CBRS Band Subcarrier Spacing Demystified: How Numerology Shapes 5G Performance
Introduction
Not all subcarriers in 5G are created equal. Beyond the popular discussions about latency, coverage, and spectral efficiency, subcarrier spacing (SCS) stands out as a subtle but powerful factor. SCS is the “numerology” of wireless communications—selecting the best subcarrier spacing is often critical for successful deployments. Let’s explore this concept further.
What is Subcarrier Spacing?
Subcarrier spacing describes the frequency gap between neighboring subcarriers in an OFDM (Orthogonal Frequency Division Multiplexing) signal. In 5G NR (New Radio), there isn’t a single fixed value—instead, the system offers multiple subcarrier spacing options to flexibly address different deployment needs.
CBRS Band as an example
3GPP New Radio (NR) numerology for both n48 (3550–3700 MHz, CBRS) and n77 (3300–4200 MHz, C-band) is standardized for Frequency Range 1 (FR1), which covers 450 MHz to 7125 MHz.
Numerology (Subcarrier Spacing) Support
3GPP Reference: See 3GPP TS 38.104 and TS 38.101-1 (also available via ETSI as ETSI TS 138 104 and 138 101-1).
Supported Subcarrier Spacing (SCS):
For n48 and n77 in FR1, the standardized subcarrier spacings are 15 kHz, 30 kHz, and 60 kHz.
15 kHz and 30 kHz SCS are most commonly deployed; 60 kHz SCS is supported for higher capacity and low latency (Ultra Reliable Low Latency Communication Use Case), but it is less common in practical deployments.
Bands and Channel Bandwidths
n77 Band: 3.3 GHz – 4.2 GHz, channel bandwidths up to 100 MHz, with all above SCS options usable.
n48 Band: 3550 MHz –3700 MHz, same numerology and channel bandwidth logic applies (up to 100 MHz).
Both n48 (CBRS, 3550–3700 MHz) and n77 (C-band, 3300–4200 MHz) are FR1 5G NR bands standardized by 3GPP. For these mid-band frequencies, 3GPP supports multiple numerologies: 15 kHz, 30 kHz, and 60 kHz subcarrier spacing (SCS), as detailed in TS 38.104 and TS 38.101-1.
NR Subcarrier Spacing Table (5G Numerology)
Why Numerology Matters?
Choosing the right SCS isn’t just a technical checkbox—it’s a strategic decision:
• Latency-sensitive apps (remote surgery, factory automation or industrial robotics) demand higher SCS.
• Coverage-first deployments (like rural broadband or disaster recovery) lean on lower SCS.
• Spectrum reuse and interference management hinge on matching SCS to cell size and frequency.
Summary
5G allows multi-numerology—meaning different SCS values can coexist. A stadium might use 30 kHz for general traffic and 120 kHz for specific AR experiences. It’s like tuning different instruments in an orchestra to play in harmony.
Subcarrier spacing is the unsung architect of 5G performance. Whether you're optimizing for latency, coverage, or spectral efficiency, understanding numerology helps you design smarter networks—and deliver better user experiences.
