How to Plan for DPA Activation

This guide explains what happens during a Dynamic Protection Area (DPA) activation and how to prepare your CBSD deployment to minimize or eliminate disruption.

Overview

A DPA (Dynamic Protection Area) is a geographic zone around federal radar systems (primarily coastal shipborne radars). When an ESC sensor detects radar activity (or portal notification occurs), the DPA is activated on specific channels.

During activation:

• SAS commands affected CBSDs to suspend, reduce power, or terminate grants on protected channels
• Goal: Zero harmful interference to federal radars

Key Bridge SAS Note: We protect DPAs conservatively but efficiently. Activations are channel-specific and temporary — channels often return quickly after radar activity ends. If we can keep you online with an alternate solution (e.g., reduced EIRP via dynamic parameter recommendation), we'll try.

User Impact

From your radio/CBSD perspective:

• Heartbeat responses transition to SUSPENDED_GRANT (500) for affected grants (Heartbeat responses do NOT transition to TERMINATED_GRANT)
• Key Bridge proprietary: We add a reason to the responseMessage and message data fields (e.g., "DPA activation - coastal radar detected")
• Dynamic parameter recommendations may reduce EIRP
• Transmission must stop immediately on impacted channels
• Other grants (non-affected channels) remain active

Disruption Level:

• Significant if relying on single grant in lower/mid band
• Minimal or zero with proper planning

What to Do When a DPA is Activated

1. Fall-Back Immediately

   • Stop transmission on the affected 10 MHz channel(s)
   • Adjust your traffic to your other active grants
   • Use multi-grant failover logic to switch seamlessly

2. Wait for Clearance

   • The activated channel will typically clear in about two hours
   • Continue heartbeats on suspended grants — they may resume automatically

3. Monitor for Extended Events

   • If the channel is still occupied after 8 to 12 hours, an extended event is occurring
   • These can sometimes last for a few days (e.g., naval exercises)

Key Bridge Customers Only
You can manually check the current DPA activation status on our CBRS portal:
https://keybridgewireless.com/cbrs

The portal shows:

• Active DPAs
• Affected channels
• Neighborhood boundaries
• Estimated clearance times (when available)

How to Plan and Minimize Disruption

1. Use Multi-Grant Strategies

   • Maintain multiple concurrent 10 MHz grants (3–15 allowed)
   • Critical: Always include at least one grant in the upper 50 MHz (3650–3700 MHz)
   • Reason: Most DPA activations protect lower channels first; upper band often remains available longer

2. Spread Grants Across the Band

   • Request full band initially — SAS assigns diverse channels
   • Target lower, mid, and upper segments

3. Enable Grouping and Measurements

   • Consistent groupingParam + received power reports
   • Helps SAS keep you on air with adjusted parameters when possible

4. Robust Heartbeat Handling

   • On 500 SUSPENDED_GRANT: Immediately stop transmitting on that channel; continue heartbeats (may resume)
   • Detect dynamic parameter recommendations → request new grant promptly

5. Operational Tips

   • Use radio features for seamless channel switch (make-before-break)
   • Persist grant state for quick recovery
   • Monitor for patterns (e.g., frequent coastal activations)

Best Practices Summary

Result: Well-planned deployments typically experience little to no service interruption during DPA activations.

Next Steps

• Review your grant distribution — ensure upper 50 MHz coverage
• Implement automated channel failover
• Bookmark the CBRS portal DPA status page for quick checks