Hi Experts, need practical experienced answer.
In LTE Mu-MIMO which transmission mode will give more benefit, TM4 or TM9?
Also, does TM9 will have some issues with Carrier Aggregation?
“It is recommended that the DrxSimulAckNackAndCqiSwitch be turned on in CA scenarios. If the CaCqiAndAckAbnCtrlSwitch cannot be turned off due to UE compatibility issues, it is recommended that downlink MU-MIMO in TM9 be disabled.”
Vendor is Huawei.
You can use TM8 to extract maximum juice out of MU-MIMO.
I was not aware for tm4 used with MU-MIMO, I think it’s Huawei proprietary feature for TM4.
Even tm9 not recommended as we use CSI-RS signal there which used RE meant for Pdsch so increase overheads
TM4 can use MU-MIMO.
But if capacity is high not recommended.
Yes, I guess.
No it’s not Huawei. It’s Standard.
But Huawei recommends to use TM4 when capacity is high, then it will give you more benefit
I could not find it in Standard. Where have you seen? Please, can give reference?
They say when capacity is high it’s PRB is more than 80 percent your DL user throughput goes down.
Because scheduling users like CCE have to be checked before using.
If CCE is less than 50 percent you can using MU-MIMO.
I have also same thoughts that MU-MIMO with high number of users will affect the performance, plus according to my observation it will only improve capacity not user end throughput.
What are we expecting?
Yes Capacity will improve but not user DL throughput.
Beyond tm4 never worked.
Documentation is also saying that it will be difficult in pairing plus clashing with other features as well, gain will be reduced.
TM4 i guess is optimum.
Main is your CELLMIMOPARACFG setting and RANK parameter is more important too apart from MU-MIMO.
If such things are not proper MIMO gain will be less.
In Huawei LTE make PUCCH format2 allocation as random to have CQI improvement and cqifltoptswitch apart from that you will find good gain.
Do a trial if you can.
MU-MIMO goal is to increase the overall system capacity rather than increasing the peak connection throughput.
MU-MIMO start with TM5.
Yes, MU-MIMO is a part I too feel because we never tried MU-MMO in TM4.
That’s why not sure may be huawei has its own standards 
Only capacity gain. Don’t expect throughput gain.
Capacity gain also minimum only/
Does increase in MIMO order, say 64 or 128 helps improve capacity gain?
Actually in LTE FDD massive MIMO 32T32R, Huawei has technology called SSB (Static Shared Beam).
This cell will be splited to 4 sectors or beams.
And each sector/beam, TM4 UE can be scheduled indepently
So we can consider TM4 also work in MU-MIMO with LTE FDD 32T32R.
Very new and different concept.
So Experts, in short, what is the difference between TM9 and TM4?
What gain TM9 UE will get?
TM9 gives MIMO 4 layers.