Sharing C Band Complex, Many Agree: Carriers Want It for 5G; Current Users Cautious

Sharing the C band now used by satellite operators and by broadcast and other programmers sending content using it could be tricky, many stakeholders agree. Where they differ is on whether it should be repurposed or shared or mainly left as-is. True to predictions and comments posted through Thursday, even newer filings reveal differences between carriers on one hand and current users on the other (see 1805310058), a docket 18-122 review shows. A couple dozen filings were posted Friday, from tech companies, carriers, equipment makers, cable and content interests plus other industries.

AT&T, Verizon and T-Mobile said the FCC should make 3.7-4.2 GHz available for licensed commercial use to support deployment of 5G, as the agency prepares a report to Congress on the spectrum, also known as the C-band, as required by the Mobile Now Act. AT&T urged a sharing regime, noting it uses C-band fixed satellite services to offer connectivity to remote villages in Alaska, “to rapidly restore communications services in damaged locations like Puerto Rico after Hurricane Irma” and to acquire video content for its DirecTV and U-Verse customers. “AT&T is optimistic that there may exist opportunities for sharing the lower C-Band between FSS [fixed satellite service] and licensed mobile terrestrial operations,” the carrier said. “The FCC should thoroughly investigate regulatory options for allowing such use while still accommodating the existing and future needs of C-Band FSS users that rely on the band’s unique characteristics.”

Benefits exceed risks posed by opening the frequencies for licensed use, Verizon said. “The 3.7-4.2 GHz band contains more bandwidth than the Cellular, PCS, AWS-1, AWS-3, 600 MHz, and 700 MHz bands combined and is likely to be globally harmonized for mobile broadband,” the company said. “The U.S. telecommunications industry is in a global race to lead the world in 5G. The United States, however, is facing a mid-band spectrum deficit that could ultimately slow 5G deployment, particularly beyond dense urban areas.”

T-Mobile is seeking reallocation of the band for 5G. “Mid-band spectrum, specifically the 3.7-4.2 GHz band, is ideally situated for 5G because of the potential for international harmonization, the availability for large bandwidth channelization, and the band’s proximity to other spectrum being evaluated for mobile wireless broadband use,” it said. “The 3.7-4.2 GHz band also provides a balance of capacity and coverage.” Motorola Solutions said sharing is the best option. “While some advocates are promoting re-locating and re-banding incumbents for a portion of the band, such an undertaking would be costly and time-consuming, and would delay the introduction of innovative wireless services by several years,” the company commented.

Study Sought

NCTA and many other C-band users urged caution. The group and others said before the agency makes recommendations on how to proceed, proponents of expanded terrestrial wireless access should make technical analyses.

“As the race to 5G reaches the C-band," NCTA counseled "the Commission to consider carefully the impact of proposed new terrestrial wireless uses of the 3.7-4.2 GHz downlink on the extensive incumbent operations in the band.” The association's members use the spectrum to deliver programming, it noted. "Many unanswered questions remain to be addressed regarding proposals for band segmentation or co-channel sharing."

NPR seeks preservation of "critical existing and planned non-Federal capabilities, including the Congressionally sanctioned longstanding and planned future use of a small portion of the spectrum by the Public Radio Satellite System.” PRSS "is completely dependent on extremely low-power satellite-to-earth station C-band downlinks, which are particularly susceptible to interference," NPR said. It asked staff to "consider allocating a limited portion of the C-band for exclusive use by commercial wireless services and reserving the remaining C-band spectrum for exclusive fixed satellite use."

The frequencies are key to 5G, but sharing isn’t a viable option, CTIA wrote. “There are myriad ways to enable repurposing while ensuring that existing users of the band can continue to receive their services, including repacking existing operations into a smaller portion of the band, relocating to other spectrum, moving to remote areas, and transitioning to another medium such as fiber,” said CTIA. “Mid-band spectrum is increasingly viewed as a key component to unlocking the benefits of 5G connectivity.”

Sharing Concerns

Satellite operators and allies said co-frequency sharing of C-band isn't feasible.

Intelsat, SES and Intel said thousands of FSS earth stations would need "significant" protection zones around them, with debate about such zones sure to be "technical, contentious and lengthy." Eutelsat also said such sharing would require large exclusion zones, band partitioning "or other preclusive measures" aimed at protecting satellite links from interference. Those separation distances would have to be "tens to hundreds" of kilometers, the Satellite Industry Association said.

Eutelsat said it's evaluating the Intelsat/SES/Intel plan for clearing part of the band, and it may be acceptable as long as there's "sufficient" compensation to it and its customers for expenses and opportunity losses, though doing more than 100 MHz of the band isn't achievable. It said a voluntary process to allow wireless use of the band can't be allowed to result in compulsory band clearing. Intelsat/SES/Intel said the band-clearing plan would provide "clean" spectrum for terrestrial mobile. SIA and others also challenged the BAC's proposal for fixed point-to-multipoint services, saying the coalition hasn't explained how such operations could adjust fast enough to accommodate the frequency or orientation shifts of receive earth stations.

CBS, Disney, 21st Century Fox, Time Warner, Discovery, Univision and Viacom said the FCC should “emphasize the need to protect the integrity of existing services.” IHeartMedia agreed, saying the agency needs to prevent “disruption to incumbents.” Since there’s “substantial record evidence” on the possibility of harmful interference to C-band downlinks, the commission should find “that it is not feasible to introduce new co-channel or similar forms of sharing into the spectrum reserved for video delivery,” the content companies said.

Aviation Worries

Aviation interests also expressed concerns. Many called for the FAA and National Transportation Safety Board to have input before the FCC allows commercial wireless in the 3.7-4.2 GHz band given its heavy use by aviation interests for navigation, satellite communications and other applications.

Given aviation use of the 4.2-4.4 GHz band for wireless avionics intra-communications and radio altimeters, use of the adjacent band for mobile wireless service needs to proceed "with the utmost caution," with radio altimeters needing protection from harmful interference, Boeing said. It said altimeters -- used in functions ranging from precision approach and landing to collision avoidance -- operate at low power levels and thus are at risk from ground-based radio transmitters in an adjacent band. "It would make little sense to aggressively cannibalize" satcom spectrum for capacity that could be fulfilled by other bands, such as the upper bands, Aviation Spectrum Resources said. UPS said its airline operations rely on the 3.7-4.2 and adjacent 4.2-4.4 GHz bands, and that incumbent services like aviation weather data backhaul and radio altimeters need protection. The FCC needs to avoid "any encroachment" on the frequencies used by radio altimetry, Airlines for America said. Delta said any altimeter interference, "no matter how brief," is a safety issue since altimeter problems can affect autopilot or ground proximity warning systems.

Satellite truck operator Satellite Technology Systems said numerous mobile satellite truck companies that use C-band uplinks to cover events would face business jeopardy from terrestrial interference. It said if there's to be implementation of the satellite C-band clearing plan, proceeds need to be shared "with ALL the displaced" users.

The National Translator Association questioned the legality of procedures on sharing the band. The FCC provided less than a full month for comment, and the comment deadline coincides with an important filing deadline for broadcasters, NTA said. “It is fair to ask whether any action adopted pursuant to this record, compiled under these circumstances, may be said to comply with requirements for a rule making in the Administrative Procedure Act.”

The FCC should amend its rules to permit increased use of fixed links “on a non-interfering basis” with fixed satellite services, said Google. Once coexistence challenges between mobile and FSS are addressed, the agency should allow “exclusively licensed flexible use,” Google said. Fixed links should be repacked into the rest of the band “and/or coordinated with mobile and other exclusive flexible uses on a shared-spectrum basis,” the company said. “Clearing FSS uses from some or all of the 3.7 to 4.2 GHz band may be the only realistic option.” Nokia said that “the highest and best use of the 3.7-4.2 GHz range is terrestrial 5G, not FSS uses which are in decline and have alternative paths to serve the existing user base.”