Possible optimizations for the US Loran system
Date of Original Version
The United States has a significant capital investment in the current Loran system in its 24 stations and towers nationwide. As the existing system was developed in the 1970's, the question arises: Is it possible to re-use the existing infrastructure to better serve the position, navigation, and timing communities given today's technologies? As a terrestrial radionavigation system at 100 kHz, Loran provides a good complement to the GPS system in that it is not subject to the same vulnerabilities and failure modes. In this paper we re-examine the potentials of Loran, reopening some of the degrees of freedom in the design process. While we keep certain hard constraints - tower locations, station power levels, and spectrum - and, for now, impose the limits of a pulsed system using the existing antennas, we investigate several options: What is the improvement gained by assuming that all stations are time-synchronized (TOT control) and that receivers make use of both rates of dual-rated stations to improve TOA estimates? What is the improvement to be gained by single-rating all stations? If we keep the fastest rate at each station, how does this improve performance? For this option we look at the improved SNR due to decreased transmitter jitter when single-rated, no cross-rate blanking at the transmitter, and reduced cross-rate interference as compared to the reduced number of pulses available under option 1. We re-examine chain assignments; the trade-offs are maintaining sufficient pulse rate while minimizing cross-rate interference. After single-rating, what improvement do we get from changing the number of chains? Future options to consider are changing the pulse characteristics including shape, number, and phase coding. © 2006 IEEE.
Record - IEEE PLANS, Position Location and Navigation Symposium
Johnson, Gregory, Mark Wiggins, Peter F. Swaszek, Lee Hartshorn, and Richard Hartnett. "Possible optimizations for the US Loran system." Record - IEEE PLANS, Position Location and Navigation Symposium 2006, (2006): 695-704. doi:10.1109/PLANS.2006.1650663.