GNSS Anti-Jam & Anti-Spoof Antenna Technology for Multimodal Transportation 

Project Description:  One strategy for toughening receivers is direction-of-arrival sensing. The technique relies on a multi-element GNSS antenna or the equivalent. Such techniques are uniquely well suited to the detection and mitigation of jamming and spoofing attacks on land, air, and sea vehicles. We have examined and developed several multi-element technologies such as controlled reception pattern antennas (CRPA) based on commercial off-the-shelf (COTS) components and dual polarization antennas (DPA).  CRPA and DPA enable spoofing detection as they are sensitive to the direction of arrival (DOA) of each incoming signal. Spoofing can be detected if the indicated DOAs do not align with anticipated DOA or if the DOAs of all satellite signals come from one direction as may be expected with a single-antenna spoofer. Additionally, CRPAs and DPAs can produce nulls, mitigating the effects of interference.  We propose two developments with the goal of transferring these capabilities to manufacturers for use in civil applications. 

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1.  CRPA development has not been widely explored for civilian transportation due to export restrictions on the number of antenna elements and their capabilities. However, some restrictions have recently been relaxed. Additionally, the technology to have large arrays of antennas is widely available (e.g., used in 5G technology which have about 1000 elements) and not cost prohibitive (Starlink base stations cost $599). We have developed small arrays (4 elements or less) compliant with current restrictions. We will explore arrays that meet current restrictions and those that do not, the latter to explore the possible benefits to R-PNT in advanced transportation systems of further relaxation of restrictions.  

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2.  DPA for spoofer detection is a newer technology that utilizes an antenna that can receive both left-hand and right-hand circularly polarized (LHCP, RHCP) signals to induce DOA sensitivity. This concept came out of a 2016 Stanford Ph.D. thesis. We later demonstrated that it can be built using COTS parts. We flight tested this concept in 2019. Two implementations were tested – one based on COTS GNSS chipset where the estimation of DOA effects took several seconds due to a serial search process needed to find the incoming phase offset between the LHCP and RHCP. The other used custom software receiver processing to directly solve for the phase ambiguity. One challenge with this concept is building a system that can make continuous DOA calculations using COTS hardware. A second challenge is to develop techniques for handling DOA errors and measurement ambiguity (e.g., 180-degree ambiguity).   

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US DOT Priorities:  This research project directly targets the US DOT’s research priority area of Reducing Transportation Cybersecurity Risks. We will be investigating novel GNSS receiver signal processing and antenna solutions to help ensure resilience to jamming and spoofing.  We will develop, implement, and test advanced GNSS DOA-sensitive antenna architectures and the associated signal processing techniques that significantly surpass existing methods and algorithms for jamming resistance and spoofing detection and exclusion. The results would ultimately be deployable in the individual vehicles that exist in the greater transportation ecosystem. 

Outputs:  In this work, we will examine how to build larger GNSS arrays with COTS components that are suitable for ground, maritime and rail transport applications. The challenges include being able to support precise GNSS navigation techniques such as Precise Point Positioning (PPP) needed for autonomous driving and being able to do it with reasonable hardware and processing requirements. In this research project, we propose to:  

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• Evaluate the feasibility and cost of mounting such mitigation systems on a vehicle.  

• Propose techniques to enhance resilience in ways that yield acceptably low size, weight, and power budgets and satisfy sensor placement constraints.  

• Perform live-signal tests, for example, at a U.S. Army PNTAX exercise at White Sands Missile Range or at a similar DoD, DHS exercise.  

• Consider new GNSS PNT spoofing and jamming mitigations specific to port and CAV operations. 

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We expect interest in this research from GNSS antenna and receiver manufacturers and will actively encourage contributions of the CARNATIONS External Advisory Board.  

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Outcomes/Impacts:  This project seeks to make important strides toward the realization of commercial GNSS multi-element antenna technologies that address the challenging radio-frequency interference and in a form factor that is suitable in many transportation applications.  The project results will be shared with the DOT, GNSS researchers, industry, and standardization bodies.  

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Final Research Report:  (Upon completion of the project we will a provide link to the final report.)