Editor's note: This story was updated at 3:15 p.m. Jan. 18, 2007. Please go to Corrections & Clarifications to see what has changed.
The Transportation Department kicked off a public comment period that could determine the fate of a Global Positioning System backup system viewed by industry officials as essential for communications network timing signals and electronic navigation.
DOT said in a Federal Register notice published Jan. 8 that it wants comments on whether to shut down the ground-based long-range radio navigation (Loran) system operated by the Coast Guard or to develop a fully deployed enhanced Loran (eLoran) system that could serve as a GPS backup. Comments are due Feb. 7.
DOT said it is also working with the Homeland Security Department, which includes the Coast Guard, to determine whether investments made so far now merit consideration of eLoran as a complementary electronic system to GPS. The Coast Guard has spent $160 million on Loran modernization since 1997.
Chuck Norman, chief design engineer for network strategy at Sprint Nextel, said timing signals are crucial to the operation of complex wired and wireless networks. He said carriers worldwide use GPS for network timing signals, but they need a backup in case of a GPS outage or if GPS signals are jammed.
Norman said the Alliance for Telecommunications Industry Solutions (ATIS), whose membership includes all the telecom carriers in the country and equipment vendors, views eLoran as the “only viable alternative to GPS for providing [Coordinated Universal Time] of day and frequency accuracy that is suitable for a telecom primary reference source.” This endorsement of eLoran is contained in an ATIS paper he authored and submitted to the National Institute of Standards and Technology.
Sprint uses Loran and atomic clocks as backup to GPS in case of an outage, but Norman said atomic clocks provide only a frequency reference and not a time of day reference. Without accurate timing, network performance could degrade anywhere from eight hours to three days, Norman said. Consequently, someone may be able to place a call using a cell phone while stationary, only to have it dropped when mobile because handoff from one cell site to another relies on accurate timing.
Loran stations house two low-frequency transmitters. Receivers determine their location based on the time difference between the signals received from the two transmitters. The U.S. Loran system covers all coastal waters in the continental 48 states and parts of Alaska.
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