FCC Approves New ESC Sensors: How to Conduct Spectrum Coexistence Testing for 3.5GHz Devices?

Foreword

On August 27, 2026, the Wireless Telecommunications Bureau and the Office of Engineering and Technology of the Federal Communications Commission (fcc) issued Public Notice DA 26-901 (GN Docket No. 15-319). This officially approved the deployment and coverage plan for new Environmental Sensing Capability (ESC) sensors in the 3.5 GHz band by Key Bridge Wireless, LLC. The plan covers Dynamic Protection Areas (DPAs) No. 28 through 37 in Alaska and requires the ESC operator to operate in coordination with Spectrum Access Systems (SAS) approved by the FCC for commercial deployment.

What Exactly Did the FCC Approve This Time?

This is not a standard certification approval for ordinary mobile phones or Wi-Fi devices, but rather an access license for the operation of the Spectrum Access System. Whether shared spectrum can operate stably still relies on a verifiable and traceable testing mechanism.

What the FCC approved this time is the sensor registration and coverage plan submitted by the ESC operator, rather than issuing a certificate for a specific end-device. The ESC is responsible for sensing the spectrum that needs to be protected, while the SAS is responsible for coordinating the access of shared devices. Before operators can launch commercial services in the protection areas, they must submit a notification to the FCC to confirm that the sensors covering the area have been built and are operating normally, and provide a list of the approved SAS networks they are connected to.

When there are changes in location, configuration, or coverage, the registration information must be continuously updated and relevant materials must be submitted through the FCC's electronic filing system.

How to Conduct Coordinated Testing for DPA and SAS?

For the 3.5 GHz CBRS utilizing a shared access model, whether a device transmits a signal depends on three factors: first, its own power; second, its location; and third, its real-time authorization status.

The DPA is a dynamic area with priority protection, and the SAS is responsible for overall spectrum scheduling. This indicates that testing cannot be limited to traditional RF metrics; it must cover more complex system coordination scenarios.

Testing is not merely confined to measuring transmission metrics inside a shielded box. It also involves verifying whether the sensor coverage meets the standards, whether the transmission of the protection status is accurate and error-free, whether the device's power reduction or transmission suspension commands are effective, and whether the device can maintain a controlled state when communication is interrupted.

Consequently, the scope of the test object expands to the entire link of "Sensor — SAS — Wireless Device."

What Outputs Are Required for Testing and Certification?

Upon delivery of the testing results, four types of records are required:

1. First, the sensor coordinates and coverage calculation results;

2. Second, the messages, timestamps, and reconnection processes between the ESC and the SAS;

3. Third, the specific results of power reduction, transmission suspension, or channel switching after the DPA is activated;

4. Fourth, the impact assessment data following changes in firmware, parameters, and network policies.

Foundational data such as power, spectrum, and spurious emissions are indeed crucial, but whether the system actions are correct must also be documented in a verifiable test report.

The records kept for filing and reference must include not only on-site configuration records but also instrument calibration certificates and software version information. Together, these materials form the complete chain of evidence for compliance, and none of them is dispensable. If any of these are missing, the entire report may lose its credibility, thereby affecting the product's time-to-market.

How Does It Differ from Standard fcc id Testing?

Standard fcc part 15 testing primarily examines the device's transmission and reception performance, out-of-band radiation, and spurious emission levels. The FCC ID is an equipment authorization identifier based on these test results, focusing on the metrics of the product itself.

ESC registration, on the other hand, focuses heavily on shared spectrum protection, coverage area, authorization status, and continuous operation. The two have different purposes and different testing methods, and they cannot replace each other. If enterprises confuse the two, it can easily lead to deviations in testing direction and result in a waste of resources.

Enterprises must first clarify their own role—whether they are an ESC operator, an SAS system, a CBSD wireless device, or an ordinary end-user terminal—and then determine the testing path based on this. If DA 26-901 is misunderstood as "a new fcc certification requirement for all 3.5 GHz products," it will lead to severe misjudgments in the testing scope and budget, and even increase unnecessary costs.

How Should Enterprises Prepare Now?

To initiate preparation work, enterprises can start with the following four steps:

• (1) Clarify the role of the product and the primary entity responsible for it.

• (2) Establish a comprehensive test plan that covers RF metrics, spectrum coexistence, system coordination, and operational records.

• (3) Confirm that the laboratory possesses 3.5 GHz RF testing capabilities as well as system validation capabilities.

• (4) Specifically allocate a change assessment process for firmware upgrades, antenna adjustments, sensor relocations, and changes in network policies. Every step requires meticulous planning to effectively avoid being in a passive position in the future.

The FCC's recent approval update does not set a new threshold for ordinary terminals. Instead, it clearly sends a signal: shared spectrum compliance is shifting from "testing the device" to "verifying how the system operates." Integrating product certification, spectrum coexistence, and operational maintenance into a single, comprehensive schedule will significantly reduce compliance risks for market access in the United States.