How to Handle CPAS (Cooperative Periodic Activities among SASs)

This guide explains what CPAS is, its impact on your CBRS operations, and how to prepare to minimize disruptions.

Overview

Cooperative Periodic Activities among SASs (CPAS) is a mandatory daily process defined in WINNF-SSC-0008. All SAS providers synchronize data and recalculate spectrum allocations to ensure consistent, fair interference protection across the ecosystem.

During CPAS:

• SASs exchange full activity dumps (CBSDs, grants, PPAs, ESC data)
• Synchronize with FCC/WInnForum databases
• Run pre-IAP filtering and full Interference Analysis Process (IAP)
• Recalculate DPA move lists and grant parameters

This occurs once every 24 hours.

Key Bridge SAS Note: We participate fully in CPAS. Changes take effect gradually, giving time for adjustment.

CPAS Daily Time

Starts at 07:00 AM UTC (about 2:00 AM in the morning Eastern Time (ET))

User Impact

From your radio/CBSD perspective:

• The shared spectrum state is recalculated
• You may become eligible for more spectrum/power (common improvement) or less (if new interference/incumbent activity)
• Existing grants may be suspended, terminated, or receive dynamic parameter recommendations
• New grant opportunities can open

Potential disruptions can be minimal if planned for and significant if not. With good preparation, most users experience little to no downtime; unprepared deployments may see temporary channel loss.

How to Prepare and Minimize Disruption

1. Use Multi-Grant Strategies

   • Maintain 3–15 concurrent 10 MHz grants (Key Bridge limit: 15)
   • Spread across band: include at least one in upper 50 MHz (3650–3700 MHz) for DPA resilience
   • Enables instant failover if one grant terminates

2. Enable Grouping and Measurements

   • Declare consistent groupingParam across devices
   • Always send received power reports (optional but requested)
   • Provides SAS best data → often higher post-CPAS allocations

3. Monitor Heartbeats Closely

   • Detect dynamic parameter recommendations quickly
   • Automate new GrantRequest using recommended params (make-before-break)
   • Never immediately relinquish on recommendation — request new first

4. Implement Robust Recovery

   • Persist cbsdId and grant state
   • Graceful shutdown/relinquish when possible
   • Quick re-request on any termination/suspension

5. Operational Tips

   • Avoid major changes near the CPAS window (early morning ET)
   • Use radio features for seamless channel/power transitions
   • Log CPAS-period changes to identify patterns

Best Practices Summary

Result: With these in place, CPAS typically results in net improvements (more power/spectrum) with minimal or zero disruption.

Next Steps

• Review your current grant strategy — aim for multi-grant
• Enable measurements and grouping if not already
• Test failover logic in sandbox

[Image placeholder: CPAS timeline and multi-grant failover diagram]