Frequency Range 1

Description

Frequency Range 1 (FR1) is one of the two frequency ranges defined for 5G New Radio (NR) in 3GPP specifications. As per TS 38.101-1, FR1 encompasses the spectrum from 410 MHz to 7125 MHz, which includes many legacy bands used by 2G, 3G, and 4G, as well as new bands allocated for 5G. FR1 is often referred to as the sub-6 GHz range, although it extends slightly above 6 GHz to 7.125 GHz. This range is crucial for providing wide-area coverage and is the primary band for initial 5G deployments, offering a balance between capacity and coverage.

FR1 supports flexible numerology, with subcarrier spacings (SCS) of 15, 30, and 60 kHz. The choice of SCS depends on the deployment scenario and the trade-off between latency, coverage, and mobility support. For example, 15 kHz SCS is used for wide-area coverage, while 60 kHz SCS is used for low-latency applications. FR1 operates in both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes, allowing operators to use their existing spectrum assets efficiently. The maximum channel bandwidth in FR1 is 100 MHz per carrier, which can be aggregated for higher data rates.

The physical layer design for FR1 includes support for massive MIMO, beamforming, and advanced modulation schemes such as 256-QAM. These features enable high spectral efficiency and throughput. FR1 also supports dynamic spectrum sharing (DSS) with LTE, allowing operators to deploy 5G NR in existing LTE bands without refarming spectrum. This is achieved through careful coordination of reference signals and scheduling between the two technologies.

In terms of architecture, FR1 is used by both the gNodeB (gNB) and the User Equipment (UE). The gNB transmits synchronization signals (SSB) and system information in FR1, and the UE performs cell search and random access accordingly. The smaller propagation loss in FR1 compared to FR2 (mmWave) allows for better coverage and penetration, making it suitable for rural and suburban areas as well as urban macrocells. However, the available bandwidth is limited compared to FR2, which can impact peak data rates.

FR1 is integral to the 5G system, providing the coverage layer that complements the capacity layer of FR2. It supports all 5G services, including enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communication (URLLC), and massive Machine-Type Communication (mMTC). The specifications for FR1 are continuously evolving, with new bands and features added in each release to improve performance and efficiency.

Purpose & Motivation

Frequency Range 1 (FR1) was defined to provide a dedicated spectrum range for 5G NR that balances coverage and capacity. Before 5G, cellular systems operated in various bands below 6 GHz, but they lacked a unified framework for flexible numerology and wide bandwidths. FR1 addresses this by defining a common set of parameters and requirements for sub-6 GHz operation, enabling global harmonization and economies of scale. It allows operators to reuse existing spectrum and infrastructure, facilitating faster 5G rollouts.

The primary motivation for FR1 was to ensure wide-area coverage for 5G services, as higher frequency bands (FR2) have limited propagation and are more suitable for dense urban hotspots. FR1 provides the necessary coverage for mobile broadband, IoT, and critical communications. It also supports features like dynamic spectrum sharing, which allows 5G and LTE to coexist in the same band, easing the transition for operators.

FR1 solves the problem of spectrum fragmentation by defining a flexible framework that can accommodate various channel bandwidths and duplex modes. It enables the use of advanced antenna techniques and high-order modulation, improving spectral efficiency. The definition of FR1 in 3GPP specifications ensures interoperability between vendors and allows UEs to support multiple bands within FR1, enhancing global roaming. Overall, FR1 is foundational to 5G, providing the coverage layer that makes ubiquitous 5G services possible.