Potential Spectrum Interference Associated with Military Land Mobile Radios.
To address homeland defense needs and comply with government direction that agencies use the electromagnetic spectrum more efficiently, the Department of Defense (DOD) is deploying new Land Mobile Radios to military installations across the country. The new Land Mobile Radios operate in the same frequency range--380 Megahertz (MHz) to 399.9 MHz--as many unlicensed low-powered garage door openers, which have operated in this range for years. While DOD has been the authorized user of this spectrum range for several decades, their use of Land Mobile Radios between 380 MHz and 399.9 MHz is relatively new. With DOD's deployment of the new radios and increased use of the 380 MHz-399.9 MHz range of spectrum, some users of garage door openers have experienced varying levels of inoperability that has been attributed to interference caused by the new radios. Nevertheless, because garage door openers operate as unlicensed devices, they must accept any interference from authorized spectrum users. This requirement stems from Part 15 of the Federal Communications Commission (FCC) regulations. Garage door openers and other unlicensed devices are often referred to as "Part 15 devices." Congress requested that GAO review the potential spectrum interference caused by DOD's recent deployment of Land Mobile Radios. Specifically, Congress asked us to (1) determine the extent of the problem of spectrum interference associated with the recent testing and use of mobile radios at military facilities in the United States, (2) review the efforts made by DOD during the development of its Land Mobile Radio system to identify and avoid spectrum interference, and (3) identify efforts to address the problem.
Since DOD began its rollout of the new Land Mobile Radios in 2004, a number of complaints have been reported at several locations near military installations--notably, Eglin Air Force Base, Florida; Defense Distribution Depot Susquehanna (DDSP) near New Cumberland, Pennsylvania; and Ft. Detrick, Maryland. As of August 2005, manufacturers had received over 1,300 customer complaints of affected garage door openers that they attributed to interference from Land Mobile Radios. One major manufacturer also estimated that its distributors had received between 7,000 and 10,000 complaints. However, the extent of interference experienced by users of garage door openers from DOD's Land Mobile Radios is difficult to quantify because interference problems may not be reported or may be reported to several different organizations, including garage door opener manufacturers and retailers, government agencies, or congressional representatives. According to DOD and garage door opener manufacturers, the nature of the interference that has occurred varies by location. In some locations where the radios were rolled out, no occurrences of interference have been reported. Where interference has been reported, the problems range from intermittent inoperability to situations where the garage door may not open at all with the remote control device. DOD has reported a decrease of interference complaints. They attribute this decrease, in part, to consumer awareness of the problem and the completion of the Land Mobile Radio testing phase, at each site. In early 2005, following reports of interference, the National Telecommunications and Information Administration's Office of Spectrum Management and the FCC's Office of Engineering and Technology established a working group with representatives from DOD and the major manufacturers of garage door openers to develop short- and long-term solutions to the spectrum interference problem. The group has met several times, and as a result, DOD and the manufacturers report that progress has been made in terms of coordination and information sharing. For example, DOD has provided the Land Mobile Radio rollout locations to manufacturers and the ranges of spectrum to be affected through fiscal year 2010. DOD has also conducted analyses showing the likely extent of potential interference from Land Mobile Radios in several populated areas where the radios will be deployed and has given the findings to major manufacturers. For their part, manufacturers are offering retrofit kits to change the frequencies of existing garage door openers that would cost consumers $50 to $80, excluding installation. Furthermore, for new devices, one manufacturer is moving off of the 390 MHz spectrum range, and another plans to go to a multi-frequency approach using 390 MHz and other spectrum in order to minimize potential interference problems in the future.