Broadcast associations oppose ‘interference temperature’ approach under consideration

The Association for Maximum Service Television (MSTV) and the National Association of Broadcasters (NAB) filed comments May 5 with the Federal Communications Commission opposing the proposed use of an interference temperature approach to spectrum sharing.

The comments were filed in response to a Commission Notice of Inquiry and Notice of Proposed Rule Making regarding interference temperature. Interference temperature refers to the establishment of a threshold for interference below which devices can safely share spectrum.

In their comments, the associations said “not a single commenter” supported the interference temperature approach the commission favored and that only a “handful of parties” offered “qualified support.”

“The comments recognized that the proposed interference temperature concept is fraught with technical challenges that make its implementation impractical and potentially disastrous,” the associations said. “Tellingly, even proponents of unlicensed devices — those that stand to gain from unlicensed underlay operations that the interference temperature approach seeks to permit — recognize that the interference temperature approach suffers from significant technical flaws and is not viable.”

A majority of those commenting on the interference temperature approach found fault with the proposal because of the possible harm unlicensed devices would cause if operated in licensed spectrum bands, the associations said. Problems stemming from measuring interference temperature accurately are likely to licensed services because they possibly face harmful interference and loss of signal.

“Several commenters also agreed with MSTV and NAB that once unlicensed devices are introduced into licensed spectrum bands, they will be impossible to locate and control should they cause interference,” they said. “The broadcast spectrum bands are particularly ill-suited for unlicensed underlay operations in part because broadcasters do not control the technical characteristics of TV and AM/FM receivers. Broadcasters will, therefore, be powerless to even attempt to solve interference problems caused by new unlicensed devices.”

The associations also questioned the wisdom of pursuing this approach in light of television broadcasters’ transition to DTV and the transition of radio broadcasters to In Band On Channel digital technology.

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