FCC Changes to the 3.65 GHz band - CBRS FAQ

Statement and Frequently Asked Questions on the FCC’s New Rules for Commercial Use of the 3550-3700 MHz Band

Cambium Networks has been digesting the Federal Communications Commission’s recent rule changes affecting the 3550-3700 MHz band, as described in the FCC’s recent Report and Order and Further Notice of Proposed Rulemaking (FCC 15-47, released April 21, 2015).  While many changes are coming (and some details remain uncertain), we at Cambium believe that as a whole these changes will benefit not only general use of the band, but will effectively help Cambium Networks customers that are already using the 3.65 GHz spectrum.

The bulk of the new rules will take effect 30 days after FCC 15-47 is published in the Federal Register. In very brief terms, here are key expected changes to the band:

  1. The 3550-3700 MHz (3.5 GHz) band will be licensed as the Citizens Broadband Radio Service (CBRS) under a new Part 96 of the FCC’s rules, effectively expanding (by 100 MHz) the spectrum available in this band for commercial terrestrial wireless operations.
  2. The entire 150 MHz will be managed by a Spectrum Access System (SAS), a database system (or a “highly automated frequency coordinator”) that will determine access availability and priority to limit interference. Equipment approved for use under these rules must operate with the SAS, so that means commercial terrestrial wireless operations at 3550-3650 MHz will not permitted until one or more SAS are in place.
  3. In general, the band will have three tiers of users. This table briefly describes each tier and its relative priority to other users in the band.

3550 – 3650 MHz

3650- 3700 MHz

Protected Incumbent Users (federal and Fixed Satellite Service (FSS))

Priority Access License (PAL) holders

Grandfathered Incumbent terrestrial wireless operations, for a limited transition period

General Authorized Access (GAA) users

4.  Protected Incumbent Users. The FCC’s rules adopted a two-phase approach to protecting Federal incumbent operations such as radar.

a. In the first phase, a large portion of the country will be available for CBRS use once the SAS is approved and made available for commercial use. During this phase, the FCC has established “exclusion zones” (typically coastal regions) where CBRS operations will not permitted, but these zones are about 77% smaller than the zones initially recommended by the National Telecommunications and Information Administration in 2010.

b. During the second phase, the zones will be converted to protection zones, and CBRS operations will be permitted within these zones except when a new system -- environmental sensing capability, or ESC – reports the presence of federal incumbents.

c. Separately, the FCC has adopted protection criteria that apply to a limited number of FSS stations and has sought public comment on additional protection criteria.

5. Priority Access License (PALs) holders are entitled to protection from GAA users

a. PALs will be auctioned only in areas (by census tract) where parties file “mutually exclusive” applications for PALs.

b. PALs are three-year, nonrenewable licenses, but PAL licensees may reapply for subsequent authorizations in limited circumstances.

c. Each PAL is for 10 MHz-wide channels.

d. Up to 70 MHz of the 3550-3650 MHz may be auctioned in a single census tract, but licensees may hold no more than four PALs in one census tract at any time.

e. No PALs will be issued at 3650-3700 MHz.

6. General Authorized Access (“GAA”) use is allowed on a shared basis, by rule, throughout the 150 MHz band, subject to requirements to protect higher-priority users like protected incumbents and PAL licensees. GAA users may use frequencies assigned to PALs when such frequencies are not in use, as determined by the SAS.

7. Grandfathered Wireless Broadband Licensees. As a Cambium customer, if you already have a 3650-3700 MHz license issued under the FCC’s existing Part 90, subpart Z rules, you will be afforded limited interference protection in certain circumstances. For any fixed and base station that you registered with the license in the FCC’s Universal Licensing System on or before April 17, 2015, so long as those registrations are constructed, in service and fully compliant with the FCC’s Part 90 subpart Z rules by April 17, 2016, they will be afforded protection from CBRS transmissions (a “Grandfathered Wireless Protection Zone”). The protection will be based on criteria that the FCC will adopt after seeking public comment, and the operator will be required to register their frequency usage with approved SAS administrators. Depending on the circumstances, this protection will last until the license expires or until April 17, 2020.  Separately, existing licensees as of April 17, 2015 may add new portable or mobile stations and/or add new subscriber units that operate at certain power limits provided that they can positively receive and decode an enabling signal from a base station. Additionally, after April 17, 2015, licensees may register new sites and continue to expand their network and will be afforded protection from harmful interference by CBRS within the licensee’s Grandfathered Wireless Protection Zone for fixed, base, mobile and portable stations. Sites registered outside of these zones will not be entitled to such interference protection. Once the new rules are adopted, commercial terrestrial wireless operations will continue to be allowed provided that they comply with the General Authorized Access (GAA) rules.   

Frequently Asked Questions:

(Last updated on May 20, 2015)

Cambium has prepared and periodically will update the following list of Frequently Asked Questions about the 3550-3700 MHz band. If your question is not addressed below, please post the question in this thread on the foum. 


Q: After adoption of FCC 15-47 (April 17, 2015), can I still apply for a 3650 MHz nationwide license under Part 90, subpart Z?
A: No new 3650 MHz nationwide licenses are expected to be granted under the existing rules.  PALs will be granted under the new rules once the SAS comes online.

Q: Are my existing sites protected?
A: Yes, any sites that you have registered on or prior to April 17, 2015, will be protected under the Grandfathered Wireless Protection Zone, which the FCC will establish around only those base and fixed stations that are registered by applications filed in ULS on or before April 17, 2015 and are constructed, in service, and in full compliance with the rules by April 17, 2016.  This licensee will enjoy interference protection within this zone until the end of the 3650-3700 MHz transition period.  After that, operations can continue under GAA provided that the equipment complies with all applicable rules other than the new requirement for Part 96 devices that the equipment be operable across the entire band. In other words, the Part 90 equipment must, among other things, communicate with the SAS. 

Q: If I already have a license (FCN #), can I register new sites?
A: Yes, you can continue to register new sites, and these location registrations will be reviewed and approved by the FCC.  The requirement is that equipment is deployed, in service and in full compliance with the rules within 1 year of registration approval of a given site.  These newly registered sites do not qualify for Grandfathered Wireless Protection Zone protection.

Q: Can I deploy different equipment at an approved site (i.e. update an approved site registration)? Does this affect my protected status?
A:  The FCC has announced that a separate public notice will be issued to seek public comment on ways to define the technical parameters of Grandfathered Wireless Protection Zones.  Until the FCC sets forth clear criteria, we would expect that the acceptability of site registrations for replacement equipment at a previously approved site would depend on the type of equipment to be registered. In other words, new equipment that is substantially similar to what had previously been deployed would be more likely to preserve the protected status than equipment that effectively would change the protected contour.

Q: If I have equipment deployed already, and the sites are not yet registered, can I still register these sites?
A: Yes. The FCC is continuing to accept registrations.

Q: When will the SAS come online and who will administer this?
A: The FCC intends to issue a Public Notice requesting proposals from entities that seek to administer an SAS, but the exact timing has not been addressed.

Q: How long can we continue to use equipment that is not approved under the new rules?
A: At this time, the FCC hasn’t expressly set a deadline by which Part 90-certified equipment can no longer be sold or marketed.

Q: When will the initial PAL auctions occur?
A: It’s not expected for quite some time. The FCC intends to adopt a supplemental Notice of Proposed Rulemaking to develop the record on changes to the Part I rules to award PALs using competitive bidding. Once the comment cycle is completed and the FCC has made a determination on how to proceed, it would then announce application procedures and a filing window for participation in the PAL auction.