Tech Neutral, Diverse Approach Critical for Global GNSS Backup

Dr. Michael O’Connor, CEO and Christina Riley, Vice President and General Manager, Commercial Business, Satelles highlight the economic impact of resilient PNT on key industry sectors and the role of national government to enable a dynamic geospatial infrastructure ecosystem.

A greater than ever number of consumer products, commercial services, and industrial applications are reliant on geolocation provided by GPS/GNSS. Apart from that there are incredibly important positioning and timing needs of national critical infrastructure that rely solely on GPS/GNSS — including telecommunications networks, power grids, transportation systems, and data centers.

The widespread use of GNSS-enabled devices has brought in a range of applications that deliver safety, security, and consumer services. Improved GNSS services have made devices cheaper, smaller, and faster resulting in providing accuracy at levels that has made highly detailed mapping and navigation capabilities possible, which are used in industries such as 5G wireless networks and financial services just to name two out of the many. Other industries are realizing the power of location intelligence (LI) and slowly adopting this technology, which is why more knowledge of the integrity/reliability of GNSS is required to develop new applications in future.

Although GNSS devices remain vulnerable to deliberate attacks of manipulation, interference, and disruptions caused by external factors.

But this vulnerability does not just result in an exposure to catastrophes, but also makes critical infrastructure systems that rely on GPS vulnerable.

For example, cell sites are at grave risk for outages because a time-division duplex (TDD) timing error exceeding 1.5 microseconds of UTC will not only cause a shutdown of a single cell site but also impact the surrounding 10 to 15 sites, thereby cascading into a regional outage. This underscores just how important GNSS is for the economy and national security and why there needs to be a contingency capability to protect it.

What is Resilient PNT?

Resilient PNT is not a technology or service; rather a combination of two things:

1. Resilient PNT is the state or condition of protecting the forms and sources of PNT for any PNT-dependent application against disruption or manipulation.

2. It is the practice of ensuring that multiple alternative forms of PNT matching the performance specifications and operational characteristics of PNT-dependent applications are in place and that they are also protected.

ALSO READ: Positioning, Navigation and Timing (PNT) is driving World Economy

Dr. Michael O’Connor, CEO of Satelles, states, “The concept is also context- and application-specific because achieving a state of resilient PNT for a user, a company, a critical infrastructure sector, or a nation are all quite different things. In other words, resilient PNT takes on different meanings depending on the scale or scope of the application or system that is being protected and backed up.”

Alternative technologies that can complement GPS/GNSS

There are several PNT technologies that can complement GPS/GNSS, which generally fall into multiple categories such as network time transfer services, terrestrial broadcasts, signals of opportunity, and Low Earth Orbit (LEO) satellites. The technologies in each of these categories have different characteristics and different levels of readiness. One thing for certain is that there is no single, silver bullet solution that will meet the needs of all industries.

Christina Riley, Vice President and General Manager, Commercial Business, Satelles states, “In the LEO PNT category, Satelles offers Satellite Time and Location (STL), a solution that is engineered to provide not only a complementary form of PNT but also a primary source of time in locations where a reliable GPS signal is unavailable, such as interior  5G sites for wireless networks.”

The satellites that provide STL are 25 times closer to the Earth’s surface and deliver signals 1,000 times stronger than GPS. This makes STL extremely difficult to disrupt or degrade compared to GNSS, and it allows signals to serve users in hard-to-reach places, such as indoors, underground, and in urban canyons. The polar satellite orbit provides a strong signal at the poles (where GPS is weakest).

She explains that one key advantage of LEO satellites for PNT is that the solution is scalable and ubiquitous— the 66 satellites cover Earth without the need for additional radio transmitters or other dedicated equipment. This makes an LEO solution highly suitable for applications that require a wide-area, nationwide, or even worldwide service, such as wireless communications networks, mobile payment services, and the power grid.

Satellites are also vulnerable to space weather, but those at the lower orbital altitude — LEO satellites — are well protected from space disturbances (like solar storms) and are far less susceptible to the harmful effects of internal charging and surface charging that can cause permanent damage to the electronic components of space vehicles such as GPS satellites that operate in the MEO orbit.

LEO satellites are better shielded from these phenomena because they orbit below the Earth’s magnetosphere and the inner Van Allen Belt (planetary radiation belt). The satellites that broadcast STL orbit at a higher altitude than many other LEO satellites, which means that even within the LEO region they are less vulnerable to orbital drag potentially caused by solar storms.

ALSO READ: Resilient PNT for a Self-Reliant India

Local terrestrial beacons too have an important role in GPS augmentation and backup for certain critical infrastructure sectors. While these systems don’t cover a wide area and can face spectrum licensing issues, they can provide exceptional accuracy and good indoor penetration, making them well suited for emergency first responders.

Network-based solutions are another technological innovation that plays a focal role in certain sectors, particularly where users have a precision timing need for the networks that serve their locations.

Role of national government to enable a dynamic geospatial infrastructure ecosystem

Implement diverse technologies for true resilience — The US government has repeatedly stated in reports from the Department of Homeland Security (DHS), Department of Transportation (DOT), and other agencies that no single product, service, solution, or technology can meet the requirements of all PNT-dependent applications.

A report published by DHS in 2020 opines: “… diversity of capabilities in the national PNT ecosystem is a strength, not a weakness.” DOT reached a similar conclusion in its technology demonstration report, stating that “none of the systems can universally back up the positioning and navigations capabilities provided by GPS and its augmentations.” For these reasons, the government should urge industry to implement multiple technologies instead of endorsing or investing in a single solution as a contingency capability to back up GPS.

Competition drives innovation – Like the companies that make up the Open PNT Industry Alliance (of which Satelles is a member), Satelles agrees with what DHS said in 2020 with regard to the US Government potentially selecting just one backup for GPS: “… the government would have to consider the repercussions of such a system in the marketplace” because “[a] free government system would negatively impact commercially available PNT systems by directly competing with them.”

The last thing anyone needs is a government monopoly that stifles open market competition and brings to a halt the incredible pace of innovation that are taking place right now in the PNT market.

Government should adopt multiple PNT sources– Satelles’ believes that a truly resilient and globally available GPS/GNSS backup capability is only possible with a technology-neutral approach that encourages diversity.

Satelles agrees with DHS that “the Federal Government should encourage adoption of multiple PNT sources [by] critical infrastructure owners and operators [and] focus on facilitating the availability and adoption of PNT sources in the open market.”

The same is true in other countries, and therefore national governments should urge industry to implement multiple technologies instead of endorsing or investing in a single solution as a contingency capability to back up GPS/GNSS.

Recent reports published by the U.S. National Institute of Standards and Technology (NIST), the government entity responsible for maintaining the national standards for time and frequency in the United States in coordination with the United States Naval Observatory, confirm Satellite Time and Location (STL) as a source of resilient time and describe its benefit as an element of the agency’s recommendation for a resilient timing architecture.

Tech Neutral, Diverse Approach Critical for Global GNSS Backup