CQI

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The CQI reflects channel quality. It is measured by the UE and reported to the eNodeB. The UE uses the CQI to inform the eNodeB scheduler of the downlink channel quality. The CQI reported by the UE to the eNodeB is obtained by quantizing the pilot SINR measured by the UE. The CQI is measured by the UE and generally refers to the downlink channel quality. The CQI of the UE reports a 4-bit index. Each index indicates the maximum channel efficiency that the UE can support when the IBLER is less than 10% in a certain scheduling mode (QPSK/16QAM/64QAM). That is, the highest-order MCS is used. 
The CQI reported by the UE is a 4-bit value. The eNodeB selects the MCS and transport block size (TBS) by reading and processing the value. The following table lists the mapping between CQIs, modulation modes, and bit rates.

Table 1: 4-bit CQI Table [Reference : 36.213 Table 7.2.3-1]

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Channel quality information (CQI), respectively, tells the base station scheduler the data rate the
terminal expects to be able to receive at a given point in time.

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