Frequency Range

Description

In 3GPP specifications, a Frequency Range (FR) is a formal designation that groups radio frequency spectrum into distinct operational ranges for New Radio (NR) and, by extension, provides context for LTE. The primary FRs for NR are FR1 (410 MHz – 7125 MHz) and FR2 (24250 MHz – 52600 MHz). Each FR is defined with a specific set of technical parameters, radio frequency (RF) requirements, and supported features that govern the design and operation of User Equipment (UE) and gNBs (base stations). This categorization is not merely about frequency but encompasses the entire physical layer and RF system design appropriate for those bands.

The architecture of FR definitions is embedded within the 3GPP technical specifications for NR (38-series). For each FR, the specifications define the supported channel bandwidths, subcarrier spacings (SCS), transmission bandwidth configurations, and the associated NR-ARFCN (Absolute Radio Frequency Channel Number) table for unambiguous frequency referencing. FR1, often called 'sub-6 GHz,' includes both traditional cellular bands and new mid-band spectrum. It supports a wide variety of channel bandwidths up to 100 MHz, multiple subcarrier spacings (15, 30, 60 kHz), and is the primary range for wide-area coverage. FR2, known as the 'mmWave' range, includes much wider channel bandwidths (up to 400 MHz), primarily uses 60 kHz and 120 kHz SCS, and introduces specific challenges and solutions for high path loss, such as beamforming and beam management as core operational requirements.

How FR works is foundational to network and device operation. When a network is deployed in a specific band, it is categorized under an FR. This categorization dictates the RF performance requirements the UE must meet, such as maximum output power, unwanted emission limits, and receiver sensitivity. It determines the permissible physical layer configurations: for example, a carrier in FR1 can use 15 kHz SCS for a 20 MHz bandwidth, while a carrier in FR2 would typically use 120 kHz SCS for a 100 MHz bandwidth. The UE's capability signaling to the network includes which FRs and specific bands within them it supports. The network uses this information during initial cell selection, handover, and carrier aggregation. Crucially, carrier aggregation and dual connectivity can occur within a single FR (intra-FR) or between different FRs (inter-FR), with the latter requiring the UE to support multiple RF chains and potentially different timing relationships. The FR definition thus provides a structured framework that scales the NR design from low-band wide coverage to high-band extreme capacity, ensuring global interoperability while allowing optimized implementations for different spectrum regimes.

Purpose & Motivation

The concept of Frequency Ranges was formally introduced in 3GPP to provide a scalable and organized framework for the expansive spectrum landscape addressed by 5G NR. Prior to NR, LTE bands were defined individually with specific requirements, but the unprecedented breadth of spectrum considered for 5G—from below 1 GHz to above 50 GHz—necessitated a higher-level grouping. The purpose was to cluster bands with similar propagation characteristics and technical challenges, allowing for a more efficient specification of common RF and physical layer parameters. This solved the problem of having to redundantly define the same set of requirements for dozens of individual bands that shared fundamental properties.

Historically, the motivation stemmed from the need to clearly separate the design considerations for 'sub-6 GHz' spectrum (with characteristics similar to existing 4G) from 'mmWave' spectrum (which introduced new challenges like high path loss, beam-based operation, and wider bandwidths). Creating FR1 and FR2 allowed 3GPP to tailor core aspects of the NR standard: FR1 specifications focus on wide-area coverage, mobility, and backward coexistence with LTE, while FR2 specifications mandate features like analog beamforming, beam failure recovery, and specific RF requirements for power density. This division addresses the practical limitations of a one-size-fits-all approach, enabling device and infrastructure manufacturers to optimize their designs for specific frequency regimes. It also simplifies network deployment and operation by providing clear guidelines on what capabilities and configurations are applicable in a given block of spectrum.