NREF

NR Absolute Radio Frequency Channel Number

Radio Access Network →
Introduced in Rel-17 Also in: User Equipment

NREF is the unique numeric identifier for each radio frequency channel in 5G NR, providing a standardized global reference for carrier frequencies.

Category
Radio Access Network
Introduced
Rel-17
Where
Radio Access Network › NG-RAN (5G)
Also touches
1 segments
Specifications
9 specs
NREF Description Purpose Related Classification Detected Changes Specifications

Description

The NR Absolute Radio Frequency Channel Number (NR-ARFCN) is a fundamental parameter defined in 3GPP specifications that maps to a specific RF carrier frequency in the 5G New Radio (NR) system. It is a linear, dimensionless integer that uniquely identifies a frequency channel across all NR frequency bands, including both Frequency Range 1 (FR1: sub-7 GHz) and Frequency Range 2 (FR2: mmWave, 24.25 GHz and above). The mapping between an NREF value and its corresponding absolute frequency in Hertz is defined by a specific formula that differs between FR1 and FR2, accounting for the different channel raster sizes (e.g., 5 kHz, 15 kHz, 60 kHz, 100 kHz). This formula ensures that each valid NREF points to a channel raster position where the carrier center frequency can be placed, aligning with synchronization signal block (SSB) and channel bandwidth configurations.

Architecturally, the NREF is used throughout the NR protocol stack and network interfaces. In the air interface (Uu), it is signaled in system information blocks (SIBs) like SIB1 to indicate the downlink and uplink carrier frequencies for a cell. It is a critical component in measurement reporting, where the UE reports detected cells using their Physical Cell Identity (PCI) and their corresponding NREF. For network management and testing, NREF is used in specifications defining RF requirements (e.g., 38.101 for UE radio transmission and reception, 38.104 for Base Station radio transmission and reception) and conformance testing (e.g., 38.141 for base station conformance testing, 38.521 for UE conformance testing). It provides a common reference point for defining transmitter and receiver characteristics, such as output power, unwanted emissions, and reference sensitivity, at specific frequencies.

Its role extends to network deployment and optimization. Operators use NREF values in network planning tools to define carrier frequencies. In dual-connectivity (EN-DC, NR-DC) or carrier aggregation (CA) scenarios, secondary cells (SCells) are identified by their NREF alongside their PCI. The NREF is also integral to the NR frequency band definitions; each operating band is associated with a specific range of NREF values for uplink and downlink. This systematic numbering replaces the need to communicate absolute frequencies in Hertz in many signaling messages, simplifying protocol design and ensuring global consistency. The concept evolves from the EARFCN used in LTE, adapted for NR's wider frequency range and more flexible numerology.

Purpose & Motivation

The NREF was created to provide a standardized, efficient, and unambiguous method for identifying radio carrier frequencies in the 5G NR system. Prior to 5G, LTE used the EARFCN (E-UTRA Absolute Radio Frequency Channel Number). With NR's introduction, which supports a vastly expanded spectrum from below 1 GHz to millimeter waves (up to 100 GHz), a new numbering scheme was necessary. The existing LTE scheme was not designed to cover these extreme frequencies or the new channel raster granularities required for NR's diverse use cases, such as wideband mmWave carriers. The NREF solves the problem of frequency referencing across this heterogeneous landscape.

A key motivation was to ensure backward compatibility and forward flexibility in protocol design. By defining a linear formula-based mapping, the system can easily incorporate new frequency bands in future releases without redesigning the signaling framework. It addresses the limitation of using absolute frequency values directly in signaling, which would be inefficient in terms of message size and prone to rounding errors. The NREF provides a compact integer representation that can be easily processed by network elements and user equipment.

Furthermore, it solves critical interoperability and testing challenges. For global roaming and equipment certification, a universal frequency identifier is essential. Manufacturers, operators, and test equipment vendors all rely on the NREF as a common language for specifying RF characteristics, conducting conformance tests, and ensuring that UEs can correctly tune to and operate on any NR carrier worldwide. It is foundational for automated network configuration, self-organizing network (SON) functions, and spectrum sharing scenarios.

Classification

Part ofARFCN
Related approachesEARFCN

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (70 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Rel-15 2 changes

In Release 15, the NREF (NR Absolute Radio Frequency Channel Number) function was introduced as the foundational system for defining and calculating the center frequencies of all NR carriers. This new numbering scheme, specified in TS 38.104, provided a unified method to identify channel locations across the two defined frequency ranges, FR1 and FR2, enabling global interoperability for 5G NR equipment.

  • CR to TS 38.104 on Combined updates from RAN4 #90 This document combines the proposed changes in the following Draft CRs from RAN4 #90: - R4-1900284, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1900763, "Draft CR to TS 38.104: Update of performance requirement numbers for DFT-s-OFDM based PUSCH" - R4-1900876, "Draft CR to TS 38.104: On RX spurious emissions requirement" - R4-1900968, "Draft CR for 38.104: Performance requirements for NR PUCCH format 1" - R4-1901329, "Draft CR to 38.104: Annex C.6 correction" - R4-1901330, "Draft CR to 38.104: Abbreviations addition" - R4-1901387, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1901474, "Draft CR to TS 38.104: Corrections on transmitter co-existence and co-location requirements" - R4-1901483, "Draft CR to TS 38.104: Corrections on general intermodulation requirement" - R4-1902239, "Draft CR to TS 38.104: Addition of missing EIRP/EIS definitions in terminology in clause 3.1" - R4-1902241, "Draft CR to 38.104; clarification of BS power limits" - R4-1902245, "Draft CR to 38.104: Correction to FR2 OTA Interfering signal mean power units" - R4-1902246, "Draft CR to 38.104; Correction to definition of OTA reference sensitivity" - R4-1902260, "draft CR to TS 38.104 - update emissions scaling" - R4-1902338, "Draft CR: Update on FR1 range extension for TS38.104" - R4-1902389, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1902394, "Draft CR to TS 38.104 – PUSCH requirements with CP-OFDM for FR2" - R4-1902396, "CR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1902444, "Draft CR to TS 38.104: Editorial CR for BS demodulation requirements" - R4-1902561, "Draft CR for updating PRACH performance requirements in TS38.104" - R4-1902571, "Corrections to 38.104 Delay profile calculation" - R4-1902642, "Draft CR to TS 38.104: Correction on multi-band operation related requirements" TS 38.104CR0019
  • CR to TS 38.104 Combined updates from RAN4 #90bis and RAN4#91 From RAN4 #90bis: - R4-1903105, "Draft CR to TS 38.104: Corrections on terminologies and editorial errors" - R4-1903319, "Draft CR to TS 38.104: removal of unused definition: "minimum EIRP level under extreme condition"" - R4-1903320, "Draft CR to TS 38.104: OSDD information correction" - R4-1903457, "Draft CR to TS 38.104: Removal of FFS for FR2 TDD OFF power level requirement in clause 9.5" - R4-1903499, "Draft CR to 38.104: Correction to unwanted emissions mask for bands n7 and n38" - R4-1903836, "Draft CR to TS 38.104: Correction on description on multi-band operation in section 4.8" - R4-1904024, "Draft CR to TS 38.104 Applicability rules for BS demodulation" - R4-1904234, "draftCR: Correlation matrix for 8Rx in TS 38.104" - R4-1904723, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1904726, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1904729, "Draft CR on PRACH performance requirements in TS38.104" - R4-1904734, "Draft CR on TS 38.104 Performance requirement for PUCCH format 1" - R4-1904735, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1904739, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1904745, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1904799, "Draft CR to TS 38.104: FRC update for PUSCH FR1 mapping type B and FR2 DMRS 1+1" - R4-1904816, "Draft CR : Clarification on step 5 and step 6 for delay profiles calculation (38.104)" - R4-1904842, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1905126, "draft CR to 38.104 for TAE requirements" - R4-1905139, "draft CR to TS 38.104 on EVM measurement (Annex B and C)" - R4-1905140, "Draft CR: editorial correction on FR1 spurious emission requirement in TS38.104" - R4-1905143, "Draft CR for TS 38.104: Addition of NOTE for transmitter intermodulation requirements in certain regions" - R4-1905144, "Draft CR to TS 38.104: FRC reference corrections for the Rx requirements" - R4-1905145, "Draft CR to TS 38.104: Clarification on application of interfering signal offsets for ACS, blocking and intermodulation requirements" - R4-1905148, "Draft CR to TS 38.104: Corrections on out-of-band blocking requirement" From RAN4 #91: - R4-1906002, "Draft CR to 38.104: Subclause 6.7 and 9.8 transmitter intermodulation – correction of interfering signal type" - R4-1906096, "Draft CR to 38.104: Correction of frequency range for OTA spurious emissions" - R4-1906311, "Draft CR to 38.104: Correction on FRC (Annex A)" - R4-1906346, "Removal of n65 in Rel-15 38.104" - R4-1906915, "Draft CR to TS 38.104: Clarification on application of interfering signal offsets for OTA ACS, blocking and intermodulation requirements" - R4-1906918, "Draft CR to TS 38.104: Clarification on type of interfering signal for ACS, in-band blocking and ICS requirements" - R4-1907110, "Draft CR to TS 38.104: correction of the fundamental frequency limit of 2.55GHz for the spurious emissions" - R4-1907246, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1907249, "Draft CR to TS 38.104: Correction on the terminology in PUSCH FRC tables" - R4-1907252, "Draft CR to TS38.104: Updates of PRACH performance requirements" - R4-1907255, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1907258, "Draft CR on NR UCI on PUSCH performance requirements for TS 38.104" - R4-1907261, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1907266, "Draft CR on TS 38.104 Performance requirement for PUCCH format 1" - R4-1907267, "Draft CR on TS 38.104 Performance requirement for multi-slot PUCCH format 1" - R4-1907272, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1907275, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1907277, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1907629, "Draft CR to 38.104: Term “reference signal” replacing by term “ideal signal” in EVM context" - R4-1907634, "Draft CR to 38.104: corrections to the EVM annex" - R4-1907659, "Draft CR to TS 38.104 on Spurious emission Category B in FR2" - R4-1907661, "Draft CR to 38.104 Definition of contiguous transmission bandwidth" - R4-1907662, "Draft CR to 38.104: BS TAE requirements" - R4-1907664, "Draft CR to 38.104: Clarification of interferer RB frequency for narrowband blocking" - R4-1907672, "Draft CR for TS 38.104: Correction on EVM" - R4-1907689, "Correction to CA carrier spacing" TS 38.104CR0029
Rel-16 22 changes

In Release 16, the NREF function was expanded through the introduction of wider channel bandwidths for several NR operating bands, including n1, n7, n38, n66, n77, and n78, and the addition of new bandwidths such as 30 MHz for n50 and 40 MHz for n38. These enhancements were complemented by performance requirement updates for various channels, including PUSCH, PUCCH, and PRACH, under conditions like high-speed train (HST) scenarios. Furthermore, Release 16 introduced specifications for LTE/NR spectrum sharing in band n48 and included corrections and clarifications on channel raster and operational parameters.

  • Addition channel bandwidth of 30MHz for n50 in TS 38.104 TS 38.104CR0031
  • CR for TS 38.104: adding wider channel bandwidths in Band n7 TS 38.104CR0037
  • CR for TS 38.104: adding wider channel bandwidths in Band n77/n78 TS 38.104CR0105
  • CR for TS 38.104: Addition channel bandwidth of 40MHz for n38 TS 38.104CR0106
  • Introducing new channel bandwidth for band n28 TS 38.104CR0131
  • CR for TS 38.104: adding wider channel bandwidths for n66 TS 38.104CR0139

+ 16 more changes

Rel-17 16 changes

In Release 17, the NREF (NR-ARFCN) function was updated to support new channel bandwidths, including 35MHz and 45MHz, and to add a 5 MHz channel bandwidth for band n41. Furthermore, specific corrections and enhancements were made, such as correcting the channel raster for band n259 and defining a channel raster exception for 40 MHz channels in band n28.

  • Big CR to 38.104 - Additional Channel BW TS 38.104CR0258
  • Big CR to 38.104 - Additional Channel BW TS 38.104CR0291
  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0319
  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0343
  • CR for TS 38.104: introduction of channel bandwidths 35MHz and 45MHz NOTE The CR is not implemented TS 38.104CR0341
  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0356

+ 10 more changes

Rel-18 22 changes

In Release 18, key enhancements for the NREF (NR-ARFCN) function included the introduction of a 3 MHz channel bandwidth for new deployments and the specification of an enhanced channel raster to provide greater flexibility. These changes, detailed in updates to TS 38.104, also involved adding new channel raster points for specific frequency ranges like 5925-5945 MHz and providing clarifications for synchronization signal (SS) raster entries associated with the new bandwidths.

  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0450
  • Big CR to TS 38.104 on introduction of 3 MHz channel bandwidth TS 38.104CR0500
  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0512
  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0538
  • CR to TS38.104: Introduction of an enhanced channel raster TS 38.104CR0536
  • CR to TS 38.104 on clarification of applicable SS raster entries for 3 MHz channel bandwidth TS 38.104CR0528

+ 16 more changes

Rel-19 8 changes

In Release 19, the NREF function was extended to support new channel bandwidths, specifically the introduction of a 7 MHz channel bandwidth and the addition of a 3 MHz channel. These additions required updates to the minimum requirements for reference sensitivity levels, particularly for base stations supporting NB-IoT operation in NR in-band for the 3 MHz channel bandwidth. The changes also involved defining new channel arrangements and updating performance requirements for these newly supported bandwidths across several technical specifications.

  • Big CR to TS 38.104: Adding channel BW support in existing NR bands TS 38.104CR0685
  • CR to 38.104 on adding new UL channel bandwidth to band n48 TS 38.104CR0698
  • Running CR to TS 38.104 - Introduction of 7 MHz channel BW TS 38.104CR0725
  • CR to TS 38.141-2: 7MHz channel bandwidth introduction TS 38.141CR0666
  • Addition of the 3MHz channel to TR 38.741 TS 38.741CR0010
  • Addition of the 3MHz channel to TR 38.863 TS 38.863CR0036

+ 2 more changes

Explore further

Broader topics and technologies where NREF plays a role.

Topics
OAM (Operations & Maintenance)SON (Self-Organizing Networks)RRC (Radio Resource Control)Spectrum & CoexistenceRoaming & InterconnectTesting & Conformance
Technologies
LTE5G

Defining Specifications

3GPP specifications that define or reference NREF, with the latest known release. Sourced from the 3GPP document catalog — see methodology.

SpecificationTitleRelease
TS 38.101 vj31 NR User Equipment Radio Transmissions Rel-19
TS 38.104 vj20 NR Base Station RF Requirements Rel-19
TS 38.141 vj20 NR Base Station RF Conformance Testing Part 1 Rel-19
TS 38.521 vj20 NR Physical Layer UE Conformance Testing Rel-19
TS 38.741 vj00 NTN L-/S-band for NR Technical Specification 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
TR 38.847 vh20 NR 47.2-48.2 GHz Frequency Range Rel-17
TS 38.863 vj10 NR NTN RF and Co-existence Spec Rel-19