AES NY 2018 Preview: New RF Reallocation Looms

T-band spectrum to be cleared for commercial use

The ink is (mostly) dry on the RF-spectrum reallocation in which the FCC auctioned off most of the 600 MHz band over the past two years. The process drastically decreased the RF spectrum available to wireless-microphone users and followed a 2008 auction that did the same to the 700 MHz band. Now another spectrum auction is nearing its threshold.

The Middle Class Tax Relief and Job Creation Act of 2012 (Public Law 112-96) requires the FCC to recover and auction UHF spectrum between 470 MHz and 512 MHz, currently in use mainly by public-safety agencies, for commercial use by February 2021. Public-safety operations must be cleared from this portion of the band within two years of auction close. Known as the T-band, this frequency range provides a significant number of channels to support public-safety operations in 11 of the largest U.S. metropolitan areas, including Chicago, Los Angeles, Miami, New York, and Washington.

T-band reallocation and other RF-spectrum challenges will be discussed at the RF Super Session panel at AES New York 2018.

The law requires T-band licensees to migrate to other, unspecified spectrum. However, insufficient alternatives leave few options for identifying replacement spectrum: the VHF and UHF bands have few available channels. Also, the Nationwide Public Safety Broadband Network (NPSBN) is not yet available to support existing mission-critical voice operations displaced by T-band reallocation.

Lack of RF Coordination
The T-band reallocation will not be nearly as traumatic as the previous two displacements: the range is outside the frequencies most commonly used for wireless-microphone uses for entertainment, broadcast, and corporate applications. However, some wireless intercom systems may also use that range, with the most forward-thinking already using 470 MHz-512 MHz for receive only, according to one source. Like the public-safety users affected, though, they would have to find new frequencies.

According to Henry Cohen, spectrum manager, CP Communications/senior applications engineer, Radio Active Designs, the T-band reallocation is still an unknown proposition. So are several other challenges following the 600 MHz auction, including not knowing all spectrum buyers’ intentions for their recently purchased spectrum; an exception is T-Mobile, the biggest buyer, which has already begun using much of its spectrum.

The situation is compounded by the absence of any geo-location White Space database operators in the new RF landscape. “The databases were mandated for five years, and that time frame has expired,” Cohen says. “Apparently, they were unable to monetize that.”

Joe Ciaudelli, director, U.S. spectrum affairs, Sennheiser, notes that all the web portals for that function of the original White Space database administrators — including Spectrum Bridge, Key Bridge, Telecordia, Microsoft, and Google — have gone dark.

“Apparently, each failed to realize a viable business model,” he says. “For the moment, there is no active White Space database administrator. The database system is supposed to be the authoritative tool to determine channel available for wireless-mic operators throughout the 600 MHz transition period, as well as protect licensed mic operators against interference from existing White Space devices. This is very concerning. No doubt that this was the reason the FCC extended the waiver of the push-notification requirements through March 31, 2019.”

Continued Spectral Vulnerability
In a larger context, the T-band reallocation underscores the ongoing consolidation of spectrum available for wireless-microphone users, licensed and unlicensed, and the vulnerability of that left in the wake of the auctions, which are intended to supply more spectrum for the explosive growth of consumer wireless devices.

“White Space devices are beginning to show up in our already very crowded 500 MHz spectrum,” warns Jackie Green, president/CTO of wireless-systems developer Alteros. “The protection that was promised to Part 74 [that is, professional] users is nonexistent.”

She adds that the T-band reallocation has been waiting in the wings since 2012 but its potential impact had been masked by the larger 600 MHz auction.

“No one was paying much attention to it,” Green says. “The 600 MHz auction was such an elephant on the table, and 2020 felt like a long time away.”

The next spectrum displacement will immediately affect most wireless-microphone users. However, she says, it and others will ultimately impair the quality of remaining available spectrum.

“The T-band is immediately adjacent to the little amount of spectrum we have left in the 500 MHz band, as [artifacts] like harmonics and [intermodulation] begin to be felt,” Green explains. “We’re getting sandwiched in there, and there’s not much ‘there’ left.”

Green, Cohen, Ciaudelli and others will discuss this and other RF-spectrum challenges at the AES New York’s RF Super Session panel at 2:30 p.m. on Wednesday, Oct. 17.