Shared Spectrum

Band 48 (CBRS)

Q: How does the CBRS three-tier sharing framework work?

Tier 1 (Incumbent Access) includes military shipborne radar systems and fixed satellite services that have primary rights to the 3.5 GHz band. Tier 2 (Priority Access Licenses, PAL) are 10 MHz blocks auctioned per county, providing interference protection from GAA users. Tier 3 (General Authorized Access, GAA) allows any certified device to transmit up to 30 dBm EIRP without a license, subject to SAS coordination. The Spectrum Access System (SAS), operated by approved administrators (Google, Federated Wireless, CommScope), dynamically manages frequency assignments and power levels to protect incumbents while maximizing spectrum utilization.

Q: What is the maximum transmit power for CBRS devices?

CBRS Citizens Broadband Radio Service Devices (CBSDs) are classified as Category A (indoor, max 30 dBm EIRP, no antenna height restriction indoors) or Category B (outdoor, max 47 dBm EIRP, antenna height up to 6m AGL without additional coordination). GAA Category A devices are the most common for enterprise deployments because they require only SAS registration, not individual FCC licensing. The lower power limits compared to traditional cellular (43-46 dBm per sector) mean CBRS cells are smaller, typically covering 100-300 meters indoors or up to 1 km outdoors.

Q: Why are enterprises deploying private networks on CBRS?

CBRS enables enterprises to deploy LTE or 5G NR networks on their own premises without purchasing traditional spectrum licenses. GAA access is free and immediate, requiring only SAS registration. PAL licenses (10 MHz per county) provide guaranteed interference protection at a fraction of the cost of national spectrum. Use cases include factory floor automation (low-latency M2M), warehouse IoT (real-time asset tracking), venue connectivity (stadiums, convention centers), and campus networks (universities, hospitals). Private CBRS networks offer better security, coverage customization, and latency than Wi-Fi while avoiding the cost and complexity of carrier partnerships.

/band FOR-tee-ayt/ or /see-bee-ar-ess/

A 3GPP TDD band spanning 3550 to 3700 MHz (150 MHz), the FCC's Citizens Broadband Radio Service. CBRS uses a unique three-tier spectrum sharing framework managed by a Spectrum Access System (SAS): Incumbent Access (military radar), Priority Access Licenses (PAL, auctioned), and General Authorized Access (GAA, license-exempt). Enables enterprises to deploy private LTE and 5G NR networks without traditional spectrum licenses, powering factory automation, warehouse IoT, and campus connectivity.

Range: 3550 – 3700 MHz

Duplex: TDD

Access: 3-tier shared (SAS)

Understanding CBRS

CBRS represents a paradigm shift in spectrum management. Rather than auctioning exclusive nationwide licenses for billions of dollars, the FCC created a shared access framework that allows anyone, from large carriers to individual enterprises, to use 3.5 GHz spectrum. The Spectrum Access System dynamically coordinates usage to protect incumbent military radar systems while maximizing commercial utilization. This approach has spawned an entirely new market for private cellular networks.

The three-tier model works like a traffic light system. When military radar is active (detected by Environmental Sensing Capability sensors along coastlines), CBRS devices in affected areas must vacate the frequencies within 300 seconds. PAL holders get priority over GAA users and cannot be preempted by other commercial users. GAA users must accept interference from PAL holders and other GAA users. In practice, incumbent activity is geographically limited (primarily coastal Navy radar), leaving most of the country available for commercial use nearly 100% of the time.

CBRS Power and Coverage Parameters

Maximum EIRP by Device Category:
Category A (indoor): 30 dBm (1 W) EIRP
Category B (outdoor): 47 dBm (50 W) EIRP

Typical Cell Radius:
Cat A indoor: 50–150 m
Cat B outdoor: 300 m – 1 km

PAL License Structure:
10 MHz blocks per county
7 PAL channels (3550–3620 MHz)
10-year license, renewable
FCC Auction 105: $4.6 billion (2020)

GAA Spectrum:
80 MHz (3620–3700 MHz) always available
+ any unused PAL spectrum

CBRS Three-Tier Framework

Tier	User Type	Protection	Power	License
Tier 1 (Incumbent)	Military radar, FSS	Highest (protected from all)	Unrestricted	Federal allocation
Tier 2 (PAL)	Commercial operators	Protected from GAA	Cat A/B limits	Auctioned ($4.6B)
Tier 3 (GAA)	Anyone (enterprise, ISP)	None (best effort)	Cat A/B limits	Free (SAS registration)

Common Questions

Frequently Asked Questions

How does the CBRS three-tier sharing framework work?

Tier 1 (Incumbents: military radar, FSS) have primary rights. Tier 2 (PAL: auctioned 10 MHz county licenses) get interference protection from Tier 3. Tier 3 (GAA: license-exempt) accepts interference from PAL and other GAA. The SAS dynamically manages frequencies and power. Incumbent activity is mainly coastal, leaving most of the US available commercially full-time.

What is the maximum transmit power for CBRS devices?

Category A (indoor): 30 dBm (1 W) EIRP. Category B (outdoor): 47 dBm (50 W) EIRP. Lower power than traditional cellular means smaller cells: 50 to 150 m indoor, 300 m to 1 km outdoor. Cat A devices are most common for enterprise deployments requiring only SAS registration.

Why are enterprises deploying private networks on CBRS?

GAA access is free and immediate. PAL licenses are affordable per-county. Private CBRS networks provide better security, coverage customization, and latency than Wi-Fi without carrier partnerships. Use cases: factory automation, warehouse IoT, stadiums, campus networks, and fixed wireless ISPs.

Related Terms

← Band 41 (2500 MHz) Band 7 (2600 MHz) →

Private Network Components

Waveguide for 3.5 GHz Test Systems

RF Essentials provides precision terminations and custom waveguide assemblies for CBRS and C-band test equipment, including reference loads for small cell validation and antenna measurement systems.

Request a Quote