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CQI, PMI and RI relation in LTE

+3 votes

Want to know the relation between CQI and PMI/RI.

posted Aug 12, 2013 by Anderson

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2 Answers

+4 votes

All three used for feedback as expected by eNB from an UE to maximize the throughput with more reliability.
Channels conditions are more frequent to change. So Ue sends feedback to eNB about Ue is absorbing the radio. eNB receives all 3 parameters from UE then it consider all these parameters for next transmission of data.

CQI stands for channel quality indicator, based on received CQI value eNB uses proper modulation and coding rate for transport block.
PMI and RI comes into picture in case MIMO. There is a term "closed loop spatial multiplexing" . PMI is used for that purpose. for 4*4 MIMO there are 16 possible precoding matrix index.
RI is also used for MIMO. LTE UE supports max 2*2 MIMO. So R1 value ranges[1 - 2] based on Transmitter and receiver combination.
Frequency of reporting CQI is highest as compare to PMI/RI.
Even if RI and PMI related to MIMO schemes but both are independent to each other.

answer Aug 12, 2013 by Vimal Kumar Mishra
So in summary all three are independent
+1 vote

These all three are sends from UE to eNB, and it may possible only CQI sends or the all three sends. CQI tells the channel condition and based on CQI value eNB will select the MCS . PMI and RI will come in picture only in the case of MIMO. RI tells the number of layers and PMI tells the precoding matrix. these value are calculated on the basis of cqi-ReportConfig that comes in RRC Connection Setup and RRC Reconfiguration.

answer Aug 21, 2013 by anonymous