'Duplex Gap' Could Be Affected by Spectrum Auction Participation

FCC clarifies impact of 'impairments' on clearing scenarios
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Slightly fewer TV markets would be affected by "duplex gap" impairments using an "alternative approach" for the broadcast spectrum incentive auction methodology, according to a message posted by the FCC Incentive Auction Task Force late Friday evening. 

Gary Epstein, chair of the FCC's Incentive Auction Task Force, issued alternatives to his group's simulations of spectrum-clearing scenarios. In charts showing that at each of three levels of spectrum clearing, channels in two to seven fewer markets would be affected by plans to protect the duplex gap, which is the guard band between the paired uplink and downlink frequencies. The notice was in response to requests for more information about how the duplex gap could affect the auction.

Epstein was careful to point out that, "The simulations reflect no assumptions about auction outcomes in terms of which reserve auction participants would be selected as winning bidders, the winning bid amounts ... or whether the Commission would be able to close the auction at the initial clearing target."

Attorneys tracking the FCC auction plans agreed that the "sunshine" disclosure offered no hints about the Commission's "Procedures Public Notice" of auction details, which is the first item on the agency's July 16 meeting agenda.

Epstein's message, posted after 6 p.m. on Friday, July 10, showed two approaches to each of the three scenarios that Commission has explored for assigning airwaves of potentially "impairing stations" to the 600 MHz band. In addition to the existing approach under which optimization software will assign stations to minimize impaired weighted-pops, the FCC is now proposing an alternative approach that minimizes impaired weighted-pops but restricts the software from assigning stations to channels that would impair the duplex gap.

The back-up documentation identifies the three scenarios as "moderate" participation (40% to 50% at 84 MHz clearing), "more robust participation" (50% to 60% at 114 MHz) and "high participation" (60% to 70% at 126 MHz).  The report explains that the impairment standard for clearing each target can affect adjacent markets.  Indeed the "nationwide impairment" level is slightly higher under the FCC's alternative approach, but less than a 4% variation in every scenario. Most of the markets affected are in border regions where interference may come from Canadian of Mexican stations.

The summary of FCC data included several assumptions, according to Friday's explanation:

  • The clearing target chosen for each scenario represents the highest achievable target under the one equivalent block impairment threshold
  • Protected only Canadian operating stations, but assumed they were fixed
  • Incorporated U.S.-Canada and Canada-U.S. ISIX data
  • Protected all allotments in Mexico – whether occupied by a station or not

Epstein's explanation came in response to recent requests from wireless carriers and others about how the impairments - which could restrict delivery capabilities - will be affected by the auction.  A communications attorney who has closely followed the process (but asked not to be identified) explained that the change in the duplex gap approach could actually take more TV stations off the air, thus potentially raising the value the spectrum during the auctions. He also noted that TV channels may be reallocated into the duplex gap in some markets, providing a more reliable use of spectrum than turning over those airwaves to unlicensed or licensed uses, such as Wi-Fi and wireless microphone suppliers. 

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