streams are spread out among the clients, meaning each gets its own stream of data. Another result of this is the router is capable of sending more data out at a time, closing the MIMO gap.
Still, MU-MIMO has some drawbacks of its own, chief among which being adoption. So far, there are few client devices out there that support MU-MIMO, and you will need such devices to truly take advantage of this feature. And while still faster than using a router that does not support MU-MIMO, if a device that does not support MU-MIMO connects to a MU-MIMO access point, other connected, MU-MIMO supported devices will experience a dip in speed. This is because the router will have to serve the legacy device with data the old-fashioned way – by pushing all four spatial streams of data to the device, despite the device being incapable to make full use of it. Other devices will also have to take turns in getting data from the router, to accommodate the device that doesn't support MU-MIMO.