NAB Comments on FCC Interference Testing Procedures

By: Dan Daley, Audio Editor, Sports Video Group

The National Association of Broadcasters pulls few punches in comments on FCC procedures for testing for possible interference between the 600 MHz RF spectrum band, which the FCC plans to auction off next year, and existing DTV channels.

Released on Friday, the assessment criticizes the agency’s methodology, data, and assumptions, suggesting that the residual issues surrounding the loss of the 700 MHz band several years ago “pale in comparison to the potential problems associated with co-and adjacent-channel LTE and DTV operation in the 600 MHz band.”

The comments laud the FCC’s effort but pointedly state that the testing is too limited for statistical analysis. “The testing itself also suffers from a number of methodological issues,” the comments continue, “and the results of the testing generally do not support [the Office of Engineering and Technology]’s conclusions.

Other complaints include the following assertions:
“The Commission has given no indication that it has considered the numerous and substantial problems NAB and other broadcasters identified with the proposed methodology, which include incorrect assumptions about operating parameters for LTE operations, ignoring combined interference contributions, unprecedented use of inappropriate field strength prediction characteristics, and selective use of clutter loss, among others.”
“The Commission still has not provided clarity as to how it intends to use this proposed methodology, and how the methodology will fit into rules designed to prevent harmful inter-service interference following the auction.”

The trade organization states that transparency and added diligence in testing is necessary to protect both broadcasters and entities that acquire the auctioned spectrum.

“If over-the-air television viewers lose their signal due to LTE operations, or if wireless carriers … find themselves unable to actually deploy service where and how they expected in making billion-dollar decisions, the Commission’s methodology for predicting inter-service interference will have proven unsuccessful,” the NAB says. “Accordingly, while NAB supports additional testing and analysis, the Commission must move forward in a transparent process with proposing and seeking comment on specific rules for inter-service interference protection.”

Asserting that the data being used by the FCC to measure the potential for interference between spectrum users comprises “plainly inaccurate inputs and assumptions,” the comments endorse an approach based on proven separation distances as “far simpler and more appropriate.”

Sports broadcasters in particular are closely watching the process of spectrum reallocation because of its impact on the use of wireless RF microphones, which are critical for live-sports-programming operations and management. The loss of the 700 MHz spectrum in 2010 compelled pro audio and its broadcast customers to completely replace the hardware infrastructure of wireless audio. The auction of the 600 MHz band is expected to require even more-complex responses by manufacturers and broadcasters.