FCC Approves Long-Awaited Wireless Multichannel Audio System Rules
FCC commissioners unanimously approved an order allowing wireless multichannel audio system (WMAS) use, a technology of special interest to wireless mic companies and users. The vote came Thursday during the commissioners' open meeting. Agency officials said the order was tweaked to address broadcasters' concerns, but power levels proposed in the draft order weren’t changed.
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The FCC has considered WMAS for years, with commissioners approving an NPRM in April 2021 and asking a battery of questions about the technology (see 2104220056). Wireless mic maker Sennheiser filed a petition with the FCC in 2018 seeking a rulemaking on WMAS (see 1808170045).
NAB, Fox and Paramount said in a filing last week, in docket 21-115, the proposed 100 mW power level for unlicensed systems presents “a high risk of interference to broadcasters’ existing licensed wireless microphones.” The proposed power level “is double the level proposed in the NPRM and appears to be justified solely to ‘allow manufacturers with different system designs …. to market unlicensed WMAS systems,’” they said. Broadcasters declined comment Thursday.
Wireless mics “are everywhere,” said FCC Chairwoman Jessica Rosenworcel during the meeting. They share spectrum with broadcasters, aeronautical operators, Wi-Fi and other unlicensed technologies, she said: “Making sure all of these services can function at the same time without interference is a tall task. So, when a new technology comes along with the potential to improve the efficiency of wireless microphone operations, it deserves attention.”
Commissioner Anna Gomez said the change was needed. She cited the more than 5,000 wireless mics employed at Sunday's Super Bowl. Commissioner Brendan Carr said he was happy to see the FCC move forward on an item addressing spectrum.
Sennheiser “started development of its WMAS over ten years ago,” said a news release. At that time, the company demonstrated a prototype system in front of the FCC’s Office of Engineering and Technology, Sennheiser said: “During the past five and a half years, the FCC monitored further developments of WMAS technology and concluded that it justified the requested rule change.”
Conventional wireless mics are limited to a bandwidth of 200 kHz, Sennheiser said. “Each audio channel uses a dedicated, mono-directional transmitter-receiver pair tuned to a unique RF carrier,” the company added: “The benefits of WMAS technology are accomplished by multiplexing audio channels onto a wideband RF channel. … Portable bidirectional transceivers will be able to communicate with a base station at an extremely low power spectral density of 50 mW for all transceivers together.”
“This is a great decision by the FCC to provide many microphone users across America with added flexibility,” Prakash Moorut, global head-spectrum and regulatory affairs at wireless mic company Shure, said in an email. “Allowing unlicensed WMAS with power up to 100 mW -- twice the power allowed for narrowband wireless microphones -- is a big benefit for many individuals, organizations, and small businesses,” Moorut said.
“WMAS will enable more wireless microphones to operate in the spectrum available (i.e., more microphones per megahertz of spectrum), which provides additional options when more microphones are needed,” said an FCC news release: “The rules do not alter the existing spectrum rights or expectations regarding spectrum access and availability as it relates to other authorized users that share the frequency bands with wireless microphone operations.”