Land Mobile Radio System

From Wikipedia, the free encyclopedia

Land Mobile Radio System (LMRS) is a term that denotes a wireless communications system(s) intended for use by terrestrial users in vehicles (mobiles) or on foot(portables). Such systems are used by emergency first responder organizations, public works organizations, or companies with large vehicle fleets or numerous field staff. Such a system can be independent, but often can be connected to other fixed systems such as the public switched telephone network (PSTN) or cellular networks. Also called Public Land Mobile Radio or Private Land Mobile Radio.

The Land Mobile Radio System is also the United States Department of Defense's new state-of-the-art communication system. Government contractors, such as Thales, Harris, and Motorola, provide the latest in LMRS technology to the government and military.

In November 2005, many automatic garage doors in Ottawa, Canada, have suddenly, [1] and strangely, stopped working, due to a powerful radio signal that appears to be interfering with the remote controls that open them. [2]

In the Summer of 2004, Garage door operators noticed similar phenomena around U.S. military bases. The strong radio signals on the 390-megahertz band simply overpower the garage door openers. One technician likened it to a whisper competing with a yell.[3]

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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.

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-- Government Accountability Office report GAO-06-172R [4]