Spectrum Inquiry (SIQ) Guide

How Key Bridge Wireless Implements Spectrum Inquiry
and Best Practices for Interpreting and Acting on Our Response

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

Introduction

Spectrum Inquiry is the essential first step for any registered Citizens Broadband Radio Service Device (CBSD) that wants to operate in the 3550–3700 MHz CBRS band. It allows your device to discover which channels are currently available and what maximum transmit power is permitted on each.

At Key Bridge Wireless, we have designed our Spectrum Inquiry service to give you the most useful and reliable answer possible. Our system performs a thorough, multi-layered evaluation that accounts for all current regulatory protections before returning any channels. The goal is simple: deliver a concise list of safe, compliant channels together with accurate power limits so you can make fast, confident decisions and achieve a high grant success rate.

This guide explains, at a conceptual level, how our Spectrum Inquiry process works and provides clear best-practice recommendations for how your CBSD or network management system should consume and act upon the response.

What Spectrum Inquiry Delivers

When you submit a Spectrum Inquiry request, our SAS evaluates your CBSD’s location, registration details, and any measurement reports you include. It then returns a response containing:

A list of available 10 MHz channels that have survived every applicable protection check.
For each channel, the precise maximum Effective Isotropic Radiated Power (EIRP) you may use after all required protections have been applied.
Clear indicators of channel type (PAL or GAA) and any active constraints or reasons why a channel’s power has been reduced or why it has been marked unavailable.

Because we perform the complex intersection of all protection rules on our side, you receive channels that are already safe to request. You do not need to run your own protection calculations or consult external databases.

How We Implement Spectrum Inquiry

Our Spectrum Inquiry process follows a structured, sequential workflow designed to apply every relevant protection rule consistently and fairly.

flowchart TD A[CBSD sends Spectrum Inquiry] --> B[Request Validation & Normalization] B --> C[Incorporate Measurement Data if Available] C --> D[Multi-Stage Protection Evaluation] D --> E[Return Response: Available Channels + Power Limits + Status] style D fill:#e6f3ff,stroke:#0066cc style E fill:#e6ffe6,stroke:#009933

Request Validation and Normalization
Every request is first validated to confirm that the CBSD is properly registered and that the request itself is well-formed. We then normalize the frequency ranges you inquire about onto the standard 10 MHz CBRS channel raster. This step ensures that every channel we evaluate and return corresponds to a valid, usable CBRS channel rather than an arbitrary frequency range.

Incorporation of Measurement Data
When measurement reporting is enabled for your deployment, we accept and use real-world occupancy data from your CBSD (and others). This measured information helps refine our protection calculations, allowing us to move beyond purely model-based worst-case assumptions and produce more accurate power limits where real data is available.

Multi-Stage Protection Evaluation
We evaluate your request against multiple categories of protection requirements that apply in the CBRS band. These include:

Exclusion zones and coordination zones around protected facilities and sensitive operations.
Dynamic Protection Areas (DPAs) whose status can change based on incumbent activity.
Protection of Fixed Satellite Service (FSS) earth stations and other receivers that require careful power management.
Quiet zones and protection areas around FCC facilities.
PAL Protection Areas, ensuring that holders of PAL rights receive appropriate priority.
Cross-border coordination limits, such as power flux density restrictions toward Canada.

These evaluations are performed in two conceptual stages:

Early filtering — Clearly unusable frequencies are removed as early as possible so that later stages focus only on viable candidates.
Power refinement and annotation — For the remaining candidate channels, we calculate the final permissible EIRP after applying every applicable back-off. We also attach high-level explanatory information about any constraints that are active on a channel.

Because each stage builds on the results of the previous ones, the final list of channels you receive represents the complete intersection of all protections known to the SAS at the time of your inquiry.

The outcome is a focused, regulation-compliant response that already incorporates the most current protection data available.

What You Receive in the Response

A successful Spectrum Inquiry response contains an ordered list of available channels. For each channel, we provide the information you need to make an intelligent operating decision:

Frequency range — Always expressed as a standard 10 MHz CBRS channel.
Channel type — PAL (Priority Access License) if the channel falls inside an area where you hold PAL rights, or GAA (General Authorized Access) otherwise.
Maximum permissible EIRP — The highest transmit power (in dBm per 10 MHz) you may legally request after every protection requirement has been applied. This value respects both regulatory limits and your CBSD’s installation capabilities.
Status and constraint information — Clear indicators showing whether the channel is fully available, has a reduced power limit due to one or more protections, or is blocked and should not be used. When constraints apply, we include high-level reason categories so you understand the nature of the limitation (for example, proximity to a protected zone, DPA activity, or aggregate power sharing requirements).

Channels that cannot be used safely are either omitted from the list or explicitly marked as blocked with explanatory reasons. This design allows your system to make a single-pass decision without additional external lookups.

Measurement reports included in your request are processed and queued even if other aspects of the inquiry encounter an issue, helping improve future responses for the entire CBRS ecosystem.

Best Practices for Consuming and Acting on the Response

We recommend implementing a simple, deterministic decision process inside your CBSD or network management system. The response we return contains everything needed to select the best available channel(s) efficiently.

flowchart TD Start[Receive Spectrum Inquiry Response] --> Filter[Filter out blocked channels] Filter --> PAL{ any PAL channels available? } PAL -->|Yes| PreferPAL[Prioritize PAL channels] PAL -->|No| Highest[Select channel with highest max EIRP] PreferPAL --> Highest Highest --> Constraints[Review constraint reasons for diagnostics & planning] Constraints --> Fallback{All channels blocked or power too low?} Fallback -->|Yes| Options[Re-query with narrower list or relocate antenna] Fallback -->|No| Use[Use selected channel in Grant Request] Options --> Use style Filter fill:#ffe6e6,stroke:#cc0000 style Use fill:#e6ffe6,stroke:#009933

1. Discard Unusable Channels Immediately
Filter out any channel that is marked as blocked or unavailable. These channels have failed one or more protection checks and are guaranteed to result in a denied Grant request. Attempting to use them wastes time and resources.

2. Prioritize PAL Channels When Available
If you hold PAL rights and any of the returned channels fall inside your PAL Protection Area, give those channels strong preference. PAL channels provide priority access and are generally subject to fewer coordination restrictions than pure GAA channels.

3. Select the Highest-Power Usable Channels
Among the channels that remain after filtering, choose the one(s) offering the highest maximum EIRP. Because our system has already applied every required protection back-off, this value represents the highest legal power you may request on that channel.

4. Use Constraint Information for Diagnostics and Planning
When several channels offer comparable power, prefer those with no active constraints or only minimal ones. Channels carrying active constraints (even if still usable) may be more sensitive to future changes in aggregate usage. The reason categories we provide also help you understand your local RF environment, plan antenna placement, and decide whether a follow-up inquiry with a different frequency list or location would be beneficial.

5. Apply a Clear Fallback Strategy
If every channel returned is either blocked or reduced below the minimum power your deployment requires, consider the following options:

Re-issue the Spectrum Inquiry with a narrower or shifted frequency list to avoid problematic bands.
If your CBSD or antenna is relocatable, make a small positional adjustment and query again.
Reach out to Key Bridge Wireless support. Persistent restrictive responses may indicate opportunities to improve results through additional measurement data or configuration review.

We strongly recommend coding the above logic as a single, repeatable pass in your device or management software. The response is intentionally designed to be directly actionable.

Why Our Approach Benefits Your Deployment

By performing a comprehensive, multi-stage protection analysis on your behalf, Key Bridge Wireless delivers several practical advantages:

You receive channels that are already safe and fully compliant with Part 96 — no need to second-guess regulatory requirements.
Power limits are realistic and, where available, informed by actual measurement data rather than worst-case models alone.
The response provides actionable metadata (channel type, precise power limits, and constraint reasons) that supports automated, high-success-rate decision making.
Early removal of impossible channels and fair-share power calculations help maximize overall spectrum efficiency while protecting incumbent users.
The process is fast, deterministic, and repeatable, supporting reliable large-scale CBRS deployments.

Summary

Our Spectrum Inquiry service conducts a thorough, sequential evaluation that applies every relevant protection rule before returning any channels. The response you receive is deliberately rich yet easy to consume: discard blocked channels, prefer PAL where you have rights, select the highest-power options, and consult the constraint information for diagnostics and future planning.

Following the straightforward best practices outlined in this guide will help you achieve the best possible grant success rate while remaining fully compliant and good neighbors in the shared CBRS spectrum environment.

For questions about specific responses, integration assistance, or feedback on this guidance, please contact Key Bridge Wireless support.

Questions? Contact us

© 2026 Key Bridge Wireless LLC. All rights reserved.
This document is provided for informational purposes to assist CBSD operators in understanding and effectively using our Spectrum Inquiry service.

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Spectrum Inquiry SIQ Guide