Description
The Physical Sidelink Shared Channel (PSSCH) is a key physical layer channel defined in 3GPP specifications for sidelink (SL) communication, introduced in LTE Release 12 and continued in 5G NR. Sidelink refers to direct communication between User Equipments (UEs) without the data passing through a base station (eNodeB/gNB) or the core network. The PSSCH is the primary channel used to transport user data (transport blocks) and associated sidelink control information (SCI) between UEs in proximity. It operates in the uplink spectrum for LTE-based sidelink (Mode 3 and 4) and in dedicated or shared spectra for NR sidelink.
The PSSCH transmission involves several physical layer procedures. A transmitting UE first sends Sidelink Control Information (SCI) on the Physical Sidelink Control Channel (PSCCH), which is typically mapped to resources adjacent or nearby to the PSSCH resources. This SCI carries crucial information for the receiving UE to decode the subsequent PSSCH transmission, including resource allocation, modulation and coding scheme (MCS), group destination ID, and timing information. The actual user data is then transmitted on the PSSCH using the resources and parameters indicated by the SCI. The channel utilizes similar modulation schemes (QPSK, 16QAM, 64QAM, 256QAM in NR) and coding (Turbo codes in LTE, LDPC in NR) as other shared channels.
In terms of resource allocation, two main modes are defined for LTE V2X: Mode 3 (scheduled) where the eNodeB allocates sidelink resources, and Mode 4 (autonomous) where the UE autonomously selects resources using a sensing and reservation protocol. NR sidelink introduces more advanced modes with greater flexibility. The PSSCH is fundamental for applications requiring low latency and high reliability, such as vehicle platooning, autonomous driving coordination, and public safety D2D communication. Its design includes features for handling high mobility, half-duplex constraints (a UE cannot transmit and receive on the same frequency simultaneously), and interference management in a distributed environment.
Purpose & Motivation
PSSCH was created to support direct device-to-device communication, a capability essential for new use cases beyond traditional cellular communication. The initial driver in LTE Release 12 was Proximity Services (ProSe) for public safety, allowing first responders to communicate directly when network infrastructure is damaged or unavailable. This addressed a critical limitation of conventional cellular networks, which rely entirely on base station coverage.
The motivation expanded significantly with the introduction of Vehicle-to-Everything (V2X) communication in LTE Release 14. Existing vehicular communication standards like IEEE 802.11p (DSRC) had limitations in scalability, coverage, and integration with cellular networks. PSSCH, as part of the 3GPP V2X standard, was designed to provide a more robust, high-capacity, and network-managed alternative for direct vehicle communication. It solves problems related to high-speed mobility, dense scenarios, and quality of service by leveraging the cellular spectrum and physical layer design. The creation of PSSCH enabled low-latency broadcast, groupcast, and unicast communication between vehicles, pedestrians, and infrastructure, forming the foundation for advanced driving safety and autonomous vehicle coordination.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (71 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-12, normative work from Rel-15.
In Release 15, specific technical corrections were made for V2X sidelink communication, including adjustments to the Modulation and Coding Scheme (MCS) for the PSSCH as detailed in TS 36.302. Furthermore, the release defined new UE maximum output power requirements for modulation and channel bandwidth specifically for V2X Communication. These updates provided essential clarifications and corrections to ensure reliable physical layer operation for sidelink in V2X scenarios.
- Clarification on CRC attachment for DL-SCH and PCH transport channels in NB-IoT TS 36.212CR0285
- Correction on V2X sidelink communication in TS 36.300 TS 36.300CR1199
- 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
- Correction on MCS for V2X sidelink communication in TS 36.302 TS 36.302CR1196
- Correction on physical downlink control channel TS 38.213CR0020
+ 1 more changes
In Release 16, the PSSCH was fundamentally enhanced to support the new 5G V2X (Vehicle-to-Everything) sidelink communication, introducing NR (New Radio) Sidelink capabilities. This included the specification of physical layer procedures for shared spectrum channel access and corrections to ensure robust operation. The release also defined specific channel bandwidths and UE maximum output power requirements for V2X Communication operating bands.
- Introduction of 5G V2X with NR Sidelink TS 36.300CR1271
- Introduction of 5G V2X sidelink features into TS 38.212 TS 38.212CR0025
- Introduction of Physical Layer Enhancements for NR URLLC TS 38.212CR0026
- Introduction of shared spectrum channel access TS 38.213CR0071
- Correction for NR sidelink communication TS 36.300CR1287
- Clarification on LTE DAPS and sidelink on 36.300 TS 36.300CR1338
+ 27 more changes
In Release 17, key PSSCH enhancements introduced procedures for reporting sidelink HARQ-ACK on the uplink for configured grant Type 2 transmissions and defined UE procedures for receiving HARQ-ACK on the sidelink. The release also specified corrections for intra-UE multiplexing and semi-static channel occupancy, alongside clarifications for channel access type indications in both fallback and non-fallback DCI formats.
- Introduction of Rel-17 sidelink enhancements TS 37.985CR0001
- Introduction of NR sidelink enhancement TS 38.212CR0094
- Introduction of sidelink enhancements in NR TS 38.213CR0279
- Introduction of Rel-17 sidelink enhancements and concurrent Uu-PC5 bands TS 37.985CR0004
- Corrections on NR sidelink enhancement in 38.212 TS 38.212CR0100
- CR on ChannelAccess-Cpext in Fallback DCI TS 38.212CR0118
+ 9 more changes
In Release 18, the PSSCH function was enhanced as part of the NR sidelink evolution, introducing new capabilities including sidelink carrier aggregation (CA) and dynamic resource pool sharing for NR V2X. Furthermore, the release specified new sidelink channel access procedures to govern how devices access the channel for transmission. These additions were accompanied by necessary corrections and maintenance, such as fixes to the determination of PSFCH resources for a PSSCH.
- Introduction of sidelink CA and dynamic resource pool sharing for NR V2X TS 37.985CR0007
- Introduction of sidelink channel access procedures for Rel-18 NR sidelink evolution TS 38.201CR0003
- Introduction of Rel-18 NR sidelink evolution TS 38.212CR0149
- Introduction of NR sidelink evolution TS 38.213CR0509
- Corrections on Rel-18 NR sidelink evolution in 38.212 TS 38.212CR0164
- Corrections on Rel-18 NR sidelink evolution in 38.212 TS 38.212CR0187
+ 7 more changes
In Release 19, the PSSCH function saw the introduction of a new 3MHz channel bandwidth for V2X Communication, as detailed in the channel bandwidths per operating band for V2X. This addition was accompanied by corrections to the R19 NES adaptation procedures for common channels and signals to ensure proper operation.
Explore further
Broader topics and technologies where PSSCH plays a role.
Defining Specifications
3GPP specifications that define or reference PSSCH, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 36.101 vj30 | LTE UE Radio Transmission & Reception Requirements | 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 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.302 vj00 | E-UTRA Physical Layer Services | Rel-19 |
| TS 36.785 ve00 | LTE Sidelink V2V Services Study | Rel-14 |
| TS 36.786 ve00 | TR on V2X Services based on LTE sidelink | Rel-14 |
| TS 36.787 vf00 | V2X New Band Combinations for LTE | Rel-15 |
| TS 36.788 vf00 | V2X Phase 2 Technical Report for LTE | Rel-15 |
| TS 36.877 vc00 | LTE Device to Device Proximity Services | Rel-12 |
| TR 37.985 vj00 | Overview of V2X features in LTE and NR | Rel-19 |
| TS 38.101 vj31 | NR User Equipment Radio Transmissions | Rel-19 |
| TS 38.201 vj00 | NR Physical Layer General Description | 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 38.521 vj20 | NR Physical Layer UE Conformance Testing | Rel-19 |
| TR 38.785 vh00 | UE radio transmission for enhanced NR sidelink | Rel-17 |
| TR 38.786 vi20 | Technical Report for NR Sidelink Evolution | Rel-18 |
| TS 38.787 vj00 | UE Radio Transmission for Sidelink CA in ITS Band | Rel-19 |
| TS 38.793 vj00 | Simultaneous Rx/Tx Band Combinations TR | Rel-19 |
| TR 38.839 vh00 | Simultaneous Rx/Tx band combinations | Rel-17 |
| TS 38.863 vj10 | NR NTN RF and Co-existence Spec | Rel-19 |
| TR 38.868 vh00 | Optimizations of pi/2 BPSK uplink power in NR | Rel-17 |
| TR 38.881 vi00 | Technical Report on Lower MSD for Inter-band CA/EN-DC/DC | Rel-18 |
| TR 38.886 vg30 | NR V2X UE Radio Transmission & Reception | Rel-16 |
| TR 38.889 vg00 | NR-based access to unlicensed spectrum study | Rel-16 |
| TR 38.894 vi00 | Technical Report | Rel-18 |