MU-MIMO Explained

Looking for a great explanation of MU-MIMO technology in a one hour webinar? Check out the recorded webinar from Cambium College.


Because I have no experience with MU-MIMO technology I would like to ask about the necessary number of antenna elements needed to perform beamforming and MU-MIMO. 


Hi - you will find more information on MIMO and MU-MIMO HERE


I am not sure I understand your question fully... to be able to do any kind of beamforming, you'll need more than one antenna element, so that you can manipulate the beam pattern of the signal.  In the case of the 450m, we use 56 patch antennas, that act as an array to create up to 7 sub-sector (narrow) patterns to achieve Multi-User MIMO transmission to up to 7 separate Subscribers simultaneously.

Essentially, this is how we define MU-MIMO, and exactly what is described by the webinar in the first post of this thread... have you watched it?


Thank you very much for your answer.

I was confused because in a presentation of 450m I saw that "14x14 MIMO system allows simultaneous communication to up to seven SMs."

So, I thought that only 2 antenna elements needed for one spatial stream.


I'm sending you the relevant slide:


Exactly.  On the 450m there are seven 2x2 transceivers, which is where the "14x14" comes from.  All the subscribers in the system are 2x2 (V+H dual polarity) and have two tranceivers.

However, regarding beamforming and MU-MIMO, it is not as simple as certain antenna elements being assigned to a given SM.  It's actually a really complex set of algorithms that illuminate and phase the array such that the proper antenna beam is formed to maximize the grouping and allow simultaneous communications (while minimizing interference of the other signals).

Thanks a lot for your answers.

So, 450m has 56 patch antennas that create 7 beams (sub-sector patterns) and each beam is created using 56/7=8 patch antennas. 

It seems that 450m supports hybrid beamforming because the RF chains (7xRF chains for up to 7 subscribers) are less than the 56 patch antennas.


This is not how it works... the patches are energized and phased in many different ways. It is not one patch assigned to a given sub-beam.  They are nearly infinitely steerable and change with every TDD time slot (i.e. extremely fast changing).

The good news is that, as a user of this technology, you don't need to think about how the beams, nulls or sub-sector patterns are being formed, as the radio performs all of the calculations and algorithms on its own.  It does report the grouping results and statistics to best help you optimize your deployment.