5G/NR - DCI 详解

The main purpose of DCI (Downlink Control Information) is the same as DCI in LTE(I strongly recommend you to read LTE DCI page first if you are not so familiar with what the DCI does). That is, it is a special set of information which schedules downlink data channel (e.g, PDSCH) or uplink data channel (e.g, PUSCH).

 

Followings are the list of DCI types and its contents defined in 38.212 - 7.3 Downlink control information.

Once a DCI data is constructed, it goes to the channel coding process and transmitted over PDCCH. This process is described in followng page.

• PDCCH Transport Process

 

 

Format 0_0

This is used for the scheduling of PUSCH in one cell. 

Format 0_1

 

This is used for the scheduling of PUSCH in one cell.

 

Field (Item)	Bits	Reference
Identifier for DCI formats	1
Carrier indicator	0 or 3
UL/SUL Indicator	0,1	0 - bit for UE not configured with SUL in the cell 1 - bit for UEs configured with SUL in the cell
Bandwidth part indicator	0,1,2	Determined by BandwidthPart-Config in higher layer message and 38.212 - Table 7.3.1.1.2-1
Frequency domain resource assignment	Variable	Variable with Resource Allocation Type
Time domain resource assignment	4	Carries the row index of the items in pusch_allocationList in RRC Number of Bit Length is determined by log(I,2), where I is the number of elements in pusch_allocationList in RRC
Frequency Hopping Flag	0,1
Modulation and coding scheme	5	38.214 - 6.1.4 (See this table)
New data indicator	1
Redundancy version	2	0,1,2,3
HARQ process number	4
1st Downlink assignment index	1,2
2nd Downlink assignment index	0,2
TPC command for scheduled PUSCH	2
SRS resource indicator	Variable	Determined by RRC Parameter SRS-SetUse
Precoding information and number of layers (TPMI)	0,2,3,4,5,6	Determined by ulTxConfig, Number of Antenna ports, PUSCH-tp, ULmaxRank
Antenna ports	2,3,4,5	Determined by PUSCH-tp, DL-DMRS-config-type, DL-DMRS-config-max-len, Rank
SRS request	2	Table 7.3.1.1.2-24
CSI request	0,1,2,3,4,5,6	Determined by ReportTriggerSize in RRC message. See Configure Aperiodic Trigger section for the details.
CBG transmission information	0,2,4,6,8	Determined by maxCodeBlockGroupPerTransportblock in RRC message
PTRS - DMRS Association	0,2	Determined by UL-PTRS-present, PUSCH-tp in RRC Message
beta_offsetr Indicator	0,2	0 - if uci-on-PUSCH.dynamic = Not Configured 2 - otherwise, see Table 7.3.1.1.2-27
DMRS Sequence Initialization	0,1	0 - if PUSCH-tp=Disabled 1 - if PUSCH-tp=Enabled
UL-SCH Indicator	1	0 - UL-SCH shall not be transmitted on the PUSCH 1 - UL-SCH shall be transmitted on the PUSCH

 

 

 

Format 1_0

 

 

This is used for the scheduling of PDSCH in one cell.

 

< DCI format 1_0 with CRC scrambled by C-RNTI >  

Field (Item)	Bits	Reference
Identifier for DCI formats	1	Always set to 1, meaning this is for DL
Frequency domain resource assignment	Variable	Variable with DL BWP N_RB
Time domain resource assignment	4	Carries the row index of the items in pdsch_allocationList in RRC
VRB-to-PRB mapping	1	According to 38.212 Table 7.3.1.1.2-33      0 : Non-Interleaved      1 : Inverleaved
Modulation and coding scheme	5	38.214  - Table 5.1.3.1-1: MCS index table 1 for PDSCH 38.214 - Table 5.1.3.1-2: MCS index table 2 for PDSCH
New data indicator	1
Redundancy version	2
HARQ process number	4
Downlink assignment index	2
TPC command for scheduled PUCCH	2
PUCCH resource indicator	3	See here , here
PDSCH-to-HARQ_feedback timing indicator	3	maps to k1={1,2,3,4,5,6,7,8}

 

< DCI format 1_0 with CRC scrambled by RA-RNTI >  

: This is used to schedule RAR (Msg2) in RACH Procedure

Field (Item)	Bits	Reference
Frequency domain resource assignment	Variable	Variable with DL BWP N_RB        indicates the size of CORESET 0
Time domain resource assignment	4	Carries the row index of the items in pdsch_allocationList in RRC
VRB-to-PRB mapping	1	According to 38.212 Table 7.3.1.1.2-33      0 : Non-Interleaved      1 : Inverleaved
Modulation and coding scheme	5	38.214  - Table 5.1.3.1-1: MCS index table 1 for PDSCH 38.214 - Table 5.1.3.1-2: MCS index table 2 for PDSCH
TB Scaling	2
Reserved	16	Reserved

 

< DCI format 1_0 with CRC scrambled by TC-RNTI >  

: This is used to schedule Contention Resolution (Msg4) in RACH Procedure

Field (Item)	Bits	Reference
Identifier for DCI formats	1	Always set to 1, meaning this is for DL
Frequency domain resource assignment	Variable	Variable with DL BWP N_RB        indicates the size of CORESET 0
Time domain resource assignment	4	Carries the row index of the items in pdsch_allocationList in RRC
VRB-to-PRB mapping	1	According to 38.212 Table 7.3.1.1.2-33      0 : Non-Interleaved      1 : Inverleaved
Modulation and coding scheme	5	38.214  - Table 5.1.3.1-1: MCS index table 1 for PDSCH 38.214 - Table 5.1.3.1-2: MCS index table 2 for PDSCH
New data indicator	1
Redundancy version	2
HARQ process number	4
Downlink assignment index	2	Reserved
TPC command for scheduled PUCCH	2
PUCCH resource indicator	3	See here , here
PDSCH-to-HARQ_feedback timing indicator	3	Row number(index) of K1

 

< DCI format 1_0 with CRC scrambled by SI-RNTI >  

: This is used to schedule SIB1 and other SIB messages

Field (Item)	Bits	Reference
Frequency domain resource assignment	Variable	Variable with DL BWP N_RB        indicates the size of CORESET 0
Time domain resource assignment	4	Carries the row index of the items. In case of DCI for SIB1, this refers to a table specified in 38.214 - Table 5.1.2.1.1-1. (NOTE 1) In case of DCI for Other SIB, this refer to  pdsch_TimeDomainAllocation in SIB
VRB-to-PRB mapping	1	According to 38.212 Table 7.3.1.1.2-33      0 : Non-Interleaved      1 : Inverleaved
Modulation and coding scheme	5	38.214  - Table 5.1.3.1-1: MCS index table 1 for PDSCH 38.214 - Table 5.1.3.1-2: MCS index table 2 for PDSCH
Redundancy Version	2
System Information Indicator	1	0 : SIB 1 1 : SI messages
Reserved	15	Reserved

 

< DCI format 1_0 with CRC scrambled by P-RNTI>  

: This is used to schedule Paging messages

Field (Item)	Bits	Reference
Short Message Indicator	2	Refer to 38.212 - Table 7.3.1.2.1-1
Short Messages	8	This field is set as reserved when 'Short Message Indicator' field is 01. Refer to 38.331 - Table 6.5-1
Frequency domain resource assignment	Variable	Variable with DL BWP N_RB        indicates the size of CORESET 0
Time domain resource assignment	4	Carries the row index of the items in pdsch_allocationList in RRC
VRB-to-PRB mapping	1	According to 38.212 Table 7.3.1.1.2-33      0 : Non-Interleaved      1 : Inverleaved
Modulation and coding scheme	5	38.214  - Table 5.1.3.1-1: MCS index table 1 for PDSCH 38.214 - Table 5.1.3.1-2: MCS index table 2 for PDSCH
TB Scaling	2
Reserved	6	Reserved

 

 

Format 1_1

 

This is used for the scheduling of PDSCH in one cell.

 

Field (Item)	Bits	Reference
Carrier indicator	0,3
Identifier for DCI formats	1	Always set to 1, indicating a DL DCI format
Bandwidth part indicator	0,1,2
Frequency domain resource assignment	Variable	Variable with Resource Allocation Type
Time domain resource assignment	4	Carries the row index of the items in pdsch_allocationList in RRC
VRB-to-PRB mapping	0,1	0 bit if only resource allocation type 0 is configured or if interleaved VRB-to-PRB mapping is not configured by high layers; 1 bit according to Table 7.3.1.1.2-33 otherwise, only applicable to resource allocation type 1
PRB bundling size indicator	0,1	0 bit if the higher layer parameter prb-BundlingType is not configured or is set to 'static' 1 bit if the higher layer parameter prb-BundlingType is set to 'dynamic'
Rate matching indicator	0,1,2	Bit size is determined by higher layer parameters rateMatchPatternGroup1 and rateMatchPatternGroup2.
ZP CSI-RS Trigger	0,1,2
Modulation and coding scheme [TB1]	5
New data indicator [TB1]	1
Redundancy version [TB1]	2
Modulation and coding scheme [TB2]	5
New data indicator [TB2]	1
Redundancy version [TB2]	2
HARQ process number	4
Downlink assignment index	0,2,4	4 bits if more than one serving cell are configured in the DL and the higher layer parameter pdsch-HARQACK-Codebook=dynamic, where the 2 MSB bits are the counter DAI and the 2 LSB bits are the total DAI; 2 bits if only one serving cell is configured in the DL and the higher layer parameter pdsch-HARQ-ACKCodebook= dynamic, where the 2 bits are the counter DAI; 0 bits otherwise.
TPC command for scheduled PUCCH	2
PUCCH resource indicator	3	See here , here
PDSCH-to-HARQ_feedback timing indicator	0,1,2,3	Row number(index) of K1 Number of bit is determined by log2(I). 'I' is the number of elements in the IE PUCCH-Config.dl-DataToUL-ACK
Antenna port(s) and number of layers	4,5,6	Determined by     dmrs Configuration Type and max Length See this summary table
Transmission configuration indication	0,3	0 bit if higher layer parameter tci-PresentInDCI is not enabled; 3 bits otherwise (See QCL page)
SRS request	2
CBG transmission information(CBGTI)	0,2,4,6,8
CBG flushing out information(CBGFI)	0,1
DMRS sequence initialization	1

 

Format 2_0

 

This is used for notifying the slot format. This DCI is scrambled by SFI_RNTI

 

Field (Item)	Bits	Reference
Identifier for DCI formats	1
Slot format indicator	Variable	Bit size is determined by RRC message here

 

Slot format indicator : a Bit string indicating Slot format indicator 1, Slot format indicator 2, …, Slot format indicator N

 

 

 

Format 2_1

 

This is used for notifying the PRB(s) and OFDM symbol(s) where UE may assume no transmission is intended for the UE.

 

Field (Item)	Bits	Reference
Identifier for DCI formats	1
Pre-emption indication	Variable

 

The size of DCI format 2_1 is configurable by higher layers up to 126 bits

 

 

Format 2_2

 

This is used for the transmission of TPC commands for PUCCH, PUSCH

 

Field (Item)	Bits	Reference
Identifier for DCI formats	1
TPC command number 1, TPC command number 2,…, TPC command number N	Variable

 

 

 

Format 2_3

 

This is used for the transmission of a group of TPC commands for SRS transmissions by one or more UEs. Along with a TPC command, a SRS request may also be transmitted.

 

Field (Item)	Bits	Reference
Identifier for DCI formats	1
block number 1, block number 2,…, block number B	Variable
SRS Request	0,2
TPC Command Number	2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference

 

 

[1] 3GPP TS 38.212 NR;Multiplexing and channel coding   

[2] 3GPP TSG RAN WG1 Meeting #92  : R1-1802117 : Discussion on DCI contents

[3] 3GPP TSG-RAN WG1 #92 : R1-1802905 : Remaining issues of the DCI contents and formats  

[4] 3GPP TSG RAN WG1 Meeting #92 : R1-1801976 : DCI Contents and Formats

[5] 3GPP TSG RAN WG1 Meeting #92 : R1-1802097 : Remaining issues on MIMO related DCI design

[6] 3GPP TSG RAN WG1 Meeting #92 : R1-1802482 : DCI contents and formats

[7] 3GPP TSG RAN WG1 Meeting #92 : R1-1802597 : Remaining issues in DCI contents and formats  

[8] 3GPP TSG RAN WG1 Meeting #92 : R1-1802209 : Remaining issues on DCI contents and formats

[9] 3GPP TSG RAN WG1 Meeting #92 : R1-1801730 : Open issues on DCI contents and formats

[10] 3GPP TSG RAN WG1 Meeting #92 : R1-1801624 : Remaining issues on DCI content