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Defective scanner responsible for poor white space prototype performance, says Microsoft

The inability of a white space device known as Prototype A to reliably and consistently detect the presence of DTV and wireless microphone transmissions during tests used to compile a July report from the FCC Office of Engineering & Technology was due to a damaged scanner in the device that operated at a severely degraded level, Microsoft told the FCC in an Aug. 13 ex parte filing.

Microsoft, which submitted Prototype A to the commission for testing as part of an FCC effort to determine whether it’s feasible to allow non-licensed devices to use unoccupied TV channels in a given geographic region, determined the scanner was faulty during meetings with members of the OET Aug. 9 and 10, it said.

The filing said a “spare Prototype A device previously provided to the FCC Laboratory … reliably detected occupied television channels at -114dBm.” The commission is seeking information to determine whether or not white space devices using detect- and-avoid technology to prevent interference should be required to find signals as low as -116dBm.

According to the filing, during the meeting with commission staff, Microsoft representatives found Prototype A “left room for improvement” with respect to detecting wireless microphones, the filing said. Representatives from the commission and the company discussed ways to improve its ability to detect wireless mics. After fine-tuning the wireless mic detection algorithms used by the spare Prototype A, preliminary test found the “device detected wireless microphone signals at power level of -114dBm.”

Jack Krumholtz, Microsoft managing director, federal government affairs, released a statement coinciding with the FCC filing in which he said the company remains “confident that the unused channels in the television spectrum band can successfully be used without harmful interference to incumbent licensees such as television and wireless microphone services.”