5G NR mapping CQI to MCS

5G NR
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Hello all. In 5G-NR, How the gNB map CQI to a MCS?

5G NR mapping CQI to MCS
5G NR mapping CQI to MCS1024×1024 211 KB

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gNodeB maps CQI (Channel Quality Indicator) to a MCS (Modulation and Coding Scheme) through a predefined mapping table.

The CQI to MCS mapping table is specified in 3GPP TS 38.214 (where you can find definition of physical layer procedures for data transmission in 5G-NR)

CQI table definitions provides the detailed mapping of CQI indices to modulation schemes and coding rates.

MCS tables define how the MCS index is used to determine the modulation (QPSK, 16QAM, 64QAM, 256QAM) and the transport block size (TBS).

You can find these tables in Section 5.2.2.1 of the document, which outlines how the CQI values reported by the UE are mapped to MCS indices that control the modulation and coding rate used for data transmission.

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In 5G-NR, the gNB (Next Generation Node B) assigns the CQI (Channel Quality Indicator) to an MCS (Modulation and Coding Scheme) through the following process:

  1. Channel measurement: The user equipment (UE) measures the channel quality and sends feedback information to the gNB, including the CQI.
  2. CQI: The CQI is a value that represents the channel quality, with values ranging from 0 (worst quality) to 15 (best quality).
  3. Mapping table: The gNB uses a predefined mapping table to assign the CQI to a specific MCS.
  4. MCS selection: The gNB selects the appropriate MCS according to the mapping table and the received CQI.
  5. Resource allocation: The gNB assigns transmission resources (such as bandwidth, power, and modulation) based on the selected MCS.

CQI-MCS Mapping Table:

CQI MCS Modulation Coding Rate
1-3 QPSK 1/2 Low
4-6 QPSK 2/3 Medium
7-9 16QAM 3/4 High
10-12 64QAM 5/6 Very High
13-15 256QAM 7/8 Optimal

Considerations:

  • The mapping table can vary based on the implementation profile and network conditions.
  • The gNB can dynamically adjust the mapping table depending on network conditions and UE performance.
  • MCS assignment may also consider other factors such as traffic load, interference, and UE mobility.

The gNB assigns the CQI to an MCS using a predefined mapping table, taking into account the channel quality and network conditions.