GPS World

Tag: CRADA

  • LORAN-5G: Paper envisions new use for venerable tech

    LORAN-5G: Paper envisions new use for venerable tech

    Image: KENGKAT/iStock/Getty Images Plus/Getty Images
    Image: KENGKAT/iStock/Getty Images Plus/Getty Images

    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.

  • The System: eLoran Gets Trials, Possibly a New Life

    eLoran Gets Trials, Possibly a New Life

    As result of a Cooperative Research and Development Agreement (CRADA) between the U.S. Coast Guard and UrsaNav, Inc., on-air tests are being conducted from the former Loran Support Unit site in New Jersey.

    One of the CRADA’s goals is to research, evaluate, and document a wireless technical approach as an alternative to GPS for providing precise time. The ability to obtain precise time to at least one microsecond is necessary for the proper operation and functioning of many critical industries and systems. Examples include telecommunications networks, banking and finance, energy and power delivery, emergency services, transportation systems, and military and homeland security systems.

    Additional on-air tests are planned at various sites throughout the United States. Broadcasts will test several different frequencies, waveforms, and modulation techniques using evolutionary, state-of-the-art technology. Reception of these broadcasts are planned at both on-shore and off-shore locations, and will include advanced LF data delivery techniques. The results of these trials will be presented at national and international conferences. Parties interested in any part of the trial, or interested in doing their own measurements, are invited to contact UrsaNav.

    The company has partnered with precise-time synchronization company Symmetricom and Nautel, supplier of high-power RF transmitters. According to UrsaNav, this “alliance of expertise” provides the foundation technology for a wide-area, terrestrial-based alternative to satellite systems such as GPS, GLONASS, and Galileo.

    For further background and commentary, see Don Jewell’s Defense e-newsletter for April.

    “Global government, industry, and academic experts recognize that advanced LF signals, of which eLoran is just one example, can provide alternative timing — either as a stand-alone service, or as a component of an existing positioning, navigation, and timing (PNT) service. The high-power, virtually jam-proof and spoof-proof LF signals operate independently of GPS and GNSS, and provide a Universal Coordinated Time (UTC) time reference in the order of tens of nanoseconds. The recognition of the criticality of time to many aspects of our national critical infrastructure has led to establishment of the CRADA to evaluate the benefits of an LF wide-area timing system.”

    The LF signals can also be used as pseudoranges mixed in with GPS, or if enough transmitters are available, as a fully independent PNT network. In other words, a true backup PNT capability for safety-of-life navigation, for dispatching first responders, and for supporting critical national infrastructures.

    First Galileo PRS Signal Received

    Septentrio and QinetiQ, in close partnership with the European Space Agency (ESA) and their industrial partners, achieved the first successful reception of the encrypted Galileo Public Regulated Service (PRS) signal from the first Galileo satellites, launched in November 2011.

    The signal was received on the Galileo PRS Test User Receiver (PRS-TUR) jointly developed by Septentrio (Leuven, Belgium) and QinetiQ (Malvern, United Kingdom) under an ESA contract. For the reception test, the receiver was installed in the Galileo Control Centre in Fucino, Italy, and operated by technical experts from ESA.

    Septentrio and QinetiQ are long-term contributors to the Galileo Programme, working closely with ESA, the European GNSS Agency (GSA), and European industrial partners since 2003.

    Count Five Compass IGSOs

    The BeiDou-2/Compass G5 satellite launched on February 24 has achieved an initial approximately geostationary orbit.

    The current sub-satellite east longitude is 57.23 degrees. The intended final orbital slot may be 58.75 degrees, one of the previously announced orbital locations and one used by the BeiDou-1 demonstration system.

    GPS Use in FAA’s NextGen 2012 Plan

    An overview of NextGen benefits and accomplishments is available in the 2012 update to the NextGen Implementation Plan, published by the Federal Aviation Administration (FAA). 

    The 2012 NextGen Plan specifically mentions GPS/GNSS as follows:

    Performance Based Navigation (PBN). The current aircraft fleet is well equipped with PBN capability. In the air carrier community, the heart of the PBN capability is the Flight Management System, which uses input from multiple distance measuring equipment (DME), or from the GNSS using a GPS sensor or a GPS with Wide Area Augmentation System (WAAS) sensor.

    Ground Based Augmentation System Landing System (GLS) Enabler. This program researches use of differential GPS corrections to support Category III (Cat III) approaches. This capability will be the same as Cat III instrument landing system (ILS), without the need to restrict taxiing aircraft near antennas and at reduced cost to the FAA.

    Automatic Dependent Surveillance–Broadcast (ADS-B). Aircraft position (long-lat, altitude, and time) is determined using GPS, an internal inertial navigational reference system or other navigation aids. ADS-B Out involves transmission of a GPS position (or of comparably performing navigation equipment meeting integrity and accuracy requirements) from an aircraft to display its location to controllers on the ground or to pilots in other aircraft equipped with ADS-B In.

    Low-Visibility/Ceiling Approach. Localizer Performance (LP) with Vertical Guidance (LPV) Approaches. These are more cost-effective to implement compared to additional ground-based navigation aids (NAVAIDs) and their approach procedures. Increasing the number of LPV/LP approaches will provide further incentives for users to equip with GPS/WAAS. This will provide increased utility to the more than 40,000 general aviation aircraft that are already WAAS-capable. The FAA will also deliver LP approaches to runways that do not qualify for LPVs due to obstacles.

    Ground Based Augmentation System (GBAS) Precision Approaches. GPS/GBAS support precision approaches to Cat I and eventually Cat II/III minima for properly equipped runways and aircraft. GBAS can support approach minima at airports with fewer restrictions to surface movement and offers potential for curved precision approaches. GBAS may also support high-integrity surface movement requirements.

    — Bill Thompson, GPS World aviation editor

    LightSquared-Sprint Contract Terminated

    Business Case for GPS Threat Gone Away

    The principal business prop under the LightSquared plan for ancillary terrestrial component (ATC) broadcast of a powerful signal that would have disrupted GPS operations dropped out from under the company on March 16, as wireless carrier Sprint terminated its $9 billion agreement with LightSquared. LightSquared had several such partnership agreements, but the Sprint deal was the largest, and in many eyes the driver of the aggressive plan. With it gone, LightSquared’s other deals will likely dissipate — and the current threat, at least, to GPS industry and users should effectively go away.

    Sprint has apparently concluded that LightSquared has no prospect of reversing the revocation of its conditional waiver last month by the Federal Communications Commission, as a result of extensive testing conducted by the company, various government agencies, and the GPS industry. Earlier, Sprint had twice extended its tentative agreement with LightSquared as the tests took place over the last year, but reached the end of its road March 16 — which is also the last day the FCC is accepting public comments on its decision to revoke the waiver.

    An official LightSquared statement said termination of the Sprint agreement was “in the best business interests of both companies, and was not unexpected given the regulatory delays.” Sprint will return $65 million in prepayments that LightSquared made to Sprint.

    Some analysts have predicted that LightSquared may be forced to sell off its assets by the end of the year. Among these assets are the spectrum licenses for the lower LightSquared band (1526–1536 MHz), the so-called Low 10, and the higher band (1545-1555 MHz), known as the Upper 10, adjacent to GPS L1. These bands have a history of trading hands as their owners go into bankruptcy or otherwise out of business.

    The next touchpoint of concern for the GPS community is the outcome or perhaps various outcomes of the FCC workshop on spectrum efficiency and receivers that took place March 12–13. The workshop was convened to discuss the characteristics of receivers and how their performance can affect the efficient use of spectrum and opportunities for the creation of new services, according to the FCC.

  • UrsaNav Testing Wide-Area Timing Alternative

    As a result of a Cooperative Research and Development Agreement (CRADA) between the U.S. Coast Guard and UrsaNav, Inc., on-air tests are being conducted from the former Loran Support Unit site in New Jersey.

    One of the CRADA’s goals is to research, evaluate, and document a wireless technical approach as an alternative to GPS for providing precise time. The ability to obtain precise time to at least one microsecond is necessary for the proper operation and functioning of many critical industries and systems. Examples include telecommunications networks, banking and finance, energy and power delivery, emergency services, transportation systems, and military and homeland security systems.

    Additional on-air tests are planned at various sites throughout the United States. Broadcasts will test several different frequencies, waveforms, and modulation techniques using evolutionary, state-of-the-art technology. Reception of these broadcasts are planned at both on-shore and off-shore locations, and will include advanced LF data delivery techniques. The results of these trials will be presented at national and international conferences. Any party interested in any part of the trial, or interested in doing their own measurements, are invited to contact us.

    UrsaNav provides advanced solutions for Low Frequency Alternative Positioning, Navigation, Timing, and Data, including high-performance eLoran Timing Receivers. The company has partnered with precise-time synchronization company Symmetricom and Nautel, supplier of high-power RF transmitters. According to UrsaNav, this “alliance of expertise” provides the foundation technology for a wide-area, terrestrial-based alternative to satellite systems such as GPS, GLONASS, and Galileo.