Frequency Range 2

Description

Frequency Range 2 (FR2) is the millimeter-wave (mmWave) frequency range defined for 5G New Radio (NR) in 3GPP specifications. As per TS 38.101-2, FR2 spans from 24.25 GHz to 71 GHz, although the initial focus was on bands around 28 GHz and 39 GHz. FR2 provides significantly larger bandwidths compared to FR1, enabling multi-gigabit peak data rates and ultra-low latency. However, the propagation characteristics at these frequencies result in higher path loss, poor penetration through obstacles, and limited coverage, necessitating dense small-cell deployments and advanced beamforming techniques.

FR2 supports subcarrier spacings of 60, 120, and 240 kHz, which are larger than those in FR1 to combat phase noise and support wider bandwidths. The maximum channel bandwidth in FR2 is 400 MHz per carrier, and with carrier aggregation, even higher bandwidths can be achieved. FR2 operates primarily in TDD mode due to the difficulty of implementing FDD at mmWave frequencies. The use of massive MIMO and beamforming is essential in FR2 to overcome high path loss; the gNB and UE use phased array antennas to steer beams and maintain link budget.

The physical layer design for FR2 includes support for flexible beam management, beam failure recovery, and multi-beam operation. Synchronization signals and system information are transmitted via beams, and the UE performs beam sweeping during initial access. FR2 also supports dual connectivity with FR1 (EN-DC or NR-DC), where FR1 provides the coverage layer and FR2 provides the capacity layer. This architecture allows seamless mobility and service continuity.

In terms of deployment, FR2 is typically used in dense urban areas, stadiums, and hotspots where high capacity is needed. The small coverage radius of FR2 cells (often less than 200 meters) requires a dense network of small cells, which increases deployment costs. However, the large bandwidths available in FR2 make it ideal for fixed wireless access (FWA) and high-speed backhaul. FR2 also supports advanced features like integrated access and backhaul (IAB) to reduce fiber deployment costs.

FR2 is a key enabler for the most demanding 5G use cases, such as ultra-high-definition video streaming, virtual reality, and industrial automation. Its specifications continue to evolve, with new bands and features added in each release to improve spectral efficiency and coverage. Despite its challenges, FR2 is essential for delivering the extreme capacity and low latency promised by 5G.

Purpose & Motivation

Frequency Range 2 (FR2) was defined to unlock the vast spectrum available at millimeter-wave frequencies for 5G NR. Before 5G, cellular systems were confined to sub-6 GHz bands, which offered limited bandwidth and could not support the multi-gigabit data rates envisioned for 5G. FR2 addresses this by providing a framework for operating in the 24.25–71 GHz range, where large contiguous bandwidths are available. This enables extreme capacity and low latency, making it suitable for dense urban hotspots and specialized applications.

The motivation for FR2 was to meet the International Mobile Telecommunications (IMT)-2020 requirements for peak data rates (20 Gbps) and user-experienced data rates (100 Mbps). FR1 alone cannot achieve these targets due to spectrum scarcity. FR2 also supports new use cases like fixed wireless access and industrial IoT, where high throughput and low latency are critical. However, the propagation challenges of mmWave required innovative solutions like beamforming and dense small cells, which are integral to FR2 specifications.

FR2 solves the problem of spectrum shortage by opening up new bands for mobile communications. It also drives innovation in antenna technology and network architecture. The definition of FR2 in 3GPP ensures global harmonization and interoperability, allowing UEs to roam across different FR2 deployments. While FR2 deployments are still growing, it is a cornerstone of the 5G vision for ubiquitous high-speed connectivity.