Geo-Location Database

The database stores geometrically defined exclusion zones around primary user receivers, calculated using propagation models (e.g., Longley-Rice, ITU-R P.1546) that account for terrain, antenna height, and transmit power. These contours establish the geographic area where secondary transmissions are prohibited or power-limited to prevent harmful interference. For example, a TV broadcaster's protected contour extends to the Grade B signal level (typically 41 dBμV/m), and the database enforces a keep-out distance plus an additional separation margin to account for aggregate interference from multiple secondary devices.

Secondary devices (e.g., TV White Space radios, CBRS Citizens Broadband Radio Service Devices) must query the database before transmitting. The query includes the device's geolocation (derived from GPS or an installed location), antenna height above ground, and device class. The database responds with a channel availability map and maximum permissible Effective Isotropic Radiated Power (EIRP) for each available channel. This response is time-limited (typically a validity period of 24 hours for fixed devices, shorter for mobile), after which the device must re-query to ensure continued protection of incumbents.

Geo-location databases enforce a strict priority hierarchy among spectrum users. In the CBRS three-tier model, Incumbent Access (Tier 1) users—such as naval radar and fixed satellite service earth stations—receive absolute protection. Priority Access Licensees (Tier 2) receive interference protection from General Authorized Access (Tier 3) users but must yield to incumbents. The database dynamically reallocates channels, instructing lower-tier devices to vacate frequencies when a higher-tier user activates within their geographic area. This is managed through suspension orders or updated spectrum inquiry responses.

The database does not rely on real-time sensing but on computationally intensive propagation modeling to predict interference. It integrates digital terrain elevation data, clutter models (land use/land cover classifications), and building penetration loss estimates. For incumbent protection, the model calculates the path loss from every potential secondary transmitter location to the incumbent receiver, ensuring the aggregate interference-plus-noise floor remains below the protection criteria. This deterministic approach provides predictable, regulator-approved protection without the hidden node problem inherent in spectrum sensing.

Multiple database providers may be authorized by a regulator (e.g., FCC-approved SAS Administrators), requiring strict data synchronization to ensure consistent protection decisions. All providers ingest the same incumbent registration data and must implement identical propagation algorithms. When one database authorizes a secondary transmission, it records the grant details (frequency, power, location, time) in a shared repository. Other databases consult this record to account for aggregate interference from devices they do not directly manage, preventing the tragedy of the commons in shared spectrum bands.

While fixed devices query the database directly via internet connection, Mode II personal/portable devices (which can initiate a network) must also query the database using their own geolocation. Mode I devices (client-only, under control of a Mode II or fixed device) receive operational parameters from their master device. For mobile operation, the database may return a channel validity map that defines a geographic polygon within which the granted parameters remain valid, enabling limited mobility without constant re-querying. Exiting this polygon triggers a mandatory new query before further transmission.

The original regulatory use case for geo-location database access. Unlicensed devices operating in unused broadcast television spectrum (VHF/UHF) must query a certified database to determine available channels and maximum permissible EIRP limits at their location.

• Protects incumbent broadcast contours and wireless microphones
• Database calculates co-channel and adjacent-channel protection
• Devices must re-check availability every 60 seconds per FCC rules

The geospatial propagation models stored within the geo-location database that define the protected service area around each primary user. These contours are calculated using terrain-aware path loss models like Longley-Rice (ITS) or Hata-Davidson to determine where secondary transmissions would exceed harmful interference thresholds.

• Includes fade margin for temporal signal variability
• Defines keep-out distances for mobile secondary devices
• Updated when incumbents register new operational parameters

A regulatory mandate requiring 5 GHz unlicensed devices to detect radar signals and vacate channels, often implemented via a geo-location database lookup rather than active sensing. The database stores FCC-mandated terminal Doppler weather radar (TDWR) locations and frequencies.

• Required for UNII-2 and UNII-2e band operation
• Channel availability check must complete before transmission
• 30-minute non-occupancy period after radar detection

A European regulatory framework distinct from CBRS that uses a geo-location database to grant controlled secondary access under individual licenses. Unlike the three-tier model, LSA establishes a bilateral agreement between an incumbent and a limited number of secondary licensees with well-defined geographic and temporal constraints.

• Deployed in the 2.3 GHz band across multiple EU member states
• Provides guaranteed quality of service unlike opportunistic access
• Repository stores license terms alongside propagation models

The computational core of any geo-location database that translates incumbent transmitter parameters into protected contours. These engines ingest digital terrain elevation data (DTED), clutter models, and atmospheric refractivity to calculate path loss using irregular terrain models.

• Longley-Rice (ITM) is the FCC-preferred model for TVWS
• eHata used for CBRS below 1.5 km antenna height
• Must account for building penetration loss in urban environments