Description
The Physical Reader-to-Device Channel (PRDCH) is a downlink physical channel defined in the 5G New Radio (NR) sidelink (SL) interface, standardized from 3GPP Release 19 onwards. It is a key component of the NR sidelink communication framework, which supports direct device-to-device (D2D) connectivity. The PRDCH is specifically used by a device acting as a 'reader' or initiating side to transmit data and control information to a target 'device' within a sidelink communication session. This channel operates on the PC5 interface, the reference point for direct communication between user equipments (UEs), and is designed to work in both in-coverage and out-of-coverage scenarios, with or without network scheduling assistance.
In terms of physical layer structure, the PRDCH is mapped to specific physical resources within the NR sidelink resource grid. It utilizes the NR flexible numerology, supporting various subcarrier spacings and cyclic prefix lengths to adapt to different frequency bands (including FR1 and FR2) and service requirements (e.g., high reliability, low latency). The channel carries a transport block which includes user data for sidelink communication. Its transmission involves typical NR physical layer procedures: channel coding (likely using LDPC codes for data), modulation (QPSK, 16QAM, 64QAM, 256QAM), layer mapping, and precoding. The resources for PRDCH can be autonomously selected by the transmitting UE (Mode 2) or scheduled via sidelink control information (SCI) received from the network or another UE.
The role of PRDCH is central to enabling efficient sidelink services such as public safety communications, vehicle-to-everything (V2X) messaging, and commercial proximity services. It works in conjunction with other sidelink channels: the Physical Sidelink Control Channel (PSCCH) carries the associated SCI that schedules and describes the PRDCH transmission (e.g., resource allocation, modulation and coding scheme), and the Physical Sidelink Feedback Channel (PSFCH) may carry hybrid automatic repeat request (HARQ) feedback. The PRDCH supports advanced features integral to NR, including beamforming and MIMO for enhanced coverage and capacity in higher frequencies, and is designed to meet stringent requirements for ultra-reliable low-latency communication (URLLC) and enhanced mobile broadband (eMBB) over sidelink. Its design ensures spectral efficiency and reliable direct communication, forming a foundational data pipe for NR D2D.
Purpose & Motivation
The PRDCH was created to fulfill the need for a high-performance, native NR physical data channel for sidelink communication, as previous D2D standards in LTE (based on the PSSCH) were not optimized for the full capabilities of 5G. The motivation stems from expanding use cases for direct device communication beyond traditional public safety, including advanced V2X applications (like cooperative sensing and autonomous driving), industrial IoT, and immersive extended reality (XR) experiences that require high data rates, very low latency, and high reliability between devices.
It addresses limitations of the LTE sidelink, which was primarily designed for lower data rates and less dynamic resource allocation. The NR sidelink, with channels like PRDCH, leverages the full 5G NR physical layer advancements such as flexible numerology, advanced channel coding, and beam-based operation to support a wider range of spectrum (including mmWave), improve spectral efficiency, and reduce latency. The creation of a dedicated 'reader-to-device' channel nomenclature also helps clarify the directional nature of communication in more complex sidelink scenarios involving discovery, groupcast, and unicast, providing a standardized and efficient mechanism for data transfer in the evolving landscape of proximity-based services.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (14 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the PRDCH (Physical Reader-to-Device channel) function was introduced with foundational physical layer definitions including specific R2D channel bandwidths, transmission bandwidth configurations, and guardband requirements for operation in bands n5, n8, and n28. This release also established the AIoT-ARFCN for channel raster and defined the mapping between the channel raster and physical resource elements. The specifications provide the complete RF characteristics framework for the Ambient IoT device's operation on the PRDCH.
In Release 16, the new PRDCH (Physical reader-to-device channel) function introduced specific channel arrangements and bandwidths for the R2D (reader-to-device) link, including defined transmission bandwidth configurations and guardbands for operation in bands n5, n8, and n28. This release also specified the mapping between the channel raster and the corresponding resource element for the allocated physical resource blocks. Additionally, it defined the AIoT-ARFCN for channel numbering and established the relationship between the R2D channel bandwidth, guardband, and transmission bandwidth configuration.
- Mapping of Uplink Traffic to Backhaul RLC Channels TS 38.300CR0255
In Release 17, the new specifications for the PRDCH (Physical reader-to-device channel) function introduced defined R2D (reader-to-device) channel bandwidths, transmission bandwidth configurations, and associated guardbands for specific operating bands. This included detailed technical parameters such as supported subcarrier spacings and the mapping between the channel raster and resource elements for Ambient IoT devices. The groundwork was also laid for device-to-reader (D2R) link characteristics, specifying device channel bandwidths and transmission parameters separate from the reader's configuration.
- Running CR to 38300 for Multi-USIM devices support TS 38.300CR0422
In Release 18, the enhancements for the PRDCH function introduced specific R2D (Reader-to-Device) channel bandwidths and transmission bandwidth configurations for new operating bands, including n5, n8, and n28. The release defined detailed requirements for minimum guardbands and RB alignment to ensure coexistence within these bands. Furthermore, it established a precise channel raster to resource element mapping for RF reference frequencies, governed by the new AIoT-ARFCN numbering scheme.
In Release 19, the PRDCH (Physical reader-to-device channel) function saw corrections and clarifications to the Ambient IoT physical layer and device RF requirements. The updates included specific corrections to the A-IoT device symbol, output RF spectrum emissions, and testing procedures as defined in TS 38.191. These changes refined technical parameters such as the R2D transmission bandwidth configuration, guard bands, and the mapping between the channel raster and resource elements for the supported operating bands.
- CR for TS 38.191, Correction on A-IoT Device Symbol TS 38.191CR0001
- CR for TS 38.191, Correction on A-IoT Device Output RF spectrum emissions TS 38.191CR0002
- Corrections for device RF requirements TS 38.191CR0006
- CR on 38.191 for A-IoT device testing TS 38.191CR0003
- Corrections to the Ambient IoT physical layer TS 38.291CR0001
- Corrections to the Ambient IoT physical layer TS 38.291CR0002
In Release 20, the PRDCH (Physical reader-to-device channel) function was enhanced for Ambient IoT in outdoor NR to support active devices. This included the introduction of specific R2D (Reader-to-Device) channel bandwidths and transmission bandwidth configurations for defined operating bands like n5, n8, and n28. The release also formalized the channel arrangement using AIoT-ARFCN for channel raster and defined the mapping between the channel raster and resource elements for these active device scenarios.
Explore further
Broader topics and technologies where PRDCH plays a role.
Defining Specifications
3GPP specifications that define or reference PRDCH, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 38.191 vj00 | NR Ambient IoT RF Characteristics | Rel-19 |
| TS 38.291 vj20 | Ambient IoT Physical Layer Specification | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.391 vj00 | NR; Ambient IoT MAC Protocol Spec | Rel-19 |
| TS 38.769 vk00 | Ambient IoT Solutions in NR | Rel-20 |