Why very few network deployed 4x4 MIMO & 256QAM?
It is expensive to have a second antenna.
And 256 QAM not many UE support it.
In Europe mainly all MNOS have DL MIMO 4x4 and 256 QAM.
But not in africa or other similar places.
I think these 2 technologies are not bringing more money to MNO.
Now there’s even UL 256 QAM.
The peak throughput is obiously increased, but maybe not very useful due to lack of terminal & radio condition.
In Europe there are terminals for 256 QAM a lot of them.
But RF conditions for 256 QAM and DL MIMO 4x4 are not so many.
For 256 QAm I think SINR needs to be better than 20 dB.
Brazil we have two of the big operators with 4x4 in the main cities for a while. Only one antenna is used, not two. The third one is rolling out since the last year, along with a digital sector split which divides a old 2x2 sector in 3 or 4 new digital sectors with 4x4. This is used in high density areas.
256Q is everywhere, but the gains are small due to high SINR requirements. it is worth remembering 4x4 gains are more from 4x2 than 4x4, the last one also required high SINR.
Not to forget higher modulation draws high power from UE too.