northeastern university seal
EXPLORE NORTHEASTERN

Closas Receives NSF CAREER Award

ECE Assistant Professor Pau Closas received an NSF CAREER award for "Secure and ubiquitous position, navigation and timing."


Bringing GPS Indoors

For the past decade, Electrical and Computer Engineering Assistant Professor Pau Closas has focused on a unique technological challenge in navigation: increasing the sensitivity and accuracy of Global Navigation Satellite System (GNSS) receivers, a key step in overcoming limitations of the GNSS—the umbrella system that encompasses the Global Positioning System (GPS).

Closas’s work recently earned him the prestigious National Science Foundation CAREER Award, a five-year, $500,000 grant for research and education and outreach programs. The award will help Closas—who joined Northeastern in 2017—and his team address some of the most common GNSS receiver challenges, including indoor usage, signal spoofing, and disruption by malicious actors.

Based on his research, Closas proposes an architecture for GNSS receivers that will increase accuracy and sensitivity on a higher range of scenarios. “The current receiver architecture uses two steps,” he explains. “Satellites send signals and the receiver processes each satellite’s signals independently, extracting information to estimate position and then combining them all. We propose moving to a one-step process by optimally combining all these signals directly to determine position more accurately.”

One of the groundbreaking applications of the new architecture, according to Closas, is “to bring GPS indoors,” which would provide the ability to navigate with a phone and GPS receiver inside a building. More robust GNSS receivers can also address current navigation limitations with self-driving cars and thwart jamming devices that, for example, have the potential to cause catastrophic damage to the power grid, which is synchronized with GNSS timing. “We can combat these effects with this technology,” he says.

As principal investigator for the research project, Closas oversees a four-person team of doctoral students that he plans to grow. Because the educational component of the NSF CAREER award is tightly linked to an Open Source project that Closas has worked on for several years, researchers both inside and outside of Northeastern will benefit. “We’ll incorporate our findings into the Open Source project implementing GNSS receivers,” he says, “so the knowledge we generate is public and available to the scientific community. Everyone can benefit.”


Abstract Source: NSF

The long-term objective of this project is to enable secure position, navigation and timing (PNT) anywhere, a longstanding goal since ancient times. Currently, the most pervasive PNT technology is Global Navigation Satellite Systems (GNSS). However, GNSS exhibits major vulnerabilities and limitations under certain conditions such as indoor navigation, malicious attacks like jamming or spoofing, and other GNSS-denied scenarios. This five-year career-development plan is a comprehensive research, education, and outreach program that will address GNSS limitations and form the next generation of PNT engineers. The combination of both elements will unlock the potential of secure and precise PNT using GNSS technology for indoor, as well as outdoor use. The objectives of the proposed research and education plan are: 1) to forge a novel, overarching signal processing paradigm to design advanced GNSS receivers. The PI will adopt direct-positioning to yield unprecedented ultra-high-sensitivity performance, enabling GNSS indoors; 2) to further reinforce of the theory of direct-positioning by incorporating security guarantees and mechanisms by using robust statistics; and 3) to implement an ambitious educational plan that includes multifaceted activities involving the use of the open source GNSS software-defined radio (GNSS-SDR) project. In turn, the GNSS-SDR will be deeply integrated with the research endeavors as a testbed, which naturally intertwines both research and education aspects of this project following the PI's ongoing efforts. The success of the proposed research will impact many applications where PNT is provided by GNSS, for which current limitations prevent faster adoption. This includes critical infrastructures, such as the power grid, first-responder squads, unmanned and autonomous vehicles, intelligent transportation systems, precision surveying, agriculture, or mass-market applications involving hand-held devices.

The project addresses a fundamental question in secure and ubiquitous PNT: what are the real limits of GNSS-denied scenarios. The research deepens around the direct-positioning paradigm, which is recognized by the GNSS community as a breakthrough in the design and understanding of GNSS technology. The main intuition is that synchronization parameters of all satellites are intimately related among them through the receiver position and velocity. The fact that all those signals are received at the same location and time instant is a strong constraint that is not exploited in current PNT schemes. In contrast, direct position estimation (DPE) jointly processes those signals, increasing its sensitivity and robustness to common propagation challenges such as weak signal, amplitude fading, multipath, jamming, spoofing, or ionospheric scintillation, therefore yielding to superior resilience in currently GNSS-denied environments. The research goals are structured in three thrusts: 1) to establish a DPE framework that allows for ultra-high-sensitivity receivers to operate in extreme environments, such as indoors. Tasks include derivation of the fundamental estimation bounds as well as investigation of the signal processing and sensor fusion methods that enable to efficiently attain those limits. The project will investigate the integration of DPE with real-time kinematics, extending the availability of high-precision PNT; 2) to secure GNSS receivers against malicious attacks, and ionospheric scintillation. DPE schemes will be leveraged to combat such interferences in combination with robust statistics, machine learning, and Bayesian inference tools. As a result, a transformative, unified framework will be conceived for sub-decimetric precision GNSS receivers that are both secure and can operate in denied scenarios but are not possible using current technology; and 3) to implement and validate the developed techniques on an end-to-end GNSS-SDR receiver, around which a research and educational plan is conceived to boost and consolidate the area of secure and ubiquitous PNT.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Related Faculty: Pau Closas

Related Departments:Electrical & Computer Engineering