How n/w configure the uplink MIMO to the UE in LTE case?
IN ASN, there is only one IE.
The UE doesn`t select.
The eNodeB schedules it with a specific DCI, similar to Downlink.
I mean in other word, does enB use SRS reporting or something else to schedule uplink grant for MIMO?
Yes, sure, based on the triplet RI, PMI and CQI.
That would depend on each vendor.
Scheduling algorithms are not 3GPP.
So, yeah, maybe it can schedule SRS transmissions, monitor RSRP per antenna port on UL, BLER, SINR, etc…
If you have HedEx, usually it provides a good overview of such algorithms, but sure, it is true for Huawei only.
Even though, typically the basics are shared across vendors.
Does it work for UL MIMO as well in a FDD system?