Controversy Flares over Interference to Unlicensed Devices

Unlicensed device users at 902-928 MHz challenge LMS provider Progeny’s test results.

We reported back in February about a licensed service provider being required to demonstrate that its operation would not cause unacceptable interference to unlicensed devices. This is unusual. The FCC rules ordinarily require an unlicensed device to accept any and all interference from any source. But certain technologies used in the licensed Location and Monitoring Service (LMS) at 902-928 MHz are uniquely subject to a reversal of the usual priority. Those LMS licensees must demonstrate through actual field tests that their systems do not interfere with unlicensed devices.

When the FCC recently granted a technical waiver to LMS provider Progeny, it specifically required field tests to show that the waivered system does not cause unacceptable levels of interference to unlicensed devices in the same band. Among the thousands of unlicensed applications in the band, the FCC mentioned “smart grid” applications, including remote meter reading and utility load management, as well as cordless telephones and wireless local area networks. Other unlicensed uses of the band include wireless Internet access, ZigBee industrial controls, and a vast host of wireless consumer devices.

Progeny has since filed its test report. But commercial users of unlicensed devices have come forward to criticize the study. (Consumer devices, such as cordless phones, may have a similar potential for interference, but so far consumers and their advocates have remained silent.) Progeny, the commercial users say, used too few unlicensed devices, the devices Progeny used were non-representative, and the conditions used in the testing were artificially rigged to understate interference. Samples of such critical comments may be read here, here, and here. Progeny, needless to say, disagrees with its critics.  (Interested readers may find the entire FCC docket by searching for Docket No. 11-49 at the FCC’s ECFS webpage.)

Although the comment cycle on Progeny’s test report has officially closed, the FCC is accepting ex parte filings. But not for long; we expect a decision soon. Those interested in either challenging or supporting Progeny’s test results should do so promptly.

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