3GPP 38.300 v19.3.0 — the document's own text
5.2.3 Physical downlink control channels
Taught in 2. The six working groups and the line between them (TSG RAN — the group that specifies the radio, overview), 2. The six groups, and what each one worries about (TSG RAN — the group that specifies the radio, quick start).
The Physical Downlink Control Channel (PDCCH) can be used to schedule DL transmissions on PDSCH and UL transmissions on PUSCH, where the Downlink Control Information (DCI) on PDCCH includes:
- Downlink assignments containing at least modulation and coding format, resource allocation, and hybrid-ARQ information related to DL-SCH;
- Uplink scheduling grants containing at least modulation and coding format, resource allocation, and hybrid-ARQ information related to UL-SCH.
In addition to scheduling, PDCCH can be used to for:
- Activation and deactivation of configured PUSCH transmission with configured grant;
- Activation and deactivation of PDSCH semi-persistent transmission;
- Notifying one or more UEs of the slot format;
- Notifying one or more UEs of the PRB(s) and OFDM symbol(s) where the UE may assume no transmission is intended for the UE;
- Transmission of TPC commands for PUCCH and PUSCH;
- Transmission of one or more TPC commands for SRS transmissions by one or more UEs;
- Switching a UE's active bandwidth part;
- Initiating a random access procedure;
- Indicating the UE(s) to monitor the PDCCH during the next occurrence of the DRX on-duration;
- In IAB context, indicating the availability for soft symbols of an IAB-DU;
- Triggering one shot HARQ-ACK codebook feedback;
- For operation with shared spectrum channel access:
- Triggering search space set group switching;
- Indicating one or more UEs about the available RB sets and channel occupancy time duration;
- Indicating downlink feedback information for configured grant PUSCH (CG-DFI).
A UE monitors a set of PDCCH candidates in the configured monitoring occasions in one or more configured COntrol REsource SETs (CORESETs) according to the corresponding search space configurations.
A CORESET consists of a set of PRBs with a time duration of 1 to 3 OFDM symbols. The resource units Resource Element Groups (REGs) and Control Channel Elements (CCEs) are defined within a CORESET with each CCE consisting a set of REGs. Control channels are formed by aggregation of CCE. Different code rates for the control channels are realized by aggregating different number of CCE. Interleaved and non-interleaved CCE-to-REG mapping are supported in a CORESET.
The PDCCH repetition is operated by using two search spaces which are explicitly linked by configuration provided by the RRC layer, and are associated with corresponding CORESETs. For PDCCH repetition, two linked search spaces are configured with the same number of candidates, and two PDCCH candidates in two search spaces are linked with the same candidate index. When PDCCH repetition is scheduled to a UE, an intra-slot repetition is allowed and each repetition has the same number of CCEs and coded bits, and corresponds to the same DCI payload.
Polar coding is used for PDCCH.
Each resource element group carrying PDCCH carries its own DMRS.
QPSK modulation is used for PDCCH.