Description
The UTRA Absolute Radio Frequency Channel Number (UARFCN) is a fundamental parameter in UMTS (3G) networks that defines the center frequency of a radio carrier. It is an integer value that maps to a specific frequency in MHz according to formulas defined in 3GPP specifications. The use of a channel number, rather than a direct frequency value, simplifies network configuration, UE implementation, and measurement reporting. For Frequency Division Duplex (FDD) mode, separate UARFCN values are assigned for the uplink (UL) and downlink (DL) carriers, which are paired with a fixed duplex spacing. For Time Division Duplex (TDD) mode, a single UARFCN defines the carrier frequency used for both transmission directions.
The calculation of the actual frequency from the UARFCN (N) follows the formula: F (MHz) = F_Offset + (N * Channel_Spacing). The values for F_Offset and Channel_Spacing differ between operating bands and duplex modes. For example, in the core UMTS Band I (2100 MHz FDD), the downlink UARFCN calculation uses F_Offset = 0 MHz and a step size of 0.2 MHz, so UARFCN N=10562 corresponds to 2112.4 MHz. This systematic mapping allows every possible carrier within a band's defined range to be addressed uniquely. UARFCN is used extensively in system information blocks (SIBs) broadcast by Node Bs to inform UEs of the serving and neighboring cell frequencies, in measurement control messages from the RNC, and in measurement reports sent by UEs.
Its role extends beyond mere identification. UARFCN is key for cell selection and reselection, handover procedures, and network planning. By reporting measured signal quality (e.g., CPICH RSCP, Ec/No) against a specific UARFCN, the UE provides the network with a clear picture of the radio environment. The RNC uses this information to make mobility decisions. The concept of ARFCN was later extended to E-UTRA with EARFCN for LTE and NR-ARFCN for 5G NR, maintaining the same principle of channel numbering but with different formulas and ranges to accommodate new spectrum and wider channel bandwidths.
Purpose & Motivation
UARFCN was created to provide a standardized, unambiguous method for identifying carrier frequencies within the UTRA system, replacing the need to use raw frequency values in signaling and configuration. In early cellular systems, while channel numbers existed, the rapid expansion of spectrum bands and the introduction of wideband CDMA with UMTS necessitated a more flexible and scalable numbering scheme. Using direct frequency values in messages would be inefficient, prone to error, and would not elegantly handle the variety of global frequency bands with different duplex spacings and offsets.
The primary problem UARFCN solves is ensuring interoperability and consistent frequency reference across all network equipment and user terminals, regardless of the manufacturer or the specific frequency band being used. It abstracts the physical frequency, allowing higher-layer protocols and procedures to work with simple integer values. This simplifies UE implementation for global roaming, as the device only needs to know the UARFCN-to-frequency mapping formulas for its supported bands. For network operators, it streamlines frequency planning, neighbor cell list configuration, and drive test analysis. The creation of UARFCN, alongside the detailed band specifications, was a critical enabler for the global deployment of UMTS, providing a clear and efficient lingua franca for the radio layer that has been carried forward into all subsequent 3GPP radio access technologies.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (45 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the UARFCN function was updated through a mirroring of operating band and frequency range declarations from New Radio (NR) to ensure alignment. This change was part of broader updates to the specification, which also included the implementation of 1024QAM and sTTI for E-UTRA, alongside the removal of UTRA TDD. These modifications were consolidated within the context of Over-The-Air (OTA) testing requirements for adjacent channel leakage and unwanted emissions.
- CR to TS 37.145-2: OTA Adjacent Channel Leakage Ratio (6.7.3) and OTA Operating band unwanted emissions (6.7.5) - corrections to text and tables TS 37.145CR0055
- CR to TS 37.145-2: UTRA TDD removal TS 37.145CR0063
- CR to TS 37.145-2: Implementation of 1024QAM for E-UTRA, Rel-15 TS 37.145CR0084
- CR to TS 37.145-2: Implementation of sTTI for E-UTRA, Rel-15 TS 37.145CR0085
- CR to TS 37.145-2: mirror of operating band and frequency range declaration from NR, Rel-15 TS 37.145CR0133
In Release 16, the UARFCN function itself was not directly modified. The primary updates relevant to UTRA frequencies in this release concerned the introduction of new multi-Radio Access Technology (RAT) coexistence requirements, specifically for NR + UTRA/GSM combinations. These changes focused on defining channel spacing and adjacent channel leakage power ratio (ACLR) requirements to ensure proper operation when these technologies are deployed together.
- Add new general abbreviations MCC Note: CR cover sheet wrongly shows CR number as "1118". TS 21.905CR0118
- Introduction of requirements for NR + UTRA/GSM combinations TS 37.104CR0863
- Introduction of requirements for NR + UTRA/GSM combinations TS 37.141CR0871
- Removal of CA bands list for E-UTRA TS 37.104CR0824
- Removal of CA bands list for E-UTRA TS 37.141CR0822
- CR to TS 37.145-2: Corrections to single RAT E-UTRA additional requirements for band 89, Rel-16 TS 37.145CR0255
+ 14 more changes
In Release 17, the primary update to the UARFCN function was the introduction of new channel bandwidths of 35 MHz and 45 MHz for UTRA, as detailed in changes to the Base Station conformance specifications. This required corresponding updates to RF requirements, including Adjacent Channel Leakage power Ratio (ACLR) and spurious emissions limits, to support these wider channel bandwidths. Additionally, a new Base Station capability set for multi-RAT operation (NR+EUTRA+UTRA) was introduced in the conformance testing framework.
- CR to 37.104: Introduction of requirements for 35 and 45MHz channel bandwidths TS 37.104CR0949
- CR for TS 37.141: introduction of channel bandwidths 35MHz and 45MHz TS 37.141CR0990
- CR for TS 37.145-2: introduction of channel bandwidths 35MHz and 45MHz TS 37.145CR0314
- CR to TS 34.124: corrections of the UTRA UE EMC specification, Rel-17 TS 34.124CR0047
- CR to TS 37.145-2: Introduction of new BS capability set for NR+EUTRA+UTRA, Rel-17 TS 37.145CR0287
- CR to 37.145-2 to modify AAS BS OTA Spurious emissions limits for co-existence with systems operating in other frequency bands in R17 TS 37.145CR0302
In Release 18, the UARFCN function was updated to account for new NR carrier configurations, specifically the introduction of a 3 MHz channel bandwidth for NR in FR1. This required defining new frequency offset values (FoffsetRAT) for these narrower NR channels relative to UTRA carriers for co-existence testing. The changes were implemented through updates to the core and performance parts of the conformance test specifications TS 37.104 and TS 37.141.
- CR to TS 37.141 - Consideration of NR 3 MHz channel bandwidth TS 37.141CR1068
- (NR_FR1_lessthan_5MHz_BW-Core) CR to TS 37104 - FoffsetRAT for NR 3MHz channel BW TS 37.104CR1023
- (NR_FR1_lessthan_5MHz_BW-Perf) CR to TS 37141 - FoffsetRAT for NR 3MHz channel BW TS 37.141CR1094
- [AASenh_BS_LTE_UTRA-Perf] CR to TR 37.145-2: Corrections on tables for E-UTRA in-channel selectivity test requirement TS 37.145CR0357
- (NR_newRAT-Perf) CR to TS37.145-2: Addition of some missing band numbers TS 37.145CR0376
- (AAS_BS_LTE_UTRA-Core) CR to TS 37.145-2 on correction for single RAT E-UTRA operation TS 37.145CR0382
In Release 19, the primary change related to UARFCN was the removal of UTRA TDD from the Multi-Standard Radio (MSR) Base Station specifications, as detailed across several Change Requests to technical specifications 37.104, 37.141, and 37.145-2. This change signifies that UTRA TDD is no longer a mandatory supported mode for MSR Base Stations, affecting the applicable channel bandwidths and radio frequency requirements. The release also introduced the new 7 MHz channel bandwidth for NR FR1, but this is a separate NR-related update and not a change to the core UTRA/UARFCN function itself.
- CR to TS37.104 Introduction of 7 MHz NR FR1 channel bandwidth TS 37.104CR1028
- CR to TS 37113 - Introduction of 7 MHz channel BW TS 37.113CR0142
- CR to TS37.141 Introduction of 7 MHz NR FR1 channel bandwidth TS 37.141CR1098
- CR to TS 37.145-2: 7MHz channel bandwidth introduction TS 37.145CR0398
- (RInImp9-Rfmulti,TEI17) CR to 37.104: Removal of UTRA TDD from MSR BS specifications TS 37.104CR1036
- (NR_FR1_7MHz_BW-Perf) CR to TS 37.113: Correction of channel bandwidths for performance criteria for continuous phenomena TS 37.113CR0143
+ 2 more changes
Explore further
Broader topics and technologies where UARFCN plays a role.
Defining Specifications
3GPP specifications that define or reference UARFCN, 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 25.104 vj00 | UTRA FDD Base Station RF Characteristics | Rel-19 |
| TS 25.106 vj00 | UTRA FDD Repeater RF Performance Requirements | Rel-19 |
| TS 25.111 vj00 | LMU RF Characteristics for UTRA FDD | Rel-19 |
| TS 25.143 vj00 | UTRA FDD Repeater RF Test Requirements | Rel-19 |
| TS 25.423 vj00 | UTRAN RNSAP Specification | Rel-19 |
| TS 25.433 vj00 | Node B Application Part (NBAP) Protocol | Rel-19 |
| TR 25.931 vj00 | UTRAN Signalling Procedures Examples | Rel-19 |
| TS 34.124 vj00 | EMC Requirements for 3G UTRA Terminals | Rel-19 |
| TS 36.124 vj00 | EMC for E-UTRA User Equipment | Rel-19 |
| TS 37.104 vj10 | MSR Base Station RF Characteristics | Rel-19 |
| TS 37.113 vj00 | EMC Requirements for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.141 vj10 | RF Test Methods for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.145 vj10 | AAS Base Station Conducted Conformance Testing | Rel-19 |
| TS 37.802 va10 | MSR BS RF Requirements for Non-Contiguous Spectrum | Rel-10 |
| TS 37.812 vb30 | Multi-band Multi-standard Radio BS Requirements | Rel-11 |
| TS 37.814 vc00 | L-band Supplemental Downlink for UTRA/E-UTRA | Rel-12 |
| TR 37.900 vj00 | Multi-Standard Radio (MSR) Base Station Requirements | Rel-19 |