Who pays for coverage nobody owns

The building’s construction sets the loss at every band

Recommendation ITU-R P.2109-2 is the ITU’s model of how much signal a building takes out of a link. It sorts buildings into two populations, which differ by 15 dB or more at every mobile frequency (Exhibit 1).

One population is “traditional” buildings. The other is buildings where “modern, thermally-efficient building methods are used (metallised glass, foil-backed panels)”. At 3.625 GHz, the middle of CBRS, the model’s median loss at horizontal incidence is 15.8 dB for a traditional building and 30.9 dB for a thermally efficient one. Those are medians; a tenth of indoor locations lose more than 28.8 dB and 49.4 dB respectively. The 6G series found the same two populations from 3.5 to 7.125 GHz, so the effect is not peculiar to the CBRS band.

Low band does not help. At 700 MHz the model gives 31.6 dB for a thermally efficient building, worse than at CBRS frequencies, and 14.1 dB for a traditional one, a saving of under 2 dB. The gap between the two classes is widest there, at 17.5 dB.

Fifteen decibels is a factor of about 32 in power, and a carrier cannot buy it back with a different licence. The only way to serve the building is to bring the signal inside, with a system in the building or a small cell close enough to it. Regulators have begun to write walls into their rules: the FCC’s January 2026 proposal on 6 GHz would let the databases that set standard-power Wi-Fi limits count up to 6 dB of building entry loss. How much traffic is at stake is less settled than the usual “80% indoors” suggests. When Ericsson measured one operator’s 4G network in 2021, indoor users accounted for about 64% of the traffic on outdoor cells in an urban district and 37% in a dense high-rise area, a large and variable share.

The gap between the two classes of building is 15 dB or more at every band from 700 MHz to 7 GHz, and low band does not close it. Whether a building can be served from outside is settled by its glazing and its insulation, and no spectrum purchase changes either.

Published costs for the same building differ by up to nearly seven times

The only published figures for what an in-building system costs come from the companies that sell them, and for the same building they differ by a factor of two to nearly seven (Exhibit 2).

Two of the savings claimed against DAS come without a price attached. Celona, via RCR Wireless in April 2025, said its neutral host was “nearly half the cost” of DAS. Meta, via Light Reading in April 2023, said its CBRS office network was “75% faster” to deploy and did not say what it cost. The spread in the published figures has a cause. Wilson’s own price more than doubles between an active system for one carrier and one for several, because each additional carrier is another signal source to supply and another approval to win, which is where cost meets permission.

The owners of infrastructure between carrier and building have sold up or shrunk

For a time a third party paid for coverage nobody owns: a company that built small cells and in-building systems and rented them to carriers. Those companies spent 2025 and 2026 leaving the business or shrinking in it (Exhibit 3).

Crown Castle agreed in March 2025 to sell its small cells to an EQT fund and its fibre business to Zayo, each for an enterprise value of $4.25 billion. The sale closed on 1 May 2026, and the small cells now trade under the name Arium Networks. American Tower is still in the business and shrinking slowly in it. Its count of DAS sites in the United States fell from 434 to 429 between FY2024 and FY2025, and its 10-K mentions neither neutral host nor CBRS. ExteNet Systems, a private small-cell owner, wrote to its banks on 15 June 2026, as Fierce Network reported, and said it expected it “will not have sufficient funds to continue to operate” as early as 25 June. The one company raising money is Boldyn Networks, 86% owned by CPP Investments, which raised $1.2 billion of debt for the United States in February 2025 and reports about 110 private network implementations.

The independent layer between carrier and building has thinned. Crown Castle sold about 105,000 small-cell nodes after about $6.5 billion of write-downs, American Tower’s DAS count in the United States fell by five, and a specialist warned it could run out of cash. Whatever money is left for in-building coverage is the building owner’s.

The owner pays for a system the carrier must approve

Carriers once paid for in-building systems; in most buildings they now approve them instead.

The shift was visible as early as 2017, when the analyst Iain Gillott wrote that “very few DAS projects are funded exclusively by the mobile operators”. By now it is written into the carriers’ own programmes. The 5G Americas white paper Neutral Host Opportunities for 5G and Beyond (July 2024) sets them out; Blue Prysm’s founder, Colin Bowdery, co-led the working group that wrote it while he was at Ericsson. The paper names three enterprise-funded programmes: AT&T Direct, T-Mobile’s Build Your Own Coverage and Verizon’s Coverage Extension Radio Access Network. They “empower enterprises to finance their own NHN deployments and re-utilize licensed spectrum”. The operative word is finance. Medium and low-capacity venues, the paper goes on, “will have to either partially subsidize the system cost or completely fund it themselves”.

The paper also records why the neutral host has stalled. Sharing the whole radio network, carriers’ spectrum included, “has yet to gain widespread approval among MNOs due to perceived security and control limitations”. That approval is the question for a CBRS neutral host, which broadcasts several carriers’ network identities so that their customers’ phones will attach to it and works only for the carriers that have certified it. The three national carriers have taken three different positions, as reported (Exhibit 4).

The standard allows every form of sharing

There are two ways to share a radio network, and the difference is whose spectrum the shared radio uses (Exhibit 5).

TS 23.501, in its Release 19 version of September 2026, lets one radio network be shared by “any combination of PLMNs, PNI-NPNs (with CAG) and SNPNs”: carriers, private networks built on a carrier and stand-alone private networks, in any mix. Three releases added the pieces a neutral host needs.

• Release 17. A credentials holder, so that a carrier’s credentials admit its subscribers to somebody else’s private network.
• Release 18. A hosting network for localised services.
• Release 19. Indirect network sharing, in which a hosting operator runs the core that each participating carrier connects through.

Every neutral-host model under discussion has a standard form already. What is missing is the carriers’ permission, and the base from which a CBRS neutral host would have to grow is small: indoor radios were 4.4% of the band on NTIA’s last count (part 1).

A thermally efficient building costs 15 dB or more, and no carrier pays by default to close that gap. The infrastructure owners have retreated, the building owner pays, and the carrier keeps the veto. On CBRS one national carrier says yes, one prefers its own licensed spectrum, and one decides building by building. Part 5 turns this into a rule.

Terms used

• Building entry loss. The signal lost between a point just outside a building and a point inside it, in decibels. Every 10 dB is a factor of ten in power.
• DAS, distributed antenna system. Antennas spread through a building and fed from one or more carriers’ signal sources. Passive systems carry radio signals over coaxial cable, active ones over fibre or Ethernet.
• Neutral host. A system in a building or venue that serves several carriers’ customers and is owned by someone other than those carriers.
• MORAN and MOCN. Two ways to share a radio network. MORAN shares the radios while each carrier keeps its own spectrum; MOCN shares the radios and the spectrum, which is what a CBRS neutral host does.
• SNPN and PNI-NPN. 3GPP’s two kinds of private network: stand-alone, run without a carrier’s core, or public-network-integrated, built on a carrier’s network.