5G NR Operating Frequency & Band Identifier

Architecture of 5G Spectrum: FR1 vs. FR2 Operational Dynamics

The 3rd Generation Partnership Project (3GPP) specifications TS 38.101-1 and TS 38.101-2 classify all cellular radio frequency spectrum allocated for 5G New Radio into two fundamental physical frequency ranges: Frequency Range 1 (FR1) spanning 410 MHz to 7125 MHz (often termed "Sub-7 GHz"), and Frequency Range 2 (FR2) spanning 24.25 GHz to 71.0 GHz (termed "Millimeter-Wave" or mmWave). FR2 is further subdivided into FR2-1 (24.25 GHz – 52.6 GHz) and FR2-2 (52.6 GHz – 71.0 GHz).

These two frequency domains exhibit profoundly divergent RF propagation physics, RF front-end architectures, and air-interface numerologies:

• FR1 Sub-1 GHz Coverage Layers (e.g., Bands n5, n8, n12, n20, n28, n71): Characterized by low free-space path loss (FSPL), deep non-line-of-sight (NLOS) penetration through reinforced concrete, and minimal atmospheric attenuation. These bands form the macro-cellular umbrella coverage layer, enabling nationwide 5G reach and rural connectivity. However, spectrum allocations are narrow (typically 5 MHz to 20 MHz per operator), necessitating aggressive spectral efficiency optimization.
• FR1 Mid-Band Capacity Layers (e.g., Bands n1, n3, n7, n40, n41, n77, n78): The international sweet spot for 5G eMBB (Enhanced Mobile Broadband). Specifically, the 3.3 GHz to 4.2 GHz C-Band (Bands n77 and n78) and 2.5 GHz (Band n41) combine favorable propagation with wide contiguous channel bandwidths (up to 100 MHz per carrier). This frequency regime allows the practical physical implementation of massive Active Antenna Units (AAUs) with 32T32R or 64T64R cross-polarized antenna elements within manageable physical dimensions.
• FR2 Millimeter-Wave Hotspot Layers (e.g., Bands n257, n258, n260, n261): Characterized by extreme free-space path loss, severe oxygen absorption (peaking at 60 GHz), high rain fade, and near-total penetration blockage by human bodies and low-emissivity building glass. To counteract this attenuation, mmWave radios utilize massive phased-array beamforming with narrow pencil beams, providing massive component carrier bandwidths of 50 MHz, 100 MHz, 200 MHz, and 400 MHz for multi-gigabit throughput in dense urban stadiums, train stations, and fixed wireless access (FWA) deployments.

Duplex Topologies: FDD, TDD, SDL, and SUL Mechanics

In 3GPP 5G NR network dimensioning, operating bands are categorized under four distinct duplex architectures:

1. Time Division Duplexing (TDD)

In TDD bands (e.g., n41, n77, n78, and all FR2 mmWave bands), uplink (UL) and downlink (DL) share the exact same RF frequency allocation (F_UL = F_DL) separated exclusively in the time domain by slot formatting. TDD provides two foundational advantages for 5G:

• Channel Reciprocity: Because uplink and downlink signals travel through identical multipath channels at virtually the same instant, the base station (gNodeB) can measure the user equipment's (UE) Sounding Reference Signal (SRS) on the uplink to accurately determine the downlink channel state. This enables closed-loop massive MIMO beamforming weight calculations without requiring complex, bandwidth-consuming CSI feedback codebooks from the UE.
• Dynamic Uplink-Downlink Adaptation: Operators can tailor time-domain slot splits (e.g., DDDSU vs. DSUUD) to match asymmetric consumer traffic demands (typically 75% to 80% downlink-heavy).

2. Frequency Division Duplexing (FDD)

In FDD bands (e.g., n1, n3, n7, n28), uplink and downlink operate concurrently on separate, paired frequency slices separated by a fixed duplex spacing (ΔF_duplex):

Because downlink and uplink transmit simultaneously 100% of the time, FDD provides continuous coverage and eliminates TDD guard periods. However, the distinct uplink and downlink frequencies preclude reciprocity-based beamforming, requiring explicit codebook feedback.

3. Supplementary Uplink (SUL) and Supplementary Downlink (SDL)

In 5G NR, high-frequency TDD carriers suffer from an inherent link-budget imbalance: while high-power gNodeBs (200W+) can push downlink signals over several kilometers, mobile UEs are battery-limited to a maximum transmit power of 23 dBm (200 mW) or 26 dBm (400 mW for Power Class 2). Consequently, user equipment experiences uplink cell-edge starvation long before downlink coverage fails.

To resolve this, 3GPP introduced Supplementary Uplink (SUL) (e.g., Bands n80, n81, n82, n83, n84) and Supplementary Downlink (SDL) (e.g., Bands n75, n76). Through SUL, a UE receiving high-speed downlink data on a mid-band TDD carrier (e.g., n78 at 3.5 GHz) dynamically switches its uplink transmission to a low-frequency SUL carrier (e.g., n80 at 1.8 GHz or n83 at 700 MHz). This decouples UL and DL, expanding cell-edge coverage radius by up to 200% while maintaining gigabit downlink speeds.

Global Harmonization of C-Band (Bands n77 & n78)

Bands n77 and n78 constitute the industrial anchor of global 5G rollouts. Band n78 (3300 MHz to 3800 MHz) is universally harmonized across the European Union, the United Kingdom, Japan, South Korea, Australia, and China, serving as the international baseline for 5G consumer devices.

Band n77 (3300 MHz to 4200 MHz) is a superset of Band n78 that incorporates 400 MHz of additional spectrum up to 4.2 GHz. In the United States, the Federal Communications Commission (FCC) auctioned 280 MHz of C-Band spectrum (3700 MHz to 3980 MHz) under Band n77, accompanied by the Citizens Broadband Radio Service (CBRS / Band n48) at 3550 MHz to 3700 MHz.

To prevent inter-service interference with legacy airborne radio altimeters operating in the 4200 MHz to 4400 MHz band, aviation safety regulators mandated a minimum 220 MHz safety guardband (capping commercial US C-Band deployments at 3980 MHz) alongside restricted antenna tilt angles near airport runway approaches.

3GPP 5G NR Operating Bands Reference Table (TS 38.101-1 / TS 38.101-2)

The table below indexes standardized 3GPP 5G New Radio operating frequency bands across FR1 Sub-7 GHz and FR2 Millimeter-Wave, detailing duplex schemes, uplink/downlink allocations, duplex spacing, and industry nomenclature: