Mu-MIMO would help. The real problem is that energy between a unit and an AP is not in a pencil-thin RF laser-beam --- it is spread out. Other nodes hear that energy, and back off. If we had better control of point-to-point links, then you could have plenty of bandwidth. It's not as if the photon field cannot hold them all. When we broadcast in all directions, we waste energy, and we cause unnecessary interference to other receivers.
it was quite a while back but I read some press release about a manufacturer that would make an access point that had mechanically steered directional antennas. Unfortunately I don't think it ever made it to market.
That can help in one direction, but networks are bi-directional.
No matter how fancy and directive the antenna arrangement may be at the access point end, the other devices that use this access point will be using whatever they have for antennas.
The access point may be able to produce and/or receive one or many signals with arbitrarily-aimed, laser-like precision, but the client devices will still tend to radiate mostly-omnidirectionally -- to the access point, to eachother, and to the rest of the world around them.
The client devices will still hear eachother just fine and will back off when another one nearby is transmitting. The access point cannot help with this, no matter how fanciful it may be.
(Waiting for a clear-enough channel before transmitting is part of the 802.11 specification. That's the Carrier Sense part of CSMA/CA.)
