A coalition including Charter Communications, WISPA and public interest groups are urging the Federal Communications Commission (FCC) to reject proposals to increase power limits in the shared CBRS band, saying it would favor macro cell deployments only and jeopardize existing deployments.
Other signatories on the July 1 letter (PDF) voicing strong opposition to changes in the band include the Open Technology Institute, Public Knowledge, the Consortium for School Networking, and the Schools, Health & Libraries (SHLB) Coalition.
The 3.5 GHz Citizens Broadband Radio Service (CBRS) band has a unique sharing paradigm that includes incumbent federal operations, priority access licenses (PALs), and general authorized access (GAA). The band was designed with lower power limits, as well as smaller county-sized licensing scheme for PALs.
Dish Network earlier this year (PDF) provided technical analysis in asking for a new Public Notice that would seek input on raising the maximum authorized power limits for CBRS, saying current rules limit the viability for macro cell 5G deployments in the band.
Notably, Dish spent nearly $1 billion to secure CBRS PALs and is working to build its own 5G network.
CBRS sits between the recently auctioned C-band (3.7-3.98 GHz) and the 3.45-3.55 GHz band coming up for auction later this year – both which have higher power limits. By not aligning with the adjacent bands, Dish argued CBRS PAL holders face a competitive disadvantage. Higher power and a new device class wouldn’t harm incumbents, GAA users or fair and dynamic use of the spectrum, Dish asserted.
However, the coalition takes a different view.
It raised concerns arguing a change would undermine existing deployments, cause interference for both PAL and GAA users, impact fixed wireless service, and potentially endanger incumbent users like the DoD.
While not the highest grossing, the FCC auction for CBRS PALs had 228 winning licensees, including a mix of entities with nearly 70 smaller wireless internet service providers (WISPs) securing spectrum – which many considered a success for what is sometimes dubbed “the innovation band.”
Charter was the third-largest spender at the CBRS auction, bidding $464 million while WISPA members spent $100.4 million
The coalition asserts that allowing higher powered operations would “fundamentally alter the nature of CBRS” and the objective to create a flexible band for a variety of use cases. It pointed to existing deployments using CBRS to provide rural broadband, IoT deployments in factories, and private networks delivering connectivity to schools and libraries.
The coalition also warned of additional interference to PAL operations and less utilization of the spectrum as GAA use is jeopardized.
“Such a result would disrupt the diverse and innovative service currently being deployed and inhibit future competition throughout the band,” the coalition wrote.
The FCC, they noted, already considered and rejected proposals for higher power limits. And since existing power levels are best suited for small cells, CBRS users have already designed networks with that in mind, with a mix of PAL and GAA use.
The group cited extensive deployments in the band (with almost 150,000 CBRS Devices deployed and more than 130 CBSD models and 200 consumer devices) and said changing rules for CBRS could undermine those due to increased interference from macrocells.
“To overcome an increase in interference from nearby higher power base stations, these [small cell] networks would have to increase their own transmit power levels, but cannot because they are limited to their currently deployed small cell limits,” the coalition wrote.
Interference from devices on nearby, but not overlapping frequencies would also reduce small cell networks’ coverage and service throughput for PALs – as the Spectrum Access System (SAS) administrator only is obligated to protect against interference when CBRS devices are operating on the same frequency.
It would be an issue for GAA users as well, the coalition says, as higher power would mean both GAA and PAL CBRS devices cover larger areas – so more overlap between the two. To reduce interference, the SAS would need to move GAA operations to other channels and provide a larger projection area for the higher-operating PALs.
“These accommodations due to the higher power levels would effectively allow macrocells to ‘claim’ more spectrum coverage” giving more advantage to higher power networks versus small cells, the group stated. “Moreover, the shrinking of available spectrum for GAA operations would cascade as neighboring PAL operators increase their own transmit power levels to safeguard against interference.”
Fixed wireless networks in rural areas could be impacted, as providers wouldn’t be able to take advantage of higher power levels in part because existing user equipment doesn’t support it, the coalition said.
T-Mobile in earlier FCC filings had expressed criticism for higher CBRS power levels, and Dish’s proposal specifically. In a March ex parte (PDF), the carrier wrote that “the innovative nature of the CBRS band is premised on low-power use of the spectrum over limited geographic areas.”