How to Handle Dynamic Parameter Changes

This guide explains how to respond to SAS-directed changes in operation parameters during heartbeat, as defined in WINNF-TS-0016.

Overview

The SAS can recommend updated operational parameters (e.g., reduced maxEIRP or shifted frequency range) in a HeartbeatResponse to manage interference or protect incumbents.

Important Clarification: The presence of operationParam in a HeartbeatResponse does not modify the existing Grant. Per WINNF-TS-0016, once issued, a Grant’s operating parameters are never changed. Instead, the SAS is providing recommended parameters for the CBSD to request a new Grant.

Key Bridge SAS Note: We frequently use this mechanism to guide CBSDs toward better-fitting parameters without immediately terminating the current Grant. Many users mistakenly assume the Grant must be terminated and re-issued from scratch — this is not required. Following the recommendation promptly (by requesting a new Grant with the suggested parameters) usually allows continued operation with minimal disruption.

When Recommendations Occur

Common triggers:

• Rising aggregate interference
• Nearby incumbent activity
• DPA neighborhood effects

The recommendation appears in:

• Optional operationParam in HeartbeatResponse
• responseCode remains 0 (SUCCESS)

Step 1: Detect Recommendation in HeartbeatResponse

Look for operationParam even on successful responses.

Example Response with Recommended Lower EIRP

{
  "heartbeatResponse": [
    {
      "grantId": "GRANT-789",
      "operationParam": {
        "operationFrequencyRange": { "lowFrequency": 3620000000, "highFrequency": 3630000000 },
        "maxEirp": 25.0   // Recommended reduction from current
      },
      "transmitExpireTime": "2026-01-07T15:00:00Z",
      "heartbeatInterval": 60,
      "response": { "responseCode": 0 }
    }
  ]
}

Step 2: Request a New Grant with Recommended Parameters

• Use the provided operationParam values in a new GrantRequest
• You may keep the current Grant active until the new one is authorized
• Transition smoothly (make-before-break)

Example New GrantRequest

{
  "grantRequest": [
    {
      "cbsdId": "SAS123/CBSD-001",
      "operationParam": {
        "operationFrequencyRange": { "lowFrequency": 3620000000, "highFrequency": 3630000000 },
        "maxEirp": 25.0   // Use recommended value
      }
    }
  ]
}

Step 3: Transition and Clean Up

• Once new Grant is AUTHORIZED via heartbeat → switch transmission
• Relinquish old Grant

Additional Best Practice: DPA Neighborhood Strategy

When operating in or near a Dynamic Protection Area (DPA) neighborhood:

• Always maintain at least one active grant in the upper 50 MHz (3650-3700 MHz)
• Reason: Many coastal/offshore DPAs protect lower channels first during activation
• Upper channels often remain available longer → seamless failover if lower grants terminate

Implementation:

• Prioritize one grant request in 3650-3700 MHz range
• Keep it heartbeating even if lower channels have higher EIRP

Best Practices & Tips

• Log recommended vs current params for diagnostics
• Automate new GrantRequest on detection — minimizes downtime
• Include fresh measurements in the new request
• Combine with multi-grant strategy for redundancy
• Key Bridge SAS: Following recommendations quickly often prevents termination and speeds restoration to higher limits

Common Issues & Troubleshooting

Next Steps

• Update heartbeat handler to detect and act on operationParam
• Implement automated new GrantRequest logic