Most high-priority users operate continuously at a well-known location. However, Naval radar operations can happen at different places and different times.

In order to maximize the amount of spectrum available for commercial use, the SAS uses specialized sensors (ESCs) to detect when and where the Navy is using the band. When they use the band, the SAS must adjust the operation of the CBSDs under its control to ensure that they do not disrupt the Navy’s operations.

In particular, when the SAS learns that incumbent activity has been detected in a Dynamic Protected Area (DPA), it activates protections for that DPA. When a DPA is activated, all grants that cause too much interference to Navy operations are suspended.

The SAS uses a DPA move list to keep track of which grants must be suspended during incumbent activity. As the following table shows, the grant only needs to be suspended if it’s on the move list and incumbent activity is detected.

 Grant is on the move list Grant is not on the move list
DPA is active SuspendedNot suspended
DPA is not activeNot suspendedNot suspended

When a grant is added to a move list

Each night the SAS recalculates which grants must be suspended during incumbent activity and updates its DPA move lists.

It does this by ranking all grants on the corresponding channel according to the interference they would cause to the DPA. It removes as many low-interference grants as possible from the move list, but must add the remaining higher-interference grants to the move list. This means that a grant’s membership on the move list is determined both by its own characteristics and by the characteristics of other nearby grants.

During the day, all new grants which may impact the DPA must be added to the move list. A grant is considered to potentially impact a DPA if it is in that DPA’s neighborhood. As a general rule of thumb, neighborhoods have the following approximate sizes:

  • Category A CBSD: 150 km
  • Category B CBSD:
    • West coast: 150-200 km
    • East coast: 300-400 km
    • Gulf coast: 300-400 km