Performance of Loran-C 9th Pulse Modulation Techniques
Abstract
In 2001, the Volpe National Transportation Systems Center completed an evaluation of GPS vulnerabilities and the potential impacts. 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 to evaluate the future of Loran-C in the United States with respect to position navigation, and timing applications (specifically, nonprecision 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 transmitter 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2006
- Accession Number
- ADA575171
Entities
People
- Gregory Johnson
- Lee Hartshorn
- Mark Wiggins
- Peter F. Swaszek
- Richard Hartnett
Organizations
- United States Coast Guard Academy