CBSD Bootstrapping Procedure

Bringing a CBSD Online with Key Bridge SAS

Document Purpose

This document describes the complete bootstrapping process a Citizens Broadband Radio Service Device (CBSD) follows to become operational with the Key Bridge Spectrum Access System (SAS). It covers both the critical pre-SAS authorization step and the subsequent protocol interactions required by the WinnForum SAS Functional Requirements and FCC Part 96.

The goal is to provide CBSD operators and integrators with a clear, end-to-end understanding of how a device transitions from an unauthenticated radio to a fully authorized, transmitting CBSD.

Sequence Overview

Step-by-Step

Step 0: Device Authorization (Pre-Registration)

Before a CBSD can successfully register with the Key Bridge SAS, it must first be authorized to operate under a customer account. This step occurs outside the SAS protocol and is a mandatory prerequisite.

Authorization Requirements

• Every device must be associated with a valid Key Bridge customer account.
• Authorization is typically performed through the Key Bridge CBRS Portal.
• Authorization is realized by linking the device’s fccId and serialNumber to the customer’s account.

Category A Devices

• Default Path (Recommended):
  The fccId, serialNumber, and complete installation configuration are pre-registered in the Key Bridge system via the portal. This is the most common and reliable method.

• Alternate Path (Rare):
  Only the fccId and serialNumber are pre-registered. The device must then include a complete installation information package in its SAS registration request.

Category B Devices

• Default Path (Recommended):
  The fccId, serialNumber, and a CPI-signed installation configuration are pre-registered through the Key Bridge CBRS Portal.

• Alternate Path (Rare):
  The device is authorized with Key Bridge using only its fccId and serialNumber. A cryptographically signed device installation configuration is then included with the registration request sent to the SAS.

Device Installation Configuration

A Device Installation Configuration contains the information required to authorize and locate the device. It includes:

• fccId and serialNumber (used for authorization matching)
• Geographic position (latitude and longitude)
• Antenna configuration details, including:
  • Height above ground level (AGL)
  • Antenna beamwidth
  • Antenna gain
  • Antenna pointing angle / azimuth
  • Additional installation parameters as required by the device category

Step 1: CBSD Registration with the SAS

Once device authorization (Step 0) is complete, the CBSD may contact the Key Bridge SAS.

Purpose
Registration establishes the device’s identity and operational parameters within the SAS. Upon successful registration, the device receives a cbsdId and transitions to the REGISTERED state.

Key Requirements

• The device must have completed Step 0 (authorization).
• The registration request must contain valid fccId, serialNumber, and installation parameters consistent with the pre-authorized configuration.
• Category B devices must include valid CPI-signed data (unless using the rare alternate path).

Outcome
A CbsdData record is created in the Key Bridge system. The device is now known to the SAS and may proceed to spectrum discovery and grant requests. Any previously existing grants for the device under the same administrator are terminated upon re-registration.

Step 2: Spectrum Inquiry

After successful registration, the CBSD may perform a Spectrum Inquiry to discover available spectrum resources.

Purpose
Spectrum Inquiry allows the CBSD to learn which 10 MHz channels are potentially available at its location before requesting a grant.

Key Characteristics

• The device must be in the REGISTERED state.
• Spectrum Inquiry is optional but recommended before requesting a grant.
• The SAS returns a list of available channels based on current protection and coordination requirements.
• Measurement reports may be included or requested depending on device configuration.

Step 3: Grant Request

The CBSD requests a spectrum grant to obtain transmission rights.

Purpose
A grant provides the CBSD with authorized frequency range(s), maximum EIRP, and an expiration time. Grants are the fundamental unit of spectrum authorization in CBRS.

Key Characteristics

• The device must be registered.
• The requested frequencies should typically come from a prior Spectrum Inquiry.
• The SAS evaluates the request against regulatory constraints, DPA move lists, PAL protection areas, and other incumbent protections.
• A grant may be issued in GRANTED state or immediately placed in SUSPENDED state (commonly due to active DPA constraints).

Outcome
Upon success, the SAS returns a grantId. The grant is now tracked by the SAS and must be actively maintained by the CBSD.

Step 4: Heartbeat (Grant Maintenance)

Once a grant is acquired, the CBSD must repeatedly send Heartbeat messages to keep the grant active.

Purpose
Heartbeat serves as the keep-alive mechanism for grants. It allows the SAS to confirm the CBSD is still operating and to manage grant state transitions (including suspension and unsuspension).

Key Requirements

• Heartbeat is grant-specific — each active grant requires its own Heartbeat sequence.
• The CBSD must send Heartbeats at the interval specified by the SAS (with jitter).
• Heartbeat is used to:
  • Prevent grant expiration and TIMED_OUT termination
  • Extend grant time-to-live (via grantRenew or autoRenew)
  • Respond to state changes (e.g., DPA-related suspension)
  • Deliver required measurement reports when enforced

Operational Note
A grant will eventually terminate if the CBSD stops sending Heartbeats. The CBSD Agency is solely responsible for maintaining continuous Heartbeat operation for every active grant.

Installation Configuration Details

The installation configuration is central to both authorization and ongoing operation:

• It binds the physical device (fccId + serialNumber) to a specific location and antenna setup.
• Category A devices generally use simpler installation data.
• Category B devices require CPI-signed installation data in the default flow to satisfy higher-power regulatory requirements.
• Any change to location or antenna configuration after initial authorization typically requires re-authorization through the Key Bridge portal and may necessitate re-registration.

Category A vs. Category B Operational Differences

Summary: CBSD Online Lifecycle

A CBSD becomes fully operational through the following sequence:

1. Step 0 — Device is authorized and linked to a customer account via the Key Bridge CBRS Portal (pre-SAS).
2. Step 1 — CBSD successfully registers with the SAS and receives a cbsdId.
3. Step 2 — CBSD performs Spectrum Inquiry to discover available channels (recommended).
4. Step 3 — CBSD requests and receives a spectrum grant (grantId).
5. Step 4 — CBSD begins sending regular, grant-specific Heartbeats to maintain the grant and remain operational.

The CBSD Agency is the prime actor responsible for driving every step in this lifecycle. Successful long-term operation depends on proper pre-authorization (Step 0) and continuous, correct Heartbeat behavior after a grant is acquired.

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