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.
This paper is the first publicly released effort examining the use of Loran technology to support 5G telecommunications. The general concept was discussed in a 2016 paper by the Alliance for Telecommunications Industry Solutions’ (ATIS) Synchronization Committee. Based on the paper, ATIS in 2017 encouraged members of Congress to pass legislation that would become the National Timing Resilience and Security Act of 2018 (NTRSA).
There are tradeoffs. Opshaug and Tuck’s proposal would replace the legacy Loran standard signal with a new one.
“I was in the midst of developing proposals for the 3GPP standards organization when I first heard about the NTRSA,” said Opshaug. “5G seemed like exactly the kind of critical infrastructure that could benefit from a backup timing solution.”
“We wanted to bring some of the ideas used to develop 5G position and timing to Loran,” said Tuck. “Using Loran as the timing synch could enable 5G to improve overall infrastructure resilience.”
Yet, as with most things, there are tradeoffs. Opshaug and Tuck’s proposal would replace the legacy Loran standard signal with a new one. This would require redesign of receivers and some transmitters. The proposal could support denser deployments to further improve resiliency.
“The new signals seem incompatible with existing receivers and Loran networks,” according to Professor Jiwon Seo of South Korea’s Yonsei University. South Korea is upgrading its Loran-C network to the eLoran standard. The new South Korean system will be compatible with neighboring Russian and Chinese Loran systems, so users will be able to benefit from signals anywhere in East Asia. Until 2010 signals from the U.S. Loran system cooperated with these networks as part of the Far East Radionavigation Service (FERNS).
Navigation expert Logan Scott is intrigued by the proposal but observes that more work needs to be done. “This is an interesting waveform,” he said, though he had questions about the propagation channel, antennas, and possible distortion.
The authors acknowledge that much more needs to be done, including better determining timing and positioning accuracy.
Yet they and others see potential in combining the very different phenomenologies of low frequency, 100KHz Loran and 5G telecommunications which typically operate in the gigahertz range.
Opshaug and Tuck’s paper LORAN-5G can be accessed here.
