Grant Suspension and Recovery Procedures

Temporary Protection. Rapid Recovery for Maximum Uptime

Version 1.0 | For CBSD operators, network planners, and integration teams

Key Bridge SAS applies grant suspension to protect incumbent users from harmful interference. Suspension is a temporary state — it does not terminate or cancel a grant.

This document explains how Key Bridge manages grant suspensions and recoveries so that CBSD operators can understand our approach and correctly interpret SAS responses.

When Grants Are Suspended

Key Bridge may return a grant in Suspended status when the following conditions exist:

• The proposed CBSD operation would exceed the allowed interference threshold to a protected entity.
• A protected entity becomes active in the same area and frequency range as an existing grant.
• Calculated interference at a protected receiver exceeds the defined protection limit.

In every case, suspension is applied only when necessary to safeguard incumbents. The grant retains its original grant ID and remains valid for future use once the condition is resolved.

How Key Bridge Handles Suspensions

Key Bridge uses two distinct approaches depending on the type of protected entity involved.

DPA-Related Suspensions

• These occur when a Dynamic Protection Area (DPA) is activated in the 3550–3650 MHz band.
• Affected grants are immediately placed into Suspended status to protect the active DPA.
• A protection window (T3) is enforced. During this period, Heartbeat responses include a clear indication that the grant is suspended along with an estimated time until it may become available.
• The CBSD must continue sending Heartbeat requests. Once the DPA constraint is no longer active and the protection window has elapsed, Key Bridge automatically clears the suspension.
• This process ensures strong, predictable protection for high-priority federal systems.

Non-DPA Suspensions

Non-DPA suspensions apply to protected entities such as:

• Priority Access License Protection Areas (PPAs)
• ESC sensors
• Fixed Satellite Service (FSS) sites
• Other designated protection zones

For these cases, Key Bridge uses a proprietary rapid recovery process:

• When a grant is issued in Suspended status due to a non-DPA entity, Key Bridge immediately performs an updated interference analysis.
• If the analysis shows that interference has fallen below the protection threshold, the suspension is cleared automatically.
• In typical conditions, the CBSD will receive confirmation that the grant is no longer suspended within approximately one minute through its next Heartbeat response.
• This approach avoids waiting for the next daily protection calculation cycle, which occurs once every 24 hours.

How Suspended Grants Recover

Not all suspended grants are handled the same way. The time it takes for a grant to return to operational status depends on the type of protected entity that triggered the suspension. The diagram below compares the two primary paths — Non-DPA suspensions (such as PPA, ESC, and FSS) and DPA suspensions — and shows how Key Bridge’s processes differ in each case. This comparison helps explain why some grants recover in approximately one minute while others follow a longer protection timeline.

Key Bridge restores suspended grants using the following mechanisms:

• Rapid interference re-evaluation: Applied immediately for most non-DPA suspensions, enabling recovery in approximately one minute.
• Continuous background monitoring: Ongoing calculations detect when interfering conditions have changed or been removed.
• Heartbeat-based status updates: CBSDs receive current grant status on every Heartbeat. When a suspension is cleared, the next successful Heartbeat response authorizes transmission.
• DPA deactivation handling: When a DPA returns to inactive status, affected grants are reviewed and restored if no other constraints remain.

A suspended grant does not need to be re-requested. The original grant ID remains valid and is restored to operational status once the suspension is lifted.

Recommended Handling of Suspended Grants

When your CBSD receives a grant in Suspended status, the way it responds can significantly impact how quickly service is restored. Many devices incorrectly discard the suspended grant and immediately request a new one. This approach often leads to longer downtime and can result in sub-optimal channel assignments. The diagram below illustrates the recommended behavior: accept the suspended grant, begin heartbeating immediately, and allow Key Bridge’s recovery processes time to clear the suspension.

Do not discard a suspended grant and immediately retry. On the Key Bridge SAS if you wait a minute your suspended grant is likely to clear. We therefore strongly recommend you follow the following procedure.

Strongly Recommended Behavior

Many CBSD implementations incorrectly discard a suspended grant and immediately request a new grant. This approach is inefficient and often counterproductive.

Do not discard a suspended grant and retry.

This behavior can cause the following problems:

• The device enters a retry loop and remains offline for an extended period.
• The CBSD may receive a different (and potentially inferior) channel assignment on the next attempt.
• Unnecessary load is placed on both the CBSD and the SAS.

Correct behavior when your CBSD receives a suspended grant:

• Accept the grant as issued. Do not discard it.
• Immediately begin sending Heartbeat requests against the suspended grant.
• Wait at least two to three Heartbeat cycles before considering any other action. In most non-DPA cases, the suspension will clear within this timeframe due to Key Bridge’s rapid recovery process.
• If desired, inspect the grant response metadata (particularly the responseData field) to understand the specific reason the grant was suspended.

Following this procedure allows the grant the opportunity to transition to operational status quickly and avoids the risks associated with unnecessary retries.

What CBSD Operators Should Expect

• A Suspended grant response will still include a valid grantId.
• Heartbeat responses will clearly indicate Suspended status while the condition exists.
• For most non-DPA suspensions, Key Bridge’s rapid recovery process allows the grant to return to normal operation within approximately one minute when the CBSD follows the recommended handling procedure above.
• For DPA-related suspensions, Heartbeat responses include timing guidance so operators know when the grant is expected to become available.
• Once cleared, the grant resumes normal operation without requiring a new grant request (subject to standard Heartbeat and renewal rules).
• Suspension status is always communicated transparently through standard SAS responses.

Key Benefits of Key Bridge’s Approach

• Strong, reliable protection is maintained for all incumbent users at all times.
• Most non-DPA suspensions are resolved in approximately one minute instead of up to 24 hours when the recommended handling procedure is followed.
• Grant IDs remain stable — suspension does not invalidate or cancel the grant.
• CBSDs receive clear, actionable status information through normal Heartbeat responses.
• The entire process is automated and requires no manual action from the CBSD operator when the recommended behavior is followed.
• The approach balances incumbent protection with efficient spectrum utilization for CBSDs.

Summary

Key Bridge SAS applies grant suspension only when required to protect incumbents. For the majority of cases involving non-DPA protected entities, our rapid recovery process enables most suspensions to be cleared within approximately one minute — provided the CBSD accepts the grant and begins heartbeating as recommended.

DPA-related suspensions follow a structured protection process with clear timing information provided via Heartbeat responses. In all situations, suspended grants retain their identity and are restored automatically as soon as conditions safely allow.

CBSDs that follow the recommended handling procedure (accept the grant and heartbeat) will experience the fastest and most reliable recovery.

Questions? Contact us