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How CBRS 2.0 is Driving the Future of Private Cellular Networks

CBRS 2.0

Approved in 2020 by the Federal Communications Commission (FCC), the Citizens Broadband Radio Service (CBRS) introduced an innovative framework for sharing previously restricted spectrum (3550 to 3700 MHz) in the 3.5 GHz band. While CBRS enabled many new opportunities for private cellular network deployments, several real-world constraints limited mass adoption. These included Dynamic Protection Area (DPA) models with sweeping exclusion zones, 15-minute heartbeat intervals, and General Authorized Access (GAA) coexistence challenges such as interference and, at times, suboptimal spectrum allocation.

CBRS 2.0 addresses these issues with significant technical improvements. New DPA models incorporate realistic environmental parameters, effectively reducing exclusion zones and enabling denser deployments. Additionally, heartbeats now occur once every 24 hours, optimizing network management and minimizing the risk of service interruptions. Lastly, GAA coexistence mechanisms ensure efficient spectrum sharing and help mitigate interference.

Expanding Uninterrupted CBRS Coverage
DPAs protect incumbent users while allowing mobile network operators (MNOs), private network operators, and public safety networks to access CBRS spectrum shared with the U.S. Department of Defense (DoD). Initially, these exclusion zones restricted spectrum use over wide coastal and inland areas. New CBRS 2.0 regulations, however, provide up to 90% more availability for non-incumbent users in many deployment scenarios.

CBRS 2.0 Coverage

Figure 1. Comparison of protection zones for CBRS devices under 6 meters for indoor deployments before (purple) and after (white) the implementation of CBRS 2.0. New CBRS 2.0 regulations significantly reduce these protection zones, enabling expanded coverage and improved performance. (Source: OnGoAlliance)

Although DPA reduction positively impacts all Citizens Broadband Radio Service Devices (CBSDs), Category A and Category B devices, which include small cells and Fixed Wireless Access (FWA) systems, at and below 6 meters above ground level (AGL) significantly benefit from improved propagation models. Category A devices are deployed indoors with a maximum equivalent isotropic radiated power (EIRP) of 30 dBm while Category B equipment have a higher maximum EIRP of 47 dBm and are deployed outdoors.

These new CBRS 2.0 propagation models incorporate detailed environmental parameters for buildings and foliage, enabling more accurate interference calculations and spectrum management. Key parameters include a clutter factor for CBSDs at and below 6 meters, an indoor-outdoor factor of 15 dB for all indoor CBSDs regardless of height, and an 8 dB activity factor for all CBSDs, combining an 80% Time Division Duplex (TDD) configuration and 20% loading factor.

CBRS 2.0 DPA Reduction

Figure 2. A detailed chart illustrating the reduction in DPA neighborhood areas for different CBSD categories under new FCC regulations. The chart highlights the additional loss in propagation models for each category. (Source: OnGoAlliance)

The revised regulations and technical upgrades of CBRS 2.0 expands coverage for an additional 72 million people in over a dozen states. Additionally, CBRS 2.0 increases the geographic area unaffected by DPA disruptions from 78% to 97% of the total U.S. landmass.

Reducing Heartbeat Intervals and Improving GAA Co-Existence
CBRS 2.0 allows CBSDs outside of reduced protection areas to operate for up to 24 hours without reauthorization from the Spectrum Access System (SAS). While most operators will reauthorize every six hours, extending heartbeat intervals from 5 minutes to 24 hours reduces the risk of service interruptions and significantly increases reliability. These periodic signals, sent by CBSDs to the SAS, confirm operational status and maintain spectrum grants and access. Notably, an extended operational window bolsters network stability, particularly for deployments with intermittent connectivity.

Lastly, CBRS 2.0 introduces an optional coexistence mechanism that helps the SAS enforce frequency planning across CBSDs in coordination with GAA operators. This mechanism bolsters reliable access for enterprises and FWA providers using CBRS GAA, efficiently mitigating interference without overly limiting GAA operations. By dynamically adjusting operational parameters based on real-time conditions, the SAS ensures effective CBRS GAA spectrum use and reduces the risk of conflicts between GAA users.

Conclusion
Over the past four years, more than 1,000 CBRS operators have deployed nearly 400,000 broadband APs nationwide. Reduced DPA zones, infrequent heartbeats, and optimized GAA coexistence techniques will further improve CBRS spectrum management, reliability, and operational efficiency. As CBRS 2.0 rolls out, we expect to see private cellular network deployments increase across wider geographic areas with these improvements helping to drive adoption. Industry 4.0, healthcare, and emergency response communications are likely to be among the first mission-critical private network applications to take full advantage of the new CBRS capabilities.

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