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. This is spectrum traditionally used by the military and commercial satellite and ISP operators. That means, in order to utilize the band, your network must employ a Spectrum Access System (SAS) and have access to an Environmental Sensing Capability (ESC) network to dynamically manage that spectrum use.


2. What is the SAS?

With a Spectrum Access System (SAS), spectrum is managed and assigned on a dynamic, as-needed basis across three tiers of access:

  • Tier 1 is incumbent users such as the federal government and fixed satellite users.
  • Tier 2 is Priority Access License (PAL) users—licensed wireless users who acquire spectrum through an auction. PAL users must protect incumbent Tier 1 users from harmful interference.
  • Tier 3 is General Authorized Access (GAA) users who will deploy “lightly-licensed” devices. GAA users must protect both Tier 1 incumbents and Tier 2 PAL users from harmful interference.

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 market, which can be chosen from 100 MHz of the CBRS band (3550–3650 MHz). Many refer to GAA as unlicensed considering GAA users are not protected for interference from either PAL licensees or other GAA 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.


4. What is the ESC?

The Environmental Sensing Capability (ESC) is used to detect federal frequency use in the 3550–3650 MHz band in exclusion 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?

The main difference 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. When will SASs and ESCs be certified?

Both SASs and ESCs will be certified once they’ve passed the FCC’s Test and Certification program. This program is currently under development in cooperation with the FCC, SAS administrators, the Wireless Innovation Forum (WInnForum) and others. CommScope is one of only a few companies to have been granted conditional approval for our ESC by the FCC. We are targeting 3Q-4Q this year for SAS certification.


7. When will CBSDs be certified?

Communication Broadband Service Devices (CBSDs) should be certified around the same time frame as SAS and ESC: 3Q-4Q this year.


8. When can CBSDs be deployed?

CBSDs can be deployed as GAA once an SAS, ESC and CBSD are certified. This should occur toward the end of 2018. CBSDs can be deployed in PAL once the PAL licenses are auctioned. This should occur in 2019.


9. 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 would allow for increased capacity where needed the most.
  • 5G fixed wireless access (FWA): FWA at 3.5 GHz could deliver peak rates that few technologies could match without deep fixed fiber.
  • Enterprise neutral host: With traffic increasingly concentrating indoors, small cells offer a potential solution to issues associated with legacy technologies (DAS, Wi-Fi).
  • Private 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.


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

SAS may not be used per se in other bands, but elements of SAS such as the database and spectrum availability determination could be used in any band where new entrants need to share spectrum with incumbents.


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