Description
The Absolute Radio Frequency Channel Number (ARFCN) serves as a fundamental addressing mechanism for radio frequency resources in 3GPP cellular systems. It operates as a channel numbering scheme that maps to specific center frequencies within designated frequency bands. Each ARFCN corresponds to a particular carrier frequency, with the mapping defined by mathematical formulas that vary depending on the radio access technology (GSM, UMTS, LTE, or NR) and the frequency band in use. This systematic numbering allows network equipment and user devices to unambiguously identify and tune to specific radio channels without requiring direct frequency specification in hertz.
The ARFCN system works by establishing a linear relationship between channel numbers and actual radio frequencies. For GSM systems, the formula typically follows F = F_low + 0.2 × (N - N_off) where F is the carrier frequency in MHz, F_low is the band's lower edge frequency, N is the ARFCN, and N_off is the offset. In LTE and 5G-NR, more complex formulas account for different channel bandwidths and raster offsets. The network broadcasts ARFCN values in system information blocks, measurement configurations, and handover commands, enabling devices to identify which frequencies to monitor, measure, or camp on. Base stations use ARFCNs to configure their transmit frequencies and to coordinate frequency usage with neighboring cells.
Key components of the ARFCN system include the channel numbering formulas defined in 3GPP specifications for each frequency band, the channel raster (minimum frequency step between adjacent ARFCNs), and band-specific parameters like uplink/downlink offsets for FDD systems. The ARFCN plays multiple critical roles: it serves as a frequency reference for initial cell search and selection, enables precise radio resource management, facilitates inter-frequency and inter-RAT measurements, and supports mobility procedures like handovers. Network operators use ARFCN planning to allocate frequencies to cells while avoiding interference, and devices use ARFCN decoding to identify available networks during roaming.
In modern 5G networks, ARFCN has evolved into the NR-ARFCN system with a global frequency raster of 5 kHz, 15 kHz, or 60 kHz depending on the frequency range. This allows 5G to support wider bandwidths and more flexible spectrum arrangements while maintaining backward compatibility with earlier systems. The ARFCN concept remains essential for frequency synchronization, carrier aggregation configuration, and dual-connectivity setups where devices simultaneously connect to LTE and NR carriers identified by their respective ARFCNs.
Purpose & Motivation
ARFCN was created to solve the fundamental problem of frequency identification and management in cellular networks. Before standardized channel numbering, different manufacturers and operators used various methods to reference frequencies, leading to compatibility issues, especially for roaming devices and multi-vendor networks. The ARFCN system provides a universal language for frequency specification that works across different equipment vendors, network operators, and geographic regions.
The historical context for ARFCN development begins with GSM standardization in the 1980s, where the need for a simple, efficient method to identify RF channels became apparent as cellular networks expanded globally. Early cellular systems used direct frequency specifications, which were cumbersome for configuration and prone to errors. ARFCN addressed these limitations by creating an abstracted layer where network elements could reference frequencies using simple integers rather than precise hertz values. This abstraction simplified network planning, device implementation, and operational procedures.
ARFCN solves several practical problems: it enables efficient signaling (small integer values require fewer bits to transmit than frequency values), supports frequency band independence (the same ARFCN value can map to different actual frequencies in different bands), and facilitates measurement reporting standardization. As cellular technology evolved through UMTS, LTE, and 5G, the ARFCN concept proved adaptable to new requirements like carrier aggregation, where multiple ARFCNs identify component carriers, and network sharing scenarios, where different operators use the same physical infrastructure but different logical ARFCNs for their spectrum resources.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (36 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-5, normative work from Rel-15.
In Release 15, the ARFCN function was updated to include a mirror of the operating band and frequency range declaration from New Radio (NR). This was introduced alongside corrections to text and tables for OTA measurements, specifically for the Adjacent Channel Leakage Ratio and Operating Band Unwanted Emissions.
In Release 16, the ARFCN-related updates primarily focused on corrections and clarifications to channel spacing definitions, particularly for Carrier Aggregation (CA) scenarios involving NR and between E-UTRA and NR carriers. These changes included specific corrections to the nominal channel spacing for CA and the introduction of rules for channel spacing between different radio access technologies. The updates also involved corrections to NR-ARFCN values for positioning reference points and related intra/inter-frequency measurement procedures for NR positioning.
- Add new general abbreviations MCC Note: CR cover sheet wrongly shows CR number as "1118". TS 21.905CR0118
- LPP Layer interaction with lower layers for Positioning Frequency layer and Measurement Gap TS 37.355CR0288
- Correction to NR-ARFCN of the TRP TS 37.355CR0306
- Corrections to intra/inter-frequency measurement for NR positioning TS 38.215CR0029
- CR to TS 37.104: CA channel spacing TS 37.104CR0869
- Introduction of channel spacing between E-UTRA and NR carriers TS 37.104CR0888
+ 9 more changes
In Release 17, the ARFCN function was extended to support new channel bandwidths of 35 MHz and 45 MHz, as detailed in updates to multiple technical specifications including TS 37.104, TS 37.141, and TS 37.145-2. This introduction required corresponding modifications to RF requirements, such as the Adjacent Channel Leakage power Ratio (ACLR), and to transmitter and receiver RF requirements which use the channel bandwidth as a reference. Additionally, the release included updates to spurious emissions limits for Active Antenna System (AAS) Base Stations to ensure coexistence with systems in other frequency bands.
- 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
- (NR_RAIL_EU_1900MHz_TDD-Core) CR to TR 38.852: complementary update for the n101 cab-radio aspects, Rel-17 TS 38.852CR0009
- (NR_RAIL_EU_900MHz-Core) CR to TR 38.853: complementary update for the n100 cab-radio aspects, Rel-17 TS 38.853CR0009
- 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 ARFCN function was updated to formally support a new NR channel bandwidth of 3 MHz in FR1. This required defining the associated frequency offset parameter, FoffsetRAT, for this specific bandwidth to ensure proper transmitter and receiver RF requirements. The changes were implemented across core and performance specification documents to integrate this new channel bandwidth into the existing framework.
- 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
In Release 19, the primary update to the ARFCN function was the introduction of a new 7 MHz channel bandwidth for NR FR1, requiring updates to multiple technical specifications to define its associated RF requirements and performance criteria. This addition expanded the set of standardized channel bandwidths available for network deployment and operation. The release also included corrections related to UE capability signaling for positioning SRS frequency hopping, specifically for non-RedCap UEs.
- 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
- Introduction of UE capability for SRS frequency hopping for non-RedCap UE in 37355 [Pos_SRSHop] TS 37.355CR0553
- (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 ARFCN plays a role.
Defining Specifications
3GPP specifications that define or reference ARFCN, 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 34.114 vc20 | Radiated Performance Test Procedure for UE/MS | Rel-12 |
| TS 36.355 vj00 | LTE Positioning Protocol (LPP) | 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 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.544 vg70 | UE Radiated Performance Test Procedures | Rel-16 |
| 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 |
| TR 37.900 vj00 | Multi-Standard Radio (MSR) Base Station Requirements | Rel-19 |
| TS 38.215 vj10 | NR Physical Layer Measurements | Rel-19 |
| TR 38.852 vh50 | 1900MHz NR band for European Rail Mobile Radio | Rel-17 |
| TR 38.853 vh50 | 900MHz NR Band for European Rail Mobile Radio | Rel-17 |
| TS 38.870 vj20 | Enhanced OTA Test Methods for NR FR1 TRP/TRS | Rel-19 |
| TR 43.901 vj00 | Generic Access to A/Gb Interface Feasibility Study | Rel-19 |
| TR 45.914 vj00 | MUROS Feasibility Study for Voice Capacity | Rel-19 |