Blog Editor’s Note: This paper is another reminder that PNT is infrastructure for a host of technologies, including telecommunications. The better, more resilient the PNT, the better, more resilient our telecoms. This has been a theme at the ATIS Synch Committee since day one.
The recent DOT report to Congress on its GPS Backup Technology Demonstration said a system-of-systems approach (which we heartily support) is needed for PNT resilience. It also identified the needed systems saying:
“…those technologies are LF and UHF terrestrial and L-band satellite broadcasts for PNT functions with supporting fiber optic time services to transmitters/control segments.”
The leading candidate for the low frequency (LF) component seems to be eLoran or some variant.
As a side note, with all the controversy and competition for much higher frequency bands, it is good to see some focus on use of lower frequencies. An example of “spectrum efficiency”?
A new paper by two Qualcomm engineers imagines restructuring Loran technology to more easily incorporate timing signals into telecommunication systems.
The paper, titled simply “LORAN-5G,” was authored by Guttorm Opshaug and Dave Tuck. It envisions moving away from legacy pulsed signals to a more continuous wave form which would allow significantly lower power transmissions.
According to Opshaug, “Another big advantage that may not be as apparent, is the built-in orthogonality in the signal structure of OFDM. This means that a receiver would be able to detect very weak signals from distant towers at the same time as receiving signals from a very strong close tower. Such robustness towards near-far effects is critical for terrestrial navigation use.”
Another change would be a marked increase in the capacity of the Loran data channel to more than 2.6kbps. “This could open opportunities for additional service options and/or reduce latency of existing ones,” according to Tuck.
UrsaNav CEO, Charles Schue, expressed great interest in Qualcomm’s paper. UrsaNav is a long-time provider of Loran equipment and consulting. “The intersection of PNT and communications discussed in the Qualcomm paper is exactly what is needed to ensure that PNT systems evolve and stay relevant,” he said. “In fact, we build our software defined transmitter and receiver solutions to specifically include the ability to produce and use these types of signals.” A Cooperative Research and Development Agreement between UrsaNav and the Department of Homeland Security demonstrated these type of potential upgrades in 2012.