In case of CQI aperiodic report, UE use PUSCH.
PUSCH can be used for CQI report only or PUSCH is for both CQI + UL data?
Yes aperiodic cqi uses DCI0 or RACH response.
PUSCH can use both UL DATA + CQI.
It can carry both CQI and UL data.
But aperiodic is needed.
Does CQI reporting mode periodic or aperiodic depends on transmission modes as well?
Actually CQI is just a part in PUCCH we have rank indicator and PMI too so it should play a part.
PUCCH format has CQI, RANK indicator and PMI.
So after DL assignment in periodic or aperiodic UE reports CQI, RI and PMI and then according it that eNodeB send MCS, QAM and so on and also if we have retranmisson enable we can more MCS but in high BLERr or poor RF this can be a issue.
If retransmission rate is very high.
PUCCH format2 has CQI.
This will answer your question.
So MIMO is also a part in PUCCH firmat be it SISO, MIMO.
Thats why in Huawei LTE if we just keep PUCCH format fixed it will behave as per that and in random it can fluctuates as per it wants.