Description
The Physical Downlink Shared Channel (PDSCH) is a fundamental downlink transport channel in 3GPP radio access technologies, including UMTS, LTE, and NR. It carries all user-plane data (such as internet packets) and most control-plane information (like RRC messages and system information blocks) from the base station (eNodeB in LTE, gNB in NR) to the user equipment (UE). The channel is 'shared' because its time-frequency resources are dynamically allocated among multiple UEs by the base station scheduler in each transmission time interval (TTI), based on factors like channel quality, QoS requirements, and fairness.
In operation, the PDSCH utilizes Orthogonal Frequency Division Multiple Access (OFDMA) in LTE and cyclic prefix OFDM (CP-OFDM) in NR. The scheduler determines which resource blocks (RBs) are assigned to which UE for each subframe (LTE) or slot (NR). The UE must first decode the Physical Downlink Control Channel (PDCCH) to find its Downlink Control Information (DCI), which contains the scheduling assignment specifying the RBs, modulation and coding scheme (MCS), and other parameters for its PDSCH reception. The data on PDSCH is then demodulated and decoded using the indicated parameters.
The PDSCH's performance is critical for overall system capacity and data rates. It supports advanced features like Multiple Input Multiple Output (MIMO) transmission (e.g., spatial multiplexing, beamforming), hybrid automatic repeat request (HARQ) for error correction, and adaptive modulation and coding (AMC) to match the transmission to the radio channel conditions. In NR, the PDSCH design was enhanced with more flexible numerology (subcarrier spacing), mini-slot scheduling for low latency, and support for diverse use cases from enhanced mobile broadband (eMBB) to ultra-reliable low-latency communications (URLLC).
Purpose & Motivation
The PDSCH was created to provide an efficient, flexible, and high-capacity mechanism for transmitting downlink data in packet-switched cellular systems. Earlier systems like GSM used dedicated timeslots for each user, which was inefficient for bursty data traffic. The shared channel concept, introduced with UMTS and refined in LTE and NR, allows statistical multiplexing of multiple users' data over a common pool of radio resources, dramatically improving spectral efficiency.
It solves the problem of how to dynamically allocate limited radio bandwidth to many users with varying and unpredictable data demands. By being scheduler-controlled, the PDSCH enables the network to prioritize traffic, manage interference, and adapt to fast-changing radio conditions. The evolution from a dedicated to a shared channel model was motivated by the need to support broadband internet access and multimedia services, requiring much higher data rates and more efficient resource utilization than circuit-switched or early packet-switched designs could offer.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (380 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the PDSCH saw the introduction of support for higher order modulation with Downlink 1024QAM, enhancing peak data rates. The release also included corrections and clarifications to PDSCH procedures, specifically addressing the mapping from virtual to physical resource blocks and the resource allocation when scheduled by PDCCH in Type 0 common search space. Furthermore, enhancements were made to support advanced UE capabilities for FD-MIMO processing within EN-DC scenarios.
- Introduction of Downlink 1024QAM into 36.201 TS 36.201CR0025
- Advanced CSI CBSR CBSR related capability for FD-MIMO TS 36.306CR1593
- Clarification on CRC attachment for DL-SCH and PCH transport channels in NB-IoT TS 36.212CR0285
- Correction on the interpretation of HARQ-ACK bitmap for FeLAA in 36.212 TS 36.212CR0297
- 36.300 CR on Correction of Physical Layer Resource to Cell Resource TS 36.300CR1211
- Minor corrections to services provided by physical layer TS 36.302CR1195
+ 48 more changes
In Release 16, key PDSCH enhancements focused on improving Downlink MIMO efficiency and supporting Ultra-Reliable Low-Latency Communications (URLLC) through specific physical layer procedures. These included the introduction of new UE capabilities and reference signal configurations for enhanced MIMO performance. Additionally, the release introduced mechanisms for operation in shared spectrum, impacting channel access and scheduling for the downlink shared channel.
- Introduction of Rel-16 DL MIMO EE features in 36.212 TS 36.212CR0330
- Introduction of UE capabilities for DL MIMO efficiency enhancement TS 36.306CR1770
- Introduction of Physical Layer Enhancements for URLLC TS 38.202CR0012
- Introduction of MIMO enhancements TS 38.202CR0013
- Introduction of MIMO enhancements TS 38.211CR0028
- Introduction of Physical Layer Enhancements for NR URLLC TS 38.212CR0026
+ 92 more changes
In Release 17, the PDSCH function was enhanced with further MIMO improvements and expanded support for advanced reception scenarios. Key updates included corrections and clarifications for the simultaneous reception of specific channels and enhancements to HARQ processes, including support for up to 32 processes in certain frequency ranges. Additionally, refinements were made to Downlink Control Information (DCI) handling for non-terrestrial networks and multicast HARQ-ACK codebooks.
- Introduction of MIMO enhancements TS 38.211CR0080
- Introduction of Further enhancements on MIMO for NR TS 38.212CR0089
- Introduction of further enhancements on MIMO for NR TS 38.213CR0277
- Introduction of further enhancements on MIMO for NR TS 38.214CR0228
- Correction on simultaneous reception of SDT and other channels in TS 38.202 TS 38.202CR0026
- Corrections to MIMO enhancements TS 38.211CR0091
+ 96 more changes
In Release 18, the PDSCH saw specific advancements primarily within the broader scope of MIMO evolution for downlink, as indicated by the multiple CRs focused on MIMO enhancements. These included new specification support for MIMO enhancements on CSI and introduced multi-cell PDSCH scheduling. Furthermore, the release incorporated corrections and refinements to these MIMO enhancements, ensuring improved performance and reliability.
- Introduction of sidelink channel access procedures for Rel-18 NR sidelink evolution TS 38.201CR0003
- Release 18 TS38.202 Editor CR for MIMO TS 38.202CR0027
- Introduction of MIMO evolution for downlink and uplink TS 38.211CR0110
- Introduction of Rel-18 MIMO Evolution for Downlink and Uplink TS 38.212CR0145
- Introduction of MIMO Evolution for Downlink and Uplink TS 38.213CR0504
- Introduction of multiplexing in a PUSCH with repetitions HARQ-ACK associated with DL assignments received after an UL grant for the PUSCH [HARQ-ACK MUX on PUSCH] TS 38.213CR0568
+ 84 more changes
In Release 19, specific enhancements for the PDSCH included corrections to its resource mapping procedure. Furthermore, the release introduced support for 32 HARQ process numbers, increasing scheduling flexibility. These updates were part of broader MIMO Phase 5 and HARQ process number introductions noted in the Change Requests.
- CR to TS 38.176-2: restriction of 7MHz channel bandwidth introduction TS 38.176CR0087
- Introduction of NR MIMO Phase5 TS 38.211CR0153
- Introduction of Rel-19 NR MIMO Phase 5 TS 38.212CR0220
- Introduction of 32 HARQ process numbers in Rel-19 [TN32HARQ] TS 38.212CR0222
- Introduction of NR MIMO Phase 5 TS 38.213CR0710
- Introduction of PDCCH repetitions for Type0-PDCCH CSS set in TNs [Common_PDCCH_Rep_TN] TS 38.213CR0748
+ 30 more changes
Explore further
Broader topics and technologies where PDSCH plays a role.
Defining Specifications
3GPP specifications that define or reference PDSCH, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 25.202 vj00 | 7.68Mcps TDD Option Technical Specification | Rel-19 |
| TS 25.211 vj00 | UTRA FDD Layer 1: Transport & Physical Channels | Rel-19 |
| TS 25.213 vj00 | UTRA FDD Spreading and Modulation | Rel-19 |
| TS 25.214 vj00 | UTRA FDD Physical Layer Procedures | Rel-19 |
| TS 25.221 vj00 | UTRA TDD Physical Layer Specification | Rel-19 |
| TS 25.224 vj00 | UTRA TDD Physical Layer Procedures | Rel-19 |
| TS 25.225 vj00 | UTRA TDD Physical Layer Measurements | Rel-19 |
| TS 25.331 vj00 | UTRAN RRC Protocol Specification | Rel-19 |
| TS 25.423 vj00 | UTRAN RNSAP Specification | Rel-19 |
| TS 25.430 vj00 | Introduction to Iub Interface Specifications | Rel-19 |
| TS 25.433 vj00 | Node B Application Part (NBAP) Protocol | Rel-19 |
| TS 25.435 vj00 | UTRAN Iub Interface User Plane Protocols | Rel-19 |
| TR 25.931 vj00 | UTRAN Signalling Procedures Examples | Rel-19 |
| TS 36.104 vj10 | Base Station (BS) radio transmission and reception | Rel-19 |
| TS 36.116 vj00 | E-UTRA Relay RF Requirements | Rel-19 |
| TS 36.117 vj00 | E-UTRA Relay RF Test Methods & Requirements | Rel-19 |
| TS 36.133 vj20 | E-UTRA RRM Requirements | Rel-19 |
| TS 36.141 vj00 | E-UTRA BS Conformance Testing | Rel-19 |
| TS 36.201 vj00 | LTE Physical Layer General Description | Rel-19 |
| TS 36.211 vj10 | LTE Physical Layer Specification | Rel-19 |
| TS 36.212 vj10 | LTE Multiplexing and Channel Coding | Rel-19 |
| TS 36.213 vj10 | LTE Physical Layer Procedures | Rel-19 |
| TS 36.216 vj00 | LTE Relay Node Physical Layer | Rel-19 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.302 vj00 | E-UTRA Physical Layer Services | Rel-19 |
| TS 36.306 vj00 | E-UTRA UE Radio Access Capability Parameters | Rel-19 |
| TS 36.747 ve00 | Enhanced CRS and SU-MIMO IM Performance Requirements | Rel-14 |
| TS 36.790 vf00 | LAA/eLAA for CBRS 3.5GHz Band in US | Rel-15 |
| TS 36.825 vd00 | Study on Additional LTE TDD Configurations | Rel-13 |
| TS 36.855 vd00 | E-UTRA Positioning Enhancements Study | Rel-13 |
| TS 36.863 vc00 | CRS Interference Mitigation for Homogeneous Networks | Rel-12 |
| TS 36.867 vd00 | LTE DL 4 Rx Antenna Port Study TR | Rel-13 |
| TR 36.976 vj00 | LTE-based 5G Terrestrial Broadcast Overview | Rel-19 |
| TS 37.107 vj00 | RF Requirements for LAA and NR-U Base Stations | Rel-19 |
| TS 37.857 vd10 | Study on Indoor Positioning Enhancements | Rel-13 |
| TR 37.901 vf10 | UE Application Layer Data Throughput Performance | Rel-15 |
| TR 37.911 vj00 | 3GPP 5G NTN Self-Evaluation Report | Rel-19 |
| TS 38.133 vj20 | 5G UE Radio Requirements for RRC_IDLE Mobility | Rel-19 |
| TS 38.174 vj10 | NR Integrated Access and Backhaul Radio Spec | Rel-19 |
| TS 38.176 vj20 | IAB Conformance Testing Specification | Rel-19 |
| TS 38.201 vj00 | NR Physical Layer General Description | Rel-19 |
| TS 38.202 vj00 | 5G NR Physical Layer Services | Rel-19 |
| TS 38.211 vj10 | NR Physical Channels and Modulation | Rel-19 |
| TS 38.212 vj10 | NR Multiplexing and Channel Coding | Rel-19 |
| TS 38.213 vj10 | NR Physical Layer Control Procedures | Rel-19 |
| TS 38.214 vj10 | NR Physical Layer Procedures for Data | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.521 vj20 | NR Physical Layer UE Conformance Testing | Rel-19 |
| TS 38.522 vj11 | UE Conformance Test Applicability Statement | Rel-19 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |
| TS 38.551 vi30 | User Equipment (UE) Multiple Input Multiple Output (MIMO) Over-the-Air (OTA) performance | Rel-18 |
| TR 38.808 vh00 | Study on NR above 52.6 GHz to 71 GHz | Rel-17 |
| TS 38.824 vg00 | NR URLLC Physical Layer Enhancements Study | Rel-16 |
| TR 38.830 vh00 | NR Coverage Enhancements Study | Rel-17 |
| TS 38.831 vg10 | UE RF Requirements for FR2 Enhancements | Rel-16 |
| TR 38.838 vh00 | Study on XR Evaluations for NR | Rel-17 |
| TR 38.869 vi00 | Study on low-power wake up signal and receiver for NR | Rel-18 |
| TR 38.878 vi40 | Technical Report on Advanced Receiver for MU-MIMO | Rel-18 |
| TR 38.889 vg00 | NR-based access to unlicensed spectrum study | Rel-16 |
| TR 38.903 vj00 | Test Tolerances & Measurement Uncertainties | Rel-19 |
| TS 45.820 vd10 | CIoT for Internet of Things | Rel-13 |