This article originally appeared on Fierce Wireless Tech on May 15, 2023.

The value – and vulnerabilities – of GPS/GNSS timing synchronization for today’s critical infrastructure 

For over thirty years, the Global Positioning System (GPS) has become integral to the operations of almost every commercial sector. It is essentially a global utility, one that provides precise positioning, navigation, and timing (PNT) information anywhere in the world. The timing synchronization enabled by GPS powers millions of critical infrastructure assets such as telecom networks, financial systems, and power grids, all which rely on a steady stream of precise timing and location information.

It’s mainly by looking at life without GPS that we understand its true value: a June 2019 report sponsored by the National Institute of Standards and Technology estimated that if GPS were lost, the economic toll would amount to $1 billion per day.

That isn’t necessarily a hypothetical risk, because despite its worldwide usage, GPS has inherent vulnerabilities and is subject to serious threats. For example, the GPS signal isn’t that strong — it is susceptible to signal degradation by buildings, tunnels, tree canopies, and other obstructions.

Unintentional events such as a system outage are rare. The biggest threats are from bad actors who deliberately attack GPS to disrupt or manipulate the signal.

presidential executive order from 2020 said that “[t]he national and economic security of the United States depends on the reliable and efficient functioning of critical infrastructure,” adding that GPS has become “a largely invisible utility for technology and infrastructure, including the electrical power grid, communications infrastructure and mobile devices, all modes of transportation, precision agriculture, weather forecasting, and emergency response.” The executive order directed critical infrastructure providers to ensure the resilience of their technology so that any disruptions to GPS would have minimal effects on their operations.

This all points out just how important GPS is to our economy and national security and why there needs to be a contingency capability to back it up. Alternative forms of PNT, such as STL from Satelles, can ensure the survivability and resilience of critical infrastructure, including 5G wireless networks.

STL as a complement – not replacement – for timing synchronization in 5G wireless networks using GPS/GNSS

Wireless communications networks rely on accurate timing and synchronization from GPS and other Global Navigation Satellite Systems (GNSS) signals to function properly. Compared to 4G, 5G networks require more precise timing and have five to ten times as many locations. The majority of these 5G network sites are indoors where GNSS is challenged. These include enterprise and residential locations comprising malls, hospitals, hotels, large venues, and high-rise office and apartment buildings.

The inability to receive GNSS inside buildings — as well as the loss of GNSS via disruption, manipulation, or equipment failure — has been known to disable critical equipment, including macrocells and small cells.

Engineering and operations personnel from wireless carriers know all too well how widespread the effects on their networks can be when things can go wrong with timing synchronization.

GPS/GNSS Cabling and Antenna Issues:

  • Fighting to obtain landlord permissions for roof rights to install a GNSS antenna — and then obtaining it after great effort only to have to pay exorbitant one-time or ongoing fees to keep the antenna on the roof. Dealing with time-intensive and unpredictable roof-rights permissions process and installation scheduling, often at multiple sites, can delay 5G roll-outs.
  • Dealing with the hassle and expense of coring through multiple floors of a high-rise building to gain access to the roof to run the cabling for a GNSS antenna.

GPS/GNSS Signal Issues:

  • Being frustrated by an inability to receive accurate timing to indoor nodes, even with an outdoor antenna.
  • Grappling with signal multipath issues in urban areas.
  • Enduring repeat alarms and initiating multiple truck rolls because of GPS bouncing.

Unique features of STL Timing Synchronization technology to complement GPS

“Our STL solution is […] ideal for providing accurate, reliable timing where GNSS can’t reach,” said Christina Riley, Vice President and General Manager of Commercial Enterprise Solutions at Satelles, in a company announcement with Adtran, Inc. In settings where it is possible to receive GNSS signals, but where there are concerns for GNSS disruption, STL complements GNSS with additional PNT services to improve resiliency.

Having a signal that passes through structures is especially important for buildings where securing roof rights, obtaining landlord permissions, or complying with local zoning restrictions are a challenge. An indoor solution for assured timing lowers cost and reduces the risks related to installation and maintenance of outdoor antennas.

“Ultimately, we don’t think of it as replacing GPS user equipment,” said Dr. Michael O’Connor, CEO of Satelles, in an interview with GPS World. “Rather, where a user has a need for PNT, they’re opting for this GNSS + STL solution because they have an indoor need, such as a data center, or they have a need for resilience in the case of a stock exchange.”

STL is unique in that its signals are powerful, extremely secure, and available worldwide. “We have focused on three unique aspects in the areas where GPS could use complementary service,” O’Connor explained. “First […] we aim to provide an independent source of position, navigation, and timing (PNT).”

“Second, we focused the high-power aspect of STL to enable us to reach indoors and other places where GPS does not reach,” said O’Connor. Due to the proximity of LEO satellites and a high-power satellite signal, STL broadcasts are stronger than GPS, allowing them to penetrate GPS-challenged environments where signals are obstructed or degraded, including indoors and underground.

O’Connor continues, “Third, we use modern cryptographic techniques to ensure the security and resilience of the system, specifically to intentional misdirection attacks. If you can ensure that the signal is coming from the satellite and not from a third party, you can have a more secure and resilient solution.”

STL is a proven and secure alternative to GPS/GNSS Timing Synchronization

STL is neither an experimental technology nor a proof-of-concept. It has been commercially available since 2016, and STL-capable receivers are currently being used worldwide to provide resilient, high-accuracy UTC timing as a primary source of time or backup to GNSS and are doing so indoors and in other challenging settings. STL is a LEO PNT service provided via the Iridium satellite constellation.

Telecom operators and other companies use STL today as a primary timing source. Critical infrastructure owners and operators also rely on STL as an essential contingency capability to protect the operations of PNT-dependent systems and ensure survivability and resilience.

Government authorities in the U.S. – including the National Institute of Standards and Technology (NIST), the Department of Homeland Security (DHS), and Department of Transportation (DOT) – as well as the European Commission’s Directorate-General for Defence Industry and Space (DEFIS) have subjected STL to rigorous technology evaluations.

Satelles has a multi-year track record of providing reliable 24/7 timing synchronization services to customers within wireless operators, banks, major stock exchanges, data centers, and other industries across the globe.

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