Phil Kurz /
03.25.2009 11:10 AM
Originally featured on
SBE asks FCC to reconsider white space order, finds wireless mic protection lacking

The Society of Broadcast Engineers asked the FCC March 19 to reconsider rules it established last year to allow unlicensed devices to operate in TV band white spaces, saying the Report and Order authorizing the devices does not provide sufficient protection and lacks detail in critical areas.

The SBE asked the commission to reconsider seven specific areas of the order, ranging from the 40mW adjacent channel power limit for personal/portable white space devices to the protections it set up for wireless microphone and video assist devices used for electronic newsgathering.

In the filing, the society told the commission that given the importance of over-the-air broadcasting and other incumbent services, such as wireless mic use and ENG, and the impossibility of remedying interference problems once white space devices are in the hands of millions of people, the commission must get the technical requirements for white space devices right from the very beginning.

As relates to protection for wireless mics, a major concern has been the ability of spectrum-sensing technology envisioned for white space devices to locate wireless mics being used in the vicinity and avoid operation on the same or adjacent channels. In the filing, the SBE said the commission’s own test data “clearly show” sensing technology has failed during testing and thus does not offer protection from interference.

Pointing to FCC reports describing the performance of prototype devices as relates to sensing the presence of wireless mics, the filing used the commission’s own words to raise serious doubts. Quoting one commission report, the filing said the FCC’s “measurement studies found that while the prototype devices were generally able to detect ‘clean’ TV and wireless microphone signals on a channel with no other signals present, their ability to reliably detect unoccupied channels degraded to levels we consider unsatisfactory when the test signals included multipath and other fading effects and when signals were present on other channels.’”

In the view of the SBE, the FCC’s decision to authorize unlicensed white space devices “provides false assurances of reliability,” according to the filing. It appears the FCC has “abandoned providing adequate protection to critical, incumbent wireless microphone operations and TV viewers so that WSD manufacturers can save money,” the filing said.

The society asked the commission to increase the number of “safe harbor” channels set aside for wireless mics from the two currently in place, and told the commission it should extend the reach of these safe harbor frequencies from the 13 markets established in the order to nationwide coverage.

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