Performance of Loran-C 9th pulse modulation techniques
Date of Original Version
In 2001, the Volpe National Transportation Systems Center completed an evaluation of GPS vulnerabilities and the potential impacts to transportation systems in the United States. One of the recommendations of this study  was for the operation of backup system(s) to GPS; Loran-C was identified as one possible backup system. The Federal Aviation Administration (FAA) has been leading a team consisting of members from industry, government, and academia to evaluate the future of Loran-C in the United States with respect to position, navigation, and timing applications (specifically, non-precision approaches for aircraft, harbor approach and entrance for ships, and Stratum 1 frequency and timing). One component of this system development is adding the capability to transmit data messages supporting these applications on the Loran signal itself, frequently called the Loran Data Channel (LDC). Data transmission on the Loran signal is not a new idea; the Coast Guard experimented with a pulse-position modulated data communication system code named Clarinet Pilgrim in the 1960s. However, the use of advanced DSP-based techniques for receivers, combined with new equipment installations at the U.S. Loran transminer sites now offers the opportunity for a reliable, higher rate data transmission system. During 2000-2003 a Loran Data Channel that employed phase modulation on 6 of the 8 Loran pulses in a group, called Intrapulse Frequency Modulation (IFM), which achieved a data rate of 250 bps was experimented with. Currently, pulse position modulation of a 9th pulse is being developed. Recently, the Loran Support Unit in Wildwood NJ has been transmitting 9th pulses on their experimental rates. This paper reports on performance evaluation of receiving these test messages at the Coast Guard Academy in New London, CT. Specifically, we look at raw channel symbol error rates (due to cross-rate interference and channel noise) and bit error rates after Reed Solomon decoding.
Proceedings of the Institute of Navigation, National Technical Meeting
Hartshorn, Lee, Peter F. Swaszek, Gregory Johnson, Mark Wiggins, and Richard Hartnett. "Performance of Loran-C 9th pulse modulation techniques." Proceedings of the Institute of Navigation, National Technical Meeting 1, (2006): 384-395. https://digitalcommons.uri.edu/ele_facpubs/1072