If you have critical infrastructure that demands the highest level of protection, you’re a candidate for an STL-based system.

Satellite Time and Location, or STL, is a system that augments GNSS or serves as a backup to GNSS in critical systems. By using a globally available system that is not susceptible to the same vulnerabilities as GNSS, it’s possible to strengthen your critical infrastructure and reduce the risk of complete system failures to due to intentional or unintentional interruptions of GNSS service.

The higher transmission power and encrypted signals from STL provide the highest level of protection available today – and it is much less susceptible to typical GNSS threats.

STL: Adding Resilience & Trust to GNSS

  • 1000x stronger signal than GNSS
  • Deep Indoor Penetration
  • Encrypted signal resists spoofing
  • Global coverage with 66 satellites

What is STL?

STL is a satellite-based GNSS augmentation system. Originating from the Iridium® constellation of 66 low-earth-orbiting satellites, STL is 1,000 times stronger than GNSS, reaching deep into buildings and preventing GNSS jamming without the aid of local infrastructure. STL signals are further protected by cryptographic security features that are much more difficult to misdirect or “spoof.”

In a world where we have come to expect GNSS to be always operational, STL provides the safest, strongest, most dependable backup to our GNSS infrastructure today.

Advantages over GNSS

GNSS (Global Navigation Satellite Systems) like GNSS, Galileo, and GLONASS are typically associated position and navigation. However, the signal transmitted by these systems is, in reality, a very precise time code that receivers use to determine position. This time code can also be used to synchronize networks anywhere in the world to within billionths of a second.

Because of this, GNSS has become deeply woven into the fabric of today’s technology and is used across many industries. For example, the transportation industry, communication networks, financial systems, power grids, and others rely upon GNSS to synchronize their networks.

Operators of commercial and public applications that are considered “critical” rely on GNSS as their exclusive source for their timing needs. For these operators and their customers, critical means nothing less than “too important to fail.”

STL in a nutshell

  • Broadcast on the Iridium satellites
  • >30 dB stronger than GNSS
  • Higher jamming and interference resistance
  • Operates indoors
  • Encrypted signal
  • Inherently anti-spoof
  • Subscription based service
  • Available for civilian use

Understanding GNSS vulnerabilities

Our heavy reliance on GNSS for critical applications raises questions and concerns about vulnerabilities. There are potential disruptors, whether unintentional or intentional, such as jamming and spoofing. You must ask yourself: How robust is my application, and what is my backup plan? Consider these facts:

Understanding GNSS vulnerabilities

  • 12,500 miles is the altitude of the medium Earth orbit used by GNSS satellites. By the time the signal reaches Earth, it is so weak that it blends in with the naturally occurring background noise.
  • Four GNSS satellites are required to provide a position fix, including time. In urban and other environments with a limited view of the sky, it may be difficult to maintain a lock on the minimum number of satellites.
  • In 2013, a man was fined $31,000 for the use of a GNSS jamming device that was routinely interfering with the aviation systems at the Newark Airport. It took more than two years to identify the jammer. Although illegal, jammers are easily available for purchase and have already demonstrated their significant impact on critical systems. http://www.gpsgps.gov/spectrum/jamming/
  • Dr. Todd E. Humphreys, a noted academic expert in GNSS spoofing, has successfully demonstrated the ability to spoof the GNSS systems of devices, ranging from commercial UAVs to multimillion dollar luxury yachts, using commercial off the shelf components. In addition, commercial GNSS signals are unencrypted and the software code needed to simulate these signals is available on public forums.

GNSS and STL – A system comparison

Global coverage Global coverage
66 Iridium satellites 24 satellites
500-mile orbit (LEO) 12,500-mile altitude
100-minute orbit 12-hour orbit
1000x stronger than GNSS 25x farther away

What are the benefits of STL?

  • Time sync – STL augments GNSS with an independent stronger signal. Plus, it is anti-spoof with subscriber authentication of an encrypted signal
  • Deep indoor penetration – No outdoor installation or cabling is required, and it is 1000x stronger than GNSS
  • Trusted location – STL is security-based on geo-location
  • No roof antennas – no landlord permission needed, no zoning restrictions, no building hazards such as asbestos, no outdoor equipment maintenance, and no $10,000 to $1,000/month installation fees.

STL in action: use cases

  1. New York Stock Exchange
    In January 2017, STL was demonstrated indoors at the ATIS Time and Money Event. It was on Wall Street – one of the world’s most difficult urban canyons for GNSS reception. And, in a 7th-floor interior room with a weak signal. Result: STL signal was received and locked to UTC time (with Spectracom’s SecureSync). It took less than 30 minutes to converge.
  2. STL for telecom and European financial compliance
    The telecom industry is required to maintain a network synchronization accuracy of 1.5 microseconds (Source: ITU Recommendation G.8271/Y.1366 (07/16)). In Europe, 100 microseconds is the time synchronization accuracy requirement by MiFID II for the financial market. GNSS speeds are noncompliant with these requirements. STL, however, is.
  3. STL for enhanced geo-location security.
    A key advantage of STL is its ability to provide time and position fixes under conditions where GNSS is not available due to occlusions, spoofing or other issues. Another key advantage is the receiver’s ability to confirm that it is not being spoofed. The proprietary STL signal format includes cryptographically secure features that unambiguously demonstrate that a signal burst was received directly from a satellite – rather than being synthesized or delayed and rebroadcast by an attacker.

    These cryptographic features also allow the receiver to prove its current location to a third party. This location-based authentication provides an independent confirmation of the identity of a remote system or user.

In Conclusion

Recent studies and warnings published by DHS have warned of the vulnerabilities in our critical infrastructure due to the dependence on a single system (GNSS) that is susceptible to interference and jamming/spoofing attacks. STL can be used to augment GNSS or as a backup to GNSS. By utilizing a globally available system that is not susceptible to the same vulnerabilities as GNSS, it is possible to both strengthen our critical infrastructure while reducing the risk of complete system failures due to intentional or unintentional interruptions of GNSS service. The higher transmission power and encrypted signals from STL provide a level of protection that is less susceptible to typical GNSS threats.

For More Information:

Lisa Perdue
Lisa Perdue

Lisa Perdue is a world-leading expert in testing critical GPS and GNSS systems. She has trained hundreds of engineers and technicians who are responsible for high-reliability positioning, navigation and timing (PNT) applications. She took a lead role in the development of the first GNSS Vulnerability Test System and speaks widely on the topic at many industry conferences. Lisa Perdue is currently the simulation product line director at Orolia, directing the organization’s GNSS simulation activities and contributing to its entire portfolio of resilient PNT solutions. She has more than 15 years of navigation and RF systems experience, which includes 10 years of service with the U.S. Navy, where she was a certified master training specialist.

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