The control information carried on the PDCCH is called DCI. The size of the DCI payload may vary with scenarios, and different DCI formats may be used accordingly. Based on DCI contents and functions, eight DCI formats used in three types of scenarios are defined in section 7.3.1 “DCI formats” in 3GPP TS 38.212 V15.6.0.
Table-1 DCI formats.
| Type of Scenario | DCI Format | Function | Carried Information |
|---|---|---|---|
| Physical uplink shared channel (PUSCH) scheduling indication | Format 0_0 | DCI of this format is used to indicate PUSCH scheduling and fallback, and is used in scenarios such as waveform change and state switching. | Scheduling resource position, frequency hopping indication, modulation and coding scheme (MCS), HARQ indicator, transmit power control (TPC), and others |
| Format 0_1 | DCI of this format is used to indicate PUSCH scheduling. | Carrier/bandwidth part (BWP) indication, scheduling resource position, frequency hopping indication, MCS, HARQ indicator, sounding reference signal (SRS) resource indication, precoding information, antenna port, scheduling request indicator (SRI), channel state information (CSI) request, code block group (CBG) transmission, TPC, waveform indication, and others | |
| Physical downlink shared channel (PDSCH) scheduling indication | Format 1_0 | DCI of this format is used to indicate PDSCH scheduling and fallback, and is used in scenarios such as common message scheduling (for example, paging and RMSI scheduling), and state switching (for example, BWP switching). (RMSI is short for Remaining Minimum SI.) | Scheduling resource position, MCS, HARQ indicator, TPC, PUCCH resource position, and others |
| Format 1_1 | DCI of this format is used to indicate PDSCH scheduling. | Carrier/BWP indication, scheduling resource position, MCS, HARQ indicator, TPC, CSI reference signal (CSI-RS) triggering, PUCCH resource position, precoding information, antenna port, CBG transmission, and others | |
| Other scenarios | Format 2_0 | DCI of this format is used to indicate the slot format indicator (SFI). | SFI information indication |
| Format 2_1 | DCI of this format is used to indicate the physical resource blocks (PRBs) and OFDM symbols to which UEs do not map data. | Pre-emption indicator (PI) indication | |
| Format 2_2 | DCI of this format is used to indicate the TPC commands for PUCCH and PUSCH. | TPC commands for PUCCH and PUSCH | |
| Format 2_3 | DCI of this format is used to indicate the TPC commands for SRS. | TPC commands for SRS |
DCI with different contents is distinguished by using different RNTIs for scrambling. For details about DCI formats and DCI resource allocation, see section 7.3.1 “DCI formats” in 3GPP TS 38.212. The focus of this document is placed on the overall PDCCH resource configuration.
| Type | DCI Format | RNTI and Corresponding DCI Content |
|---|---|---|
| PUSCH scheduling indication | Format 0_0 | Cell RNTI (C-RNTI): used for PUSCH scheduling.Temporary C-RNTI (TC-RNTI): used for Msg3 scheduling during random access. |
| Format 0_1 | Cell RNTI (C-RNTI): used for PUSCH scheduling. | |
| PDSCH scheduling indication | Format 1_0 | C-RNTI: used for PDSCH scheduling.Paging RNTI (P-RNTI): used for paging message scheduling.System information RNTI (SI-RNTI): used for SI scheduling.Random access RNTI (RA-RNTI): used for random access response (RAR) scheduling during random access.TC-RNTI: used for Msg4 scheduling during random access. |
| Format 1_1 | C-RNTI: used for PDSCH scheduling. | |
| Other scenarios | Format 2_0 | SFI-RNTI: used for slot format information. |
| Format 2_1 | Interruption RNTI (INT-RNTI): used for pre-emption resource occupation information. | |
| Format 2_2 | TPC-PUSCH-RNTI: used for the TPC commands for PUSCH.TPC-PUCCH-RNTI: used for the TPC commands for PUCCH. | |
| Format 2_3 | TPC-SRS-RNTI: used for the TPC commands for SRS. |
A UE needs to demodulate the PDCCH to obtain the DCI before it can demodulate its PDSCH (including broadcast messages, paging, UE data, and others) at the corresponding resource position. UEs do not know the specific position of a PDCCH. How a UE demodulates the PDCCH to obtain the DCI is a question that involves the CORESET and search space.