The latest Qualcomm X55 chipset for 5G supports 2x2 for mmWave and 4x4 for sub-6Ghz
Have anyone seen more than 4x4 MIMO in LTE or 5G in a UE (Mobile or Modem)?
Samsung has AAU with 8x8 DL MIMO capability but there are no UEs for this.
This is normal because 4x4 DL MIMO in a drivetest is less than 5%.
8x8 DL MIMO would be less than 1%, it doesn"t worth investment effort.
Indeed, even 4x4 for mmWave would be complex, 8x8 in any form may be an overkill and shall be efficient in case of stationary devices.
That’s the max we have also seen yet.
In indoor stats depending on TX antenna separation (sometimes more than 10 meters between antennas) rank 4 can be seen up to 90% of the time.
So is useful in indoor 4x4 DL MIMO with indoor coverage.
8x8 require min 8 antennas in UE side right, and no UE have more than 4 I think as of now.
But not sure of FWA modems.
Maybe they have 8 antennas.
As I know, currently no commercial UE support more than 4x4 MIMO.
Huawei has TUE ( test equipment ) which can support 8x8 MIMO, with customized 8 antenna and baseband module, for testing SU-MIMO 8 layers in 5G.