CBRS is 150 MHz of spectrum – ranging from 3550 – 3700 MHz – in the 3.5 GHz band. Used by the U.S government and other entities. In April 2015, the FCC established Citizen Broadband Radio Service (CBRS) for shared commercial use of that band. Some of this spectrum will continue to be used by the United States government for radar systems, but will be available for others where not needed by the Navy. When operating in shared spectrum, users with different levels of priority have access to the band, there are 3 tiers of users in CBRS: – Tier 1 (higher priority): Naval aircraft carriers, Fixed Satellite Stations, GWBL/GWPZ – Tier 2: Priority Access Licensee (PAL) – Tier 3: General Authorized Access (GAA)
Higher priority users must be protected from interference by lower-priority users.
A system that authorizes and manages use of spectrum for the Citizens Broadband Radio Service. SAS determines the available frequencies at a given geographic location for CBSDs and communicate that information to the SAS manager. 1- Determine the maximum transmission power level for CBSDs at a given location and communicate that information to the SAS manager. 2- Register and authenticate the identification information and location of CBSDs. 3- Ensure secure and reliable transmission of information between the SAS and Domain-Proxy
3.5 GHz CBRS band is dubbed the Innovation Band by the FCC due to the unique sharing concept used in CBRS and can be applied to many other bands in the future. The main difference between CBRS and current other bands is the application of three tiers of spectrum-use rights, which are managed by the SAS and ESC. This band also provides up to 150 MHz for use by several different types of applications through a hybrid licensing scheme that allows a mix of licensed and lightly licensed operation.
CBSD – Citizens Broadband Radio Service Device: Fixed Stations, or networks of such stations, that operate on a Priority Access or General Authorized Access basis in the Citizens Broadband Radio Service consistent with this rule part.
Telrad’s solution, CBSDs are eNBs and UEs. A CBDS shall operate at or below the maximum power level and frequencies as authorized by the SAS.
A CBSD shall be registered by SAS to be able to make requests for Spectrum Grants (service transmission). As part of the CBSD Registration procedure, Domain-Proxy provides the SAS with its device specific information, like device type, serial no, FCC ID, etc. as well as its installation information like location, height, deployment type, etc. The SAS validates the CBSD authenticity and registration information to verify the correctness of the data provided by the Domain-Proxy and whether the CBSD is blacklisted and has to be denied service.
CBSD Grant The Grant procedure is used for a Registered CBSD to request access for the spectrum managed by the SAS. This procedure can only be performed after a successful registration of the CBSD with the SAS. The Grant Request should include: 1- The CBSD frequency range it wishes to operate upon. 2- The desired maximum TX power. On successful operation, SAS sends a successful Grant Response with information on the duration of the Grant validity and allowed peak transmit power, an the Heartbeat Duration.
CBSD Heartbeat The Heartbeat procedure is used to maintain the validity of the CBSD assigned Grants with the SAS. Heartbeat request informs SAS that the CBSD still using the allocated spectrum, and allows SAS to suspend or terminate the grant. The SAS uses the HB Response message to inform a state change, such: – Grant Expiry time – Transmit Time – Grant Status: Termination or Suspension.
CBSD Deregister Deregistration Procedure is used by the BreezeVIEW to deregister a CBSD from the SAS.
CBSD Relinquish The Spectrum Relinquishment procedure used by the Domain-Proxy to relinquish an assigned/active Grant for a CBSD. The Domain-Proxy sends the Relinquishment Request message to the SAS to inform the SAS that the CBSD no longer requires use of the frequency segment assigned in the Grant. BreezeVIEW Domain-Proxy may initiate this request for the following state transitions: 1- CBSD is no longer reachable/managed. 2- CBSD is no longer going to transmit on the frequency segment assigned in the Grant. 3- SAS has instructed to vacate the frequency segment assigned in the Grant. 4- Switching CBSD to a different operating frequency
To learn which spectrum is available at its location, a registered CBSD can send a spectrum inquiry request to the SAS.
The SAS will respond with:
Detailed information about which frequencies are available for the CBSD to use.
Additional information which might be useful to the CBSD when it’s selecting a frequency range to transmit on.
Note: The word “channel” is frequently used to describe a 10 MHz segment of the CBRS band.
A channel is marked as unavailable to the CBSD if the SAS
is unable to authorize any transmissions on that channel at the CBSD’s
location. For example, the SAS is not allowed to authorize transmissions
inside of exclusion zones. Otherwise, the SAS indicates that the
channel is available for use.
Note: In order to meet operational
security requirements from the DoD, Google’s SAS does not indicate which
channels are currently affected by Naval operations.
If the spectrum inquiry request was malformed, the SAS will
reject the request. Examples of malformed requests include having an
invalid frequency range or an invalid CBSD ID.
Most high-priority users operate
continuously at a well-known location. However, Naval radar operations
can happen at different places and different times.
In order to maximize the amount of spectrum available for commercial use, the SAS
uses specialized sensors (ESCs) to detect when and where the Navy is
using the band. When they use the band, the SAS must adjust the
operation of the CBSDs under its control to ensure that they do not
disrupt the Navy’s operations.
In particular, when the SAS learns that incumbent activity
has been detected in a Dynamic Protected Area (DPA), it activates
protections for that DPA. When a DPA is activated, all grants that cause
too much interference to Navy operations are suspended.
The SAS uses a DPA move list to keep track of which grants
must be suspended during incumbent activity. As the following table
shows, the grant only needs to be suspended if it’s on the move list and
incumbent activity is detected.
Grant is on the move list
Grant is not on the move list
DPA is active
DPA is not active
When a grant is added to a move list
Each night the SAS recalculates which grants must be suspended during incumbent activity and updates its DPA move lists.
It does this by ranking all grants on the corresponding
channel according to the interference they would cause to the DPA. It
removes as many low-interference grants as possible from the move list,
but must add the remaining higher-interference grants to the move list.
This means that a grant’s membership on the move list is determined both
by its own characteristics and by the characteristics of other nearby
During the day, all new grants which may impact the DPA
must be added to the move list. A grant is considered to potentially
impact a DPA if it is in that DPA’s neighborhood. As a general rule of
thumb, neighborhoods have the following approximate sizes:
FCC Part 96 rules require that applicable CBRS Devices (CBSDs) be professionally installed. A Certified Professional Installer (CPI) may physically install the CBSD her/himself or may take the responsibility for accuracy of the data entered into the CBSD by another installer. All Category B CBSDs require CPI.
SAS Vendors provide access to their Web Portal (GUI) instance, the operator should use it for CBSDs provisioning.
Certified Professional Installers (CPI) uses their digital credentials to sign installation parameters for all CBSDs devices (mandatory for Category B CBSD registrations).
You should get the following information from the SAS vendor:
CPI digital certificate (usually file extension p12 or private certificate)
Serves as SAS managing intermediary such that the SAS communicates directly with the Domain-Proxy rather than with each individual CBSD. BreezeVIEW acts as a Domain-Proxy and supports the following main functions: 1- Accept a set of one or more available channels and select channels for use by specific CBSDs, and configure the CBSDs respectively. 2- Receive confirmation of channel assignment from SAS, manage CBSDs registration and authorization with the SAS 3- Perform bidirectional bulk CBSD registration and directive processing.
Telrad’s NMS: BreezeVIEW supports the Domain Proxy capabilities.
BreezeVIEW acts as a Domain-Proxy between SAS and the Devices (eNBs, UEs). It communicates with the SAS, accepts instructions such a grant confirmation or denial for requested spectrum, and configure the CBSDs (eNBs, UEs) respectively.
The Domain-Proxy maintains a state machine algorithm per CBSD, and provides information about the CBSD state and statuses. CBSD state may be affected by variant causes, such SAS instructions, CBSD HW state, connectivity’s state and others.
The Domain-Proxy automatically configures eNB and UE devices following SAS instructions, user configuration, and the state machine algorithm. For example, when receiving a Grant for eNB CBSD, SAS manager shall configure the Central Frequency, Max TX power and activate Start Transmission operation, or alternatively, stops eNB transmission if Grant is rejected.
By definition, PAL is licensed and is afforded interference protection from GAA. PAL licenses will be purchased at auction. There will be up to 70 MHz of PAL spectrum available in any area, which can be chosen from 100 MHz of the CBRS band (3550–3650 MHz).
Many refer to GAA tier users as unlicensed users. However, although GAA users do not require a license, they must meet the FCC’s technical, financial, character, and citizenship qualifications to be eligible as a GAA user. Use cases may differ slightly between PAL and GAA.
The FCC plans to hold the auction of Priority Access Licenses in the 3.5 GHz Citizens Broadband Radio Service on June 25, 2020. Until the PAL channels are auctioned off, full 150 MHz of the band can be used as GAA.
The Environmental Sensing Capability (ESC) is a network of sensors used to detect federal frequency use in the 3550–3650 MHz band in protection zones where U.S. Navy radar systems can operate, primarily along the Pacific, Atlantic, and Gulf coasts. The ESC informs the SAS of radar operation and the SAS reacts to ensure there is no interference between CBRS and radar operations.
CBRS and cell lock are compatible between them. If BV detect that CPE is working in a channel that was not the granted, it cancel the current grant and ask the grant for the channel that the CPE is using.
This is dynamically performed by BV, to adapt and allow the CPE to move. However please note that each Grant request can be Granted by SAS indemnity, after a maximum of 24 hours or never.
CPE 9000 : Unlock Specific Cell Time, My general advice is good to configure (example 20 minutes) because it work as catch all mechanism. However it was a bug (which is in the process to be fixed), so please leave for later or check carefully.
ENBs will stop transmission after 4 to 5 minutes because CBRS standard has TransmitExpireTime with a value of 4 minutes. BreezeView will raise alarms, the System will recovery automatically after connectivity between BreezeView and SAS was recover.