LTE DCI
LTE DCI has a lot more additional information in it. In addition to resource allocation, it can carry Power Control Command, CSI Report Request or CQI Report Request etc.
L1 signaling is done by DCI and Up to 8 DCIs can be configured in the PDCCH. These DCIs can have 6 formats : 1 format for UL scheduling, 2 formats for Non-MIMO DL scheduling, 1 format for MIMO DL Scheduling and 2 formats for UL power control.
DCI has various formats for the information sent to define resource allocations. The DCI formats defined in LTE are as follows.
| Usage |
Major Contents |
|
| Format 0 |
UL Grant. Resource Allocation for UL Data |
RB Assignment,TPC,PUSCH Hopping Flag |
| Format 1 |
DL Assignment for SISO |
RB Assignment,TPC, HARQ |
| Format 1A |
DL Assignment for SISO (compact) |
RB Assignment,TPC, HARQ |
| Format 1B |
DL Assignment for MIMO with Rank 1 |
RB Assignment,TPC, HARQ,TPMI, PMI |
| Format 1C |
DL Assignment for SISO (minimum size) |
RB Assignment |
| Format 1D |
DL Assignment for Multi User MIMO |
RB Assignment,TPC, HARQ,TPMI,DL Power Offset |
| Format 2 |
DL Assignment for Closed Loop MIMO | RB Assignment,TPC, HARQ, Precoding Information |
| Format 2A |
DL Assignment for Open Loop MIMO | RB Assignment,TPC, HARQ, Precoding Information |
| Format 2B |
DL Assignment for TM8 (Dual Layer Beamforming) | RB Assignment,TPC, HARQ, Precoding Information |
| Format 2C |
DL Assignment for TM9 | RB Assignment,TPC, HARQ, Precoding Information |
| Format 3 |
TPC Commands for PUCCH and PUSCH with 2 bit power adjustment | Power Control Only |
| Format 3A |
TPC Commands for PUCCH and PUSCH with 1 bit power adjustment | Power Control Only |
| Format 4 |
UL Assignment for UL MIMO (up to 4 layers) | RB Assignment,TPC, HARQ, Precoding Information |
There are two major factors to determine a DCI format for a specific situation as follows :
i) RNTI Type
ii) Transmission Mode
< 38.213-v14.6.0 Table 7.1-1: PDCCH and PDSCH configured by SI-RNTI >
| DCI format |
Search Space |
Transmission scheme of PDSCH corresponding to PDCCH |
| DCI format 1C |
Common |
If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity . |
| DCI format 1A |
Common |
If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity . |
< 38.213-v14.6.0 Table 7.1-2: PDCCH and PDSCH configured by P-RNTI >
| DCI format |
Search Space |
Transmission scheme of PDSCH corresponding to PDCCH |
| DCI format 1C | Common | If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity |
| DCI format 1A | Common | If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
< 38.213-v14.6.0 Table 7.1-3: PDCCH and PDSCH configured by RA-RNTI >
| DCI format |
Search Space |
Transmission scheme of PDSCH corresponding to PDCCH |
| DCI format 1C | Common | If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
| DCI format 1A | Common | If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
< 38.213-v14.6.0 Table 7.1-5: PDCCH and PDSCH configured by C-RNTI>
| Transmission mode |
DCI format |
Search Space |
Transmission scheme of PDSCH corresponding to PDCCH |
| Mode 1 |
DCI format 1A |
Common and UE specific by C-RNTI |
Single-antenna port, port 0 |
| DCI format 1 |
UE specific by C-RNTI |
Single-antenna port, port 0 |
|
| Mode 2 |
DCI format 1A |
Common and UE specific by C-RNTI |
Transmit Diversity |
| DCI format 1 |
UE specific by C-RNTI |
Transmit Diversity |
|
| Mode 3 |
DCI format 1A |
Common and UE specific by C-RNTI |
Transmit Diversity |
| DCI format 2A |
UE specific by C-RNTI |
Large delay CDD or Transmit Diversity |
|
| Mode 4 |
DCI format 1A |
Common and UE specific by C-RNTI |
Transmit Diversity |
| DCI format 2 |
UE specific by C-RNTI |
Closed-loop multiplexing or Transmit Diversity |
|
| Mode 5 |
DCI format 1A |
Common and UE specific by C-RNTI |
Transmit Diversity |
| DCI format 1D |
UE specific by C-RNTI |
Multi-user MIMO |
|
| Mode 6 |
DCI format 1A |
Common and UE specific by C-RNTI |
Transmit Diversity |
| DCI format 1B |
UE specific by C-RNTI |
Closed-loop multiplexing using a single transmission layer |
|
| Mode 7 |
DCI format 1A |
Common and UE specific by C-RNTI |
If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
| DCI format 1 |
UE specific by C-RNTI |
Single-antenna port, port 5 |
|
| Mode 8 |
DCI format 1A |
Common and UE specific by C-RNTI |
If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
| DCI format 2B |
UE specific by C-RNTI |
Dual layer transmission, port 7 and 8 or single-antenna port, port 7 or 8 |
|
| Mode 9 |
DCI format 1A |
Common and UE specific by C-RNTI |
Non-MBSFN subframe: If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity |
| DCI format 2C |
UE specific by C-RNTI |
Transmit diversity, port 7-8, or dual layer transmission port 7-8 , if UE is configured with higher layer parameter semiOpenLoop, up to 8 layer transmission, ports 7-14 otherwise; or single-antenna port, port 7, 8, 11, or 13 if UE is configured with higher layer parameter dmrs-tableAlt, single-antenna port, port 7 or 8 otherwise |
|
| Mode 10 |
DCI format 1A |
Common and UE specific by C-RNTI |
Non-MBSFN subframe: If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity |
| DCI format 2D |
UE specific by C-RNTI |
Transmit diversity, port 7-8, or dual layer transmission port 7-8 , if UE is configured with higher layer parameter semiOpenLoop, up to 8 layer transmission, ports 7-14 otherwise; or single-antenna port, port 7, 8, 11, or 13 if UE is configured with higher layer parameter dmrs-tableAlt, single-antenna port, port 7 or 8 otherwise |
< 38.213-v14.6.0 Table 7.1-7: PDCCH and PDSCH configured by Temporary C-RNTI>
| DCI format |
Search Space |
Transmission scheme of PDSCH corresponding to PDCCH |
| DCI format 1A | Common and UE specific by C-RNTI | If the number of PBCH antenna port is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
| DCI format 1 | UE specific by C-RNTI | If the number of PBCH antenna port is one, Single-antenna port, port 0 is used , otherwise Transmit diversity |
Any relations between DCI format and Layer 3 signaling message ?
Yes, there is a relationship. You have to know which DCI format is required for which RRC message. Following tables from 3GPP 36.321 shows the relationship between RNTI and logical channel and you would know which RRC message is carried by which logical channel. So with two step induction, you will figure out the link between RRC message and it's corresponding DCI format.
For example, if you see the "Security Mode Command" message of section 6.2.2 of 36.331, it says
Signalling radio bearer: SRB1
RLC-SAP: AM
Logical channel: DCCH
Direction: UE to E-UTRAN
If you see the table, you would see this message is using C-RNTI. and you will figure out the possible candiates from table 7.1-5 of 36.213 and if you would have detailed information of the transmission mode, you can pinpoint out exactly which DCI format you have to use for this message for a specific case. Assuming TM mode in this case is TM1 and scheduling is dynamic scheduling, if you see Table 7.1-2 you will figure out that this is using C-RNTI. With this RNTI Type and TM mode, if you see table 7.1-5, this case use DCI Format 1 or DCI Format 1A.