Spectrum Access System (SAS) frequently asked questions

1. What is CBRS?

CBRS is the Citizens Broadband Radio Service that opens up 150 MHz of spectrum in the 3.5 GHz band for commercial use. This is spectrum traditionally used by the military and commercial satellite operators and Wireless Internet Service Providers (WISPs). In order to take advantage of CBRS, your network must employ a Spectrum Access System (SAS) and have access to an Environmental Sensing Capability (ESC) network to dynamically manage the spectrum use.


2. What is the SAS?

The Spectrum Access System (SAS), is an automated frequency coordinator that manages spectrum sharing on a dynamic, as-needed basis across three tiers of access:

  • Tier 1 is incumbent users such as the federal government, fixed satellite users.
  • Tier 2 is Priority Access License (PAL) users—licensed wireless users who acquire spectrum through an auction. The SAS will ensure PAL users do not cause harmful interference to Tier 1 users and will protect PAL users from interference by General Authorized Access (GAA) users.
  • Tier 3 is GAA users who will deploy “lightly-licensed” devices. The SAS will ensure GAA users do not cause harmful interference into Tier 1 incumbents and Tier 2 PAL users.

If spectrum is not being used by one tier it can be accessed by another via the SAS—securely and without harmful interference.


3. How does GAA differ from PAL?

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.


4. What is the ESC?

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.


5. Why is this band different from others?

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.


6. What are some applications for CBRS?

The CBRS band offers a diverse range of deployment options and innovative use cases, including:

  • Small cell networks: Additional network layers based on small cells will allow for increased capacity where needed the most.
  • Fixed Wireless Access (FWA): FWA at 3.5 GHz delivers peak rates that few technologies can match without fixed deep fiber.
  • Neutral Host Networks: With traffic increasingly concentrating indoors, Neutral Host Network operators offer a potential solution to issues associated with legacy technologies (e.g. DAS, Wi-Fi).
  • Private LTE Networks: Local private network utilizing dedicated radio equipment to service a premise with specific applications and services.
  • Massive MIMO Hotspot: mMIMO hotspots would serve the needs of high-usage, high-density areas with relatively low mobility.
  • Industrial IoT: Private LTE or 5G networks on 3.5 GHz could ensure the high reliability and low latency needs for robust IIoT operations.
  • Macro coverage: Emerging 5G RF technologies could enable a 3.5 GHz layer overlaid on the existing macro grid.


7. What are other bands where an SAS might be used?

Elements of SAS such as the database and spectrum availability determination can be applied to other bands. Spectrum sharing is currently being considered for other bands where the incumbents may be difficult to relocate off the band.


8. Do I need to install any hardware or software products in my network to support SAS or ESC?

SAS is a cloud hosted service that does not require any infrastructure to be installed in an operator’s network. Citizens Broadband Radio Service Devices (CBSDs) installed in the operator’s network are programed to connect securely to the SAS via the internet.

There is no direct interaction between the ESC and an operator network. The ESC only interfaces with the SAS.


9. What do I need to implement CBRS in my network?

Here is a high-level checklist of items for deploying a CBRS wireless network:

  1. Make a determination whether for your specific business case you will require a PAL license or whether the GAA use of the band will meet your business needs adequately.
  2. Perform a spectrum availability analysis for your target area of deployment. CommScope can perform a detailed analysis for you and make PAL channel recommendations.
  3. Select a SAS vendor. Some operators select their own SAS vendor independently, while others pick from the SAS options provided by their Radio Access Network (RAN) provider. In almost all cases, a SAS with an ESC network behind it will be needed. CommScope is a leading SAS/ESC administrator and supported by most major RAN vendors.
  4. You will need a CBRS compliant RAN, which is essentially a network of radio devices, e.g. small cells, or Fixed Wireless base stations along with Customer Premises Equipment (CPE). Depending on your RAN equipment provider, you may need to purchase a Domain Proxy separately.
  5. If this is a greenfield LTE network deployment, you will also need:
    1. An Evolved Packed Core (EPC)
    2. If you are not experienced in LTE network installation, an Integrator to install everything for you correctly*
    3. If you are not experienced in LTE network operation and management, a hosting service to manage and monitor your network

CommScope offers turnkey CBRS networks. We also work with several partners in the above expertise areas and can recommend the right one for your network type.

* You or your integrator may need a Certified Professional Installer (CPI) to approve your CBSD installation. More on CPI below.


10. What is a Domain Proxy?

According to WInnForum, a Domain Proxy or DP is, “An entity engaging in communications with the SAS on behalf of multiple individual CBSDs or networks of CBSDs. The Domain Proxy can also provide a translational capability to interface legacy radio equipment in the 3650-3700 MHz band with a SAS to ensure compliance with Part 96 rules.” Keep in mind that the Domain Proxy cost to utilize CBRS on preexisting legacy equipment may be significant in some cases.


11. What is the CPI requirement?

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. Category A CBSDs installed above six meter Height Above Average Terrain (HAAT) and unable to self-geolocate also require CPI.

CommScope is a CPI Training Program Administrator (TPA) for CBRS. The accreditation allows CommScope to offer training to installation professionals who want to attain CBRS CPI certification. More information and pricing for CommScope’s training program is available here.


12. What are the different categories of CBSDs?

There are two CBSD categories as following:

  Maximum EIRP (dBm/10 MHz)
Category A 30
Category B 47


13. Where can I learn more about CBRS?

Watch this 25 minute video to learn more about CBRS, SAS, ESC and the different use cases in detail.

Still have questions? Contact us here.


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