The Spectrum Access System (SAS) is a cloud-based service that manages the wireless communications of devices transmitting in the CBRS band, in order to prevent harmful interference to higher priority users.
How CBSDs communicate with the SAS
The SAS-CBSD API defines six methods that a CBSD can use to communicate with a SAS.
- Registration: The CBSD tells the SAS critical details about itself and receives a unique identifier from the SAS. Learn more about registration.
- Spectrum inquiry: The CBSD’s mechanism for learning what spectrum is available given its location and installation characteristics. Learn more about spectrum inquiry.
- Grant requests: CBSDs request a grant to reserve a portion of the spectrum for their use. If approved, the reservation has been made but the CBSD is not yet authorized to transmit using the grant. Learn more about how to request a grant.
- Heartbeat requests: CBSDs periodically send heartbeat requests for each of their approved grants in order to receive authorization to transmit. Learn more about heartbeat requests.
- Relinquish a grant: When the CBSD no longer wishes to use a grant, it relinquishes the grant. Learn more about how to relinquish a grant.
- Deregistration: If the CBSD is decommissioned or moved, it deregisters from the SAS. Learn more about deregistration.
How the SAS protects higher-priority users
To make sure that higher priority users are protected, the SAS communicates with CBSDs and performs activities, like:
- To protect the highest-priority users, Naval radar operators, the SAS uses a sensor network of sensors to detect when they're using the spectrum. This means that sometimes, some portions of the CBRS spectrum is unavailable in regions near the coast. Learn more about deployment availability.
- Every night, all SASes execute a process called Coordinated Periodic Activities among SASes (CPAS) to make sure that they're operating with the latest information. Learn more about CPAS and what it means to CBSDs operators.