How CBRS is shared

A database decides which radio may transmit

Part 96 of the FCC’s rules splits 3550 to 3700 MHz among three tiers of user. What makes the band unusual is that no radio may transmit until a Spectrum Access System, a database run by a private company the FCC has certified, has given it a channel and a power level (Exhibit 1).

Federal users come first: every other radio “must not cause harmful interference to and must accept interference from” them (§ 96.15). Below the federal tier come the Priority Access Licences, which the FCC sells at auction. Each one is a single 10 MHz channel in the lower 100 MHz of the band, in a single county. Below those again is General Authorized Access, which anyone with certified equipment may use without a licence. A GAA radio may take any channel the database finds idle, including a PAL channel its holder has not built, and in return it gets no protection from the other GAA radios around it.

The top 50 MHz is kept for GAA, and no county may carry more than seven PALs, so GAA is never left with less than 80 MHz. The Commission said as much in 2015 and again in 2018. Both licensed tiers share one set of power limits. A Category A radio may transmit 30 dBm per 10 MHz, which is a watt; a Category B radio 47 dBm, which is about 50 W; and an end-user device 23 dBm. When a federal signal is detected, the database has 300 seconds to move or silence every radio nearby (§ 96.15(a)(4)).

One of the six databases is far larger than the rest

The FCC certifies the companies that run a Spectrum Access System for five years at a time. Eight have been certified since the band opened; in March 2026 the Wireless Bureau wrote that “six of the SASs still operate today” (DA 26-280). One of the six is leaving. Google, among the first four certified, stopped taking customers on 10 June 2026 and closes its database on 10 June 2027 (Exhibit 2).

Three points follow from the table.

• Share. Federated’s share of the band is large and unmeasured. The company said over 75% in September 2025, Fierce put it at about 83% in June 2026, and its chief executive told SDxCentral about 45%. No figure from outside the databases narrows that range.
• Migration. Every customer Google has must move, to Federated or to one of the other four operating databases, before 10 June 2027.
• Certification. The FCC renewed CommScope’s certificate after the company had stopped selling the service. A certificate shows that a company may run a database; it says nothing about whether it does.

No rule has followed the 2024 letter that loosened federal protection

Federal protection is calculated, and the inputs to the calculation decide how many radios around a protected site must be turned down. On 11 June 2024 NTIA wrote to the FCC and changed two of them. The databases may now assume that a radio transmits 80% of the time at 20% loading, which takes 8 dB off the power used in the interference calculation, and they may count the loss from clutter for any radio mounted at or below 6 metres. The FCC authorised five databases, Federated, Google, Key Bridge, RED and Sony, to use the new model on 3 July 2024 (DA 24-643). NTIA estimated that the databases could serve about 72 million more people, some 240 million in all, “without periodic service adjustments”.

The industry reported a large effect within six months. In December 2024 the OnGo Alliance said that interruptions caused by Defense activity had fallen by 85%, and that an indoor radio below 6 metres was now exempt from pre-emption across 97% of the country. The sensor networks still have to work. Between 23 January and 25 September 2026 the Bureau granted Federated seven emergency waivers of its sensor rules, one each time a storm approached (Exhibit 3). The first was for Winter Storm Fern on the East Coast and the seventh for Tropical Storm Nolo in Hawaii.

The changes that cut interruptions for most users of the band rest on a letter from NTIA and two Bureau notices. The rulemaking that would write them into Part 96, FCC 24-86 of August 2024, has produced no order in more than two years. We would expect a user to want that settled before investing; part 4 sets out what else the same notice holds open.

Mobile and cable operators paid 86% of what the county licences cost

The FCC sold the Priority Access Licences in Auction 105, which ran from 23 July to 25 August 2020. The closing notice of 2 September lists every bidder with what it won and what it paid.

Of 271 qualified bidders, 228 won something. Between them they took 20,625 of the 22,631 licences on offer, which is 91.1%, for $4,585,663,345 in gross bids and $4,543,232,339 after bidding credits. The licences were seven in each of 3,233 county areas. Per unit of spectrum and population the price was low. A PAL cost $0.198 per MHz-POP per licence, against $0.852 for the C-band and $0.662 for 3.45 GHz, less than a quarter of the C-band price (direct-to-device part 4). The spectrum cost tool breaks it down county by county.

Filed FCC DA 20-1009, 2 Sep 2020, and Attachment A; FCC Auction 105 page

Five companies paid 86.0% of the gross between them, and they bought for different reasons (Exhibit 4). Verizon took 557 licences in 157 counties at about $3.4 million each, adding capacity where its traffic already is. DISH, bidding as Wetterhorn Wireless, took 5,492 licences in 3,128 counties at about $166,000 each to buy a national footprint cheaply. The three cable companies, Charter, Comcast and Cox, paid $1.14 billion between them, 24.8% of the total. Charter’s 10-K says it will run its 210 licences alongside GAA spectrum on small cells, for a data-only mobile network of its own.

Mobile and cable operators decided the PAL market. Verizon, DISH, Charter, Comcast and Cox paid 86.0% of the gross. The twenty utilities, energy producers, education bodies and Deere, the buyers the band is usually said to be for, paid 4.0%.

Most of the band’s licences come up for renewal on one day in March 2031

A PAL runs for ten years, and at the end of the term its holder must show substantial service or lose it. Because nearly all of the licences were issued on the same day, nearly all of them reach that test together.

The Wireless Bureau issued 17,450 licences on 12 March 2021 (DA 21-300) and 2,725 more in five notices running to October 2022, a total of 20,175. That leaves 450 of the 20,625 sold that were never issued. Some belong to bidders who missed payment deadlines and had their applications dismissed, among them the 122 won by LocaLoop and the 42 won by Hilliary Acquisition. Others Cable One gave up to stay within the cap of four licences per county.

The FCC’s licence file of 4 October 2026 holds 20,185 active PALs. Of those, 17,460, or 86.5%, expire on 12 March 2031: 17,448 of the licences issued that day in 2021 and 12 issued since on the same term (Exhibit 5). A second, smaller cohort of 2,431, issued on 26 July 2022, runs to 26 July 2032. The largest holder carries the date in its accounts. EchoStar’s FY2025 10-K records its PALs at $912.2 million with a final build-out date of “March 12, 2031”.

Three rules meet on that day.

• Renewal. Under § 1.949 a holder may apply no sooner than 90 days before expiry, so the window opens on 12 December 2030. It must show that the licence has been used to serve the public or to carry the holder’s own communications.
• Build-out. Under § 96.25(b)(4) a holder must provide substantial service by the end of the term or forfeit the licence “without further Commission action”. No decision is needed; the licence lapses on its own.
• Evidence. The safe harbour for a mobile service is coverage of half the county’s population, and the only evidence the FCC will look at is radios registered with a database. A licence with no registered radios has nothing to show.

The file shows 304 distinct active holders. EchoStar’s Wetterhorn has 5,491 licences, 27.2% of the total. SAL Spectrum holds 1,424, AMG Technology Investment Group 1,068, and Uniti Services the 1,014 that Windstream won. Comcast has 830, NE Colorado Cellular 558 and Verizon 557. AT&T holds none and T-Mobile two.

Of the 20,185 PALs still active, 17,460 (86.5%) expire on 12 March 2031. Their build-out showing falls on the same day, and the FCC accepts only radios registered with a Spectrum Access System as evidence. A licence bought in 2020 and left unbuilt has a little over four years to be built, leased or sold.

Most of the radios are outdoors and on the open tier

The only count of the band’s radios with a stated definition is NTIA’s, built from the databases’ own records and ending on 1 July 2024 (Exhibit 6).

The last column of the table shows what the band is mainly used for. Nineteen radios in twenty are the higher-power class. Two in three are in rural census blocks, seven in ten hold only GAA grants, and more than half run an air interface that is neither LTE nor 5G NR. That profile is outdoor fixed wireless, with carrier capacity layered on top. CTIA, the carriers’ association, read the report the same way in December 2024.

Growth has slowed. The databases added 95,692 radios in 2022, 78,058 in 2023 and 35,312 in the first half of 2024, a pace a little below 2023 and well below 2022. Later totals of 422,000 to 450,000, published by advocates in 2026, use definitions of their own and cannot be set beside NTIA’s.

Indoor radios were 17,795 of 400,403 on the last neutral count, or 4.4%. The in-building enterprise use the band is so often described by is its smallest part; part 2 and part 3 take it up. One caution applies to every figure in this section: a radio count measures devices and says nothing about networks, users or traffic.

Terms used

• SAS, Spectrum Access System. A database run by an FCC-certified company that registers every radio in the band and grants it a channel and a power level.
• ESC, Environmental Sensing Capability. A network of sensors that detects federal radar and tells the SAS to move or silence radios nearby.
• DPA, Dynamic Protection Area. A pre-defined area offshore or around a federal site, activated when federal radar is present. Radios nearby may be moved, turned down or switched off.
• CBSD, Citizens Broadband Radio Service Device. A base station or fixed customer radio registered with a SAS, in a low-power Category A or a higher-power Category B. Phones are not CBSDs.
• PAL Protection Area. The area around a PAL holder’s registered radios, bounded by a −96 dBm/10 MHz contour by default, inside which GAA users must not interfere with it.