Session A1: Navigation Security and Authentication

A Galileo PRS/HAS Compatible CRPA for Both PNT-Resilient and Accurate Positioning
Lorena Tortajada Ropero, Rubén Morales Ferré, Javier Garcia-Madrid Velázquez, Raquel Montero Montero, Beatriz Bengoa Robles, and Antonio González Novell, Satellite Navigation Department, INDRA Space
Location: Holiday 1 (Second Floor)
Date/Time: Wednesday, Sep. 10, 8:35 a.m.

Abstract— Global Navigation Satellite Systems provides service to a wide variety of sectors, from transportation (e.g., vehicles navigation, asset tracking, etc.) to timing and synchronization (e.g., telecommunications, economic transactions, etc.). Some of these are safety critical applications, requiring high accuracy, integrity, robustness, and continuity of the service. In this sense, Controlled Reception Pattern Antenna (CRPA) has emerged as a key technology in enhancing the robustness and resilience of the GNSS service. The main objective of CRPA systems is to mitigate the impact of unintentional interferences (i.e., adjacent channel/co-channel interferences, caused by the space weather, etc.) and intentional attacks (i.e., jamming, spoofing, etc.) by adapting the reception pattern of the antenna in a dynamic way. In addition, most CRPA systems combine embedded signal processing units for filtering the received GNSS transmissions and for delivering interference-free signals to the GNSS receiver.
This paper presents a CRPA system with advanced interference detection, localization, and mitigation capabilities for civil and non-civil applications, including safety-of-life applications. This CRPA system is one of the first antennas in the market handling the Galileo Public Regulated Service (PRS) and Galileo High Accuracy Service (HAS) along with GPS M-Codes, besides the GPS and Galileo legacy operational frequency bands.
GNSS, including HAS is widely used in road applications across multiple domains. These applications can be categorized as safety-related, where precise positioning information supports safety-critical operations (e.g., connected and automated vehicles) or enhances emergency assistance services. With the advent of automated driving, automakers are increasingly dependent on precise and high-performance positioning technologies. In this sense, the CRPA plays a crucial role ensuring the reliability of positioning.
The CRPA is composed with an advanced digital processing unit in order to digitally apply signal processing algorithms for detecting, characterizing, localizing in 2D and mitigating different types of interferences. More in detail, the CRPA is able to detect interferences in the three domains: time, frequency and space. In concordance, the CRPA implements three signal processing algorithms for covering the before-mentioned domains. Therefore, the CRPA offers versatile protection against interference and jamming, making it one of the most robust solutions for ensuring GNSS reliability.
The time-based algorithm is specifically designed for mitigating intermittent and repetitive pulsed signals such as interferences coming from frequency-adjacent systems (i.e., TACAN/DME) which transmits periodically a high amount of power in a very limited time period. The frequency-based algorithm is specifically designed for mitigating narrowband signals, such as continuous wave signals (i.e., AM/FM tones, etc.). The spatial-based algorithm is designed for mitigating the wideband interferences (i.e., chirp, noise-like signal, etc.) by adapting the receiving radiation pattern for blocking the Direction of Arrival (DoA) of the estimated interferences by means of Nullforming processing, while improving the desired GNSS satellite signals. The CRPA dynamically selects, combines, and adjusts the interference mitigation techniques to ensure maximum protection in real-time. For doing that, a sophisticated algorithm is designed in order to both prioritize and optimize resource allocation, ensuring the best trade-off between performance, computational efficiency, and threat severity.
The RF output signal is compatible with any Commercial off-the-shelf (COTS) GNSS receiver. Thus, the presented CRPA operation is totally transparent from the receiver point of view. In addition, the proposed CRPA system incorporates a novel adaptive frequency response correction mechanism. This feature continuously monitors the RF signal characteristics and applies corrections to maintain a stable frequency response. By compensating for variations in the RF chain, the system minimizes signal distortions that could affect the receiver’s ability to process GNSS signals accurately. A comparison before and after applying the correction mechanism shows a significant improvement in terms of GNSS signal quality.
For controlling and commanding the CRPA, a Graphical User Interface (GUI) has been developed. This application displays information about the CRPA operation, including hardware information (i.e., temperature, status, etc.) as well as information related to detected and mitigated interferences (i.e., interference type, affected bandwidth, power of the interference, pulse duration and repetition, etc. The CRPA GUI provides receiver independence, allowing for the assessment of Situational Awareness in a specific area. This means that through the graphical interface, one can visualize and analyze information regarding the GNSS environment as well as threats existence. This enhances the resilience and accuracy of the system in complex and interference-prone scenarios.