Description
DCP is a critical physical layer signaling mechanism in 3GPP New Radio (NR). It refers to a Downlink Control Information (DCI) format whose Cyclic Redundancy Check (CRC) bits are scrambled (i.e., masked) by the Paging RNTI (PS-RNTI). The PS-RNTI is a fixed, predefined identifier (value: 0xFFFE) known to all User Equipments (UEs). This scrambling operation is fundamental to the paging procedure. When a UE is in a low-power state like RRC_IDLE or RRC_INACTIVE, it does not maintain a continuous connection to the network. Instead, it periodically wakes up to monitor specific time-frequency resources known as Paging Occasions (POs) within a Paging Frame (PF). During these POs, the UE blindly decodes the Physical Downlink Control Channel (PDCCH) for DCIs. It attempts to descramble the CRC of any detected DCI using the PS-RNTI. If the descrambling is successful, it confirms that the DCI is a DCP intended for paging. The DCP itself does not carry the paging message content. Instead, it contains scheduling assignment information, such as the modulation and coding scheme, resource block allocation, and transport format. This scheduling information points the UE to the specific resources on the Physical Downlink Shared Channel (PDSCH) where the actual paging message, encapsulated in a Paging MAC Control Element or RRC Paging message, is transmitted. The UE then decodes the PDSCH at the indicated location to receive the full paging information, which may contain its identity if it is being paged for an incoming call, SMS, or other mobile-terminated service. This two-step process (DCP on PDCCH, then message on PDSCH) is highly efficient. It allows the network to page multiple UEs simultaneously within the same paging message while enabling UEs to perform minimal processing—only decoding the full PDSCH payload if the DCP indicates a paging transmission is present. The specifications governing DCP, such as TS 38.212 for the physical channel processing and TS 38.331 for RRC procedures, detail the exact DCI format (e.g., DCI format 1_0) used and the associated scrambling and decoding processes.
Purpose & Motivation
The primary purpose of DCP is to enable efficient, network-initiated wake-up of UEs in power-saving states for mobile-terminated services. In cellular networks, a UE cannot be contacted unless the network knows its approximate location and can signal it. When a UE is idle, it conserves battery by turning off its receiver most of the time. The network groups UEs into paging groups based on their identifiers and configures them with a Discontinuous Reception (DRX) cycle. The DCP mechanism solves the problem of how to alert a specific UE within a group without requiring all UEs to constantly listen to the channel. By using a common PS-RNTI, any UE monitoring a given PO can efficiently identify control information meant for its paging group. The scheduling information within the DCP then directs only the UEs that need to decode the subsequent paging message, minimizing unnecessary PDSCH processing for UEs not being paged. This design is a direct evolution from LTE's paging procedure but is adapted for the more flexible NR frame structure. It addresses the fundamental trade-off between UE battery life and network accessibility. Without such a targeted signaling method, UEs would either need to remain in a connected state (draining battery) or the network would have to broadcast full paging messages more frequently (wasting radio resources). DCP provides the precise, low-overhead trigger that balances these demands.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (126 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the DCP (Downlink Control Information with CRC scrambled by PS-RNTI) function was newly introduced for power saving purposes in Multi-Radio Dual Connectivity (MR-DC) scenarios. Specifically, the UE can be configured to monitor for DCP on the PCell if the Master Node is a gNB (for NE-DC and NR-DC) and/or on the PSCell if the Secondary Node is a gNB. This allows the network to manage UE power consumption more efficiently within the dual connectivity framework.
- PSCell information for LI purposes TS 37.340CR0107
- Correction of the references to the GTP tunnel endpoint information TS 37.340CR0138
- Correction on sending Failure Information via SRB3 TS 37.340CR0159
- Slicing assistance information TS 38.300CR0024
- Corrections to Unified Access Control TS 38.300CR0036
- System Information Handling in TS38.300 TS 38.300CR0071
+ 38 more changes
In Release 16, the DCP function was enhanced with specific corrections and clarifications for operation in Multi-RAT Dual Connectivity (MR-DC) scenarios. These included a correction on prioritization between DCP and RAR to C-RNTI for Contention-Free Random Access (CFRA) used in Beam Failure Recovery (BFR), addressing potential conflicts in the scheduling of these control signals. Furthermore, the release clarified the initial state of elements controlled by MAC CE and non-numerical K1 values related to DCP monitoring, refining the UE's behavior when configured for power saving on either the PCell or PSCell.
- CR for 37.340 on power control for NR_DC TS 37.340CR0235
- Corrections on AQP for notification control TS 37.340CR0242
- Correction on prioritization between DCP and RAR to C-RNTI for CFRA BFR TS 38.300CR0295
- Corrections on AQP for notification control TS 38.300CR0328
- Correction on prioritization between DCP and RAR to C-RNTI for CFRA BFR – Option 2 TS 38.321CR0794
- Clarification on the initial state of elements controlled by MAC CE and non-numerical K1 value TS 38.321CR1209
+ 7 more changes
In Release 17, a correction was made to the DCP function regarding CSI reporting. This specific enhancement, detailed in a Change Request titled "Correction on CSI reporting for DCP function," refined the operation of Downlink Control Information scrambled by the PS-RNTI to ensure proper Channel State Information reporting procedures.
- 38.331 CR for introduction of MBS PDSCH FDM capabilities TS 38.331CR3483
- Corrections to UE History Information in MR-DC TS 37.340CR0332
- Xn-U Address Information delivery in CPAC TS 37.340CR0362
- Correction of UE History Information for CHO TS 38.300CR0607
- Clarification on slice group information provided by NAS TS 38.300CR0610
- Corrections on CRS-IM network assistance information TS 38.331CR3481
+ 16 more changes
In Release 18, the DCP function was enhanced to support power saving in Multi-RAT Dual Connectivity (MR-DC) scenarios where the Secondary Node is a gNB. Specifically, the specifications clarified that a UE can be configured to monitor for DCP on the PSCell for power saving purposes. This builds upon the existing framework where DCP could already be monitored on the PCell when the Master Node is a gNB.
- Introducing support for Network-Controlled Repeaters to 38.300 TS 38.300CR0685
- Introduction of MIMO evolution for Downlink and Uplink TS 38.300CR0742
- Introduction of support for Network Controlled Repeaters TS 38.321CR1554
- GNSS LOS/NLOS posSIB broadcast assistance information [GNSS LOS/NLOS] TS 38.331CR4109
- Introduction of Network Controlled Repeaters in RRC spec TS 38.331CR4162
- Downlink positioning support and posSIB request for L2 UE-to-network remote UE [PosL2RemoteUE] TS 38.331CR4066
+ 28 more changes
In Release 19, the DCP (Downlink Control Information with CRC scrambled by PS-RNTI) function was enhanced to support power saving in Multi-RAT Dual Connectivity (MR-DC) scenarios. Specifically, the UE can now be configured to monitor DCP on the PSCell when the Secondary Node is a gNB, in addition to the existing configuration for monitoring on the PCell when the Master Node is a gNB. This allows for more granular power saving control across both cell groups.
- Introduction of control parameters for on-demand posSIB request [OdPosSIB_Req] TS 38.300CR1009
- Support Aerial UE Flight Information Reporting TS 38.300CR1031
- Introduction of common PDCCH repetition (Rel-19 NTN) for TN [Common_PDCCH_rep_TN] TS 38.300CR1058
- Introduction of control parameters for on-demand posSIB request [OdPosSIB_Req] TS 38.331CR5406
- Introduction of UE assistance information for cell DTX/DRX [UAI_cellDTRX] TS 38.331CR5474
- Correction on multi-modality, uplink rate control and available bit rate monitoring TS 37.340CR0430
+ 7 more changes
Explore further
Broader topics and technologies where DCP plays a role.
Defining Specifications
3GPP specifications that define or reference DCP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 37.340 vj00 | Multi-Connectivity Operation Overview | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.321 vj00 | NR MAC Protocol Specification | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TR 38.869 vi00 | Study on low-power wake up signal and receiver for NR | Rel-18 |