Detecting and Measuring Global GNSS Signal Interference via Space-Based ADS-B Surveillance

In this paper, we develop a novel method to detect Global Navigation Satellite Systems (GNSS) spoofing for an Automatic Dependent Surveillance-Broadcast (ADS-B) equipped aircraft. The Federal Aviation Administration (FAA) has mandated [18] all civil aircraft to be ADS-B Out equipped by January 1, 2020. The ADS-B Out broadcast sent to Air Traffic Control (ATC) consists of the aircraft's position, velocity, and other aircraft-specific information, all of which being unencrypted, poses a serious integrity threat. With readily available ADS-B trackers [19], [20], a spoofer can accurately track an aircraft to generate a spoofed trajectory that can go undetected [11]. We propose a novel method to modulate the ADS-B Out position broadcast such that a spoofed trajectory generated using the modulated ADS-B will be detectable by comparing Inertial Navigation System (INS) positions against those obtained using the spoofed GNSS signal. The amplitude of ADS-B modulation is selected to exceed the nominal INS error covariance so that spoofing is observable. In this work, we analytically quantify the magnitude of ADS-B modulation that will be sufficient for spoofing detection. During scenarios of GNSS signal jamming and spoofing, reauthentication of a reacquired GNSS signal is necessary to maintain integrity. During a GNSS outage, given enough time, the INS solution drift will grow large enough such that the spoofed GNSS solution might be within the INS error covariance envelope and go undetected. For GNSS outage scenarios we propose continuous modulation of ADS-B position and analytically quantify the magnitude such that spoofing of the GNSS signal is detectable after signal is re-acquired.

Air traffic control nowadays mainly relies on radar based surveillance system and with the growth of air traffic, the problems of air transportation system is approaching its limit. The increase in the task of scheduling flights results in higher overall operation cost and pose higher rate of flight safety hazards. Thus, an upgrade from conventional air traffic management systems to the Next Generation Air Transportation (NextGen) System is required. The Automatic Dependent Surveillance Broadcast (ADS-B) modem is the key component of NextGen, which uses Global Navigation Satellite System (GNSS) to provide better accuracy of aircraft position. ADS-B continuously broadcasts information on altitude, position, identity, velocity, and other aircraft information to generate best picture for air traffic management. In this paper, the ADS-B modulator and demodulator have been developed using high-level RVC-CAL dataflow actor language, and automatically synthesized to C and Verilog/VHDL codes for hardware and software implementations. Results show that the performance of the proposed designs at high-level exceeds the minimum throughput requirement specified in the ADS-B standard by a factor of more than three.

The number of Small Unmanned Aircraft Systems (SUAS) has greatly increased in recent years. And it is expected that this number will continue increasing in the future. The SUAS may be operated in proximity of aerial vehicles (including aircraft) and it may be necessary to detect them electronically. One possibility is to equip SUAS with Automatic Dependent Surveillance – Broadcast (ADS-B) surveillance system operating on 1090 MHz frequency. The purpose of this study is to investigate the impact of SUAS ADS-B 1090 transmissions on the reception of an aircraft ADS-B Extended Squitter by an ADS-B ground station. The systems being considered operate at low altitudes, typically under 500 ft above ground level (AGL). We found that high number of SUAS equipped with ADS-B flying close to ground ADS-B sensors can have significant impact on the operational range up to 40%.

The localization of multiple interference sources in Global Navigation Satellite Systems (GNSS) can be achieved using carrier-to-noise ratio (C/N0) information provided by GNSS receivers, such as those embedded in smartphones. However, in increasingly prevalent complex scenarios—such as the coexistence of multiple directional interferences, increased diversity and density of GNSS interference, and the presence of multiple low-power interference sources—conventional localization methods often fail to provide reliable results, thereby limiting their applicability in real-world environments. This paper presents a multi-interference sources localization method using object detection in GNSS C/N0 distribution maps. The proposed method first exploits the similarity between C/N0 data reported by GNSS receivers and image grayscale values to construct C/N0 distribution maps, thereby transforming the problem of multi-source GNSS interference localization into an object detection and localization task based on image processing techniques. Subsequently, an Oriented Squeeze-and-Excitation-based Faster Region-based Convolutional Neural Network (OSF-RCNN) framework is proposed to process the C/N0 distribution maps. Building upon the Faster R-CNN framework, the proposed method integrates an Oriented RPN (Region Proposal Network) to regress the orientation angles of directional antennas, effectively addressing their rotational characteristics. Additionally, the Squeeze-and-Excitation (SE) mechanism and the Feature Pyramid Network (FPN) are integrated at key stages of the network to improve sensitivity to small targets, thereby enhancing detection and localization performance for low-power interference sources. The simulation results verify the effectiveness of the proposed method in accurately localizing multiple interference sources under the increasingly prevalent complex scenarios described above.

<h3>Abstract</h3> The vulnerability of Positioning, Navigation, and Timing (PNT) services derived from Global Navigation Satellite Systems (GNSS) makes having a resilient and accurate Alternative PNT (APNT) based on high-power terrestrial radio sources necessary. The L-band is very crowded spectral real estate with GNSS, Distance Measuring Equipment (DME) and Air Traffic Control Beacon System (ATCRBS) signals occupying the band from 900–1600 MHz. Thus, as getting new signal and spectrum for APNT would be difficult, we must leverage existing transmissions and infrastructure. The ∼660 Automatic Dependent Surveillance-Broadcast (ADS-B) ground stations in the United States represent significant infrastructure that can be leveraged for APNT. However, as ADS-B was designed for surveillance, it does not inherently possess features necessary to support APNT goals. This paper describes and demonstrates techniques for using ADSB Universal Access Transceiver (UAT) signals for PNT. We develop methods to use all ground UAT signals to provide robust, multi-frequency pseudoranges. We examine the ranging and positioning performance of the UAT signal on the ground and in flight, to demonstrate its ranging accuracy, and hence the timing and synchronization of the station. We demonstrate and analyze navigation using UAT signals, as well as the intra-system interference challenges of using multiple UAT stations.

Automatic Dependent Surveillance-Broadcast (ADS-B) technology offers significant advantages in civil aviation applications, including high update rates, low construction and maintenance costs, and rich data content. However, its heavy dependence on the Global Navigation Satellite System (GNSS) renders it vulnerable to GPS interference, which can severely degrade data quality. To address this issue, it is necessary to optimize flight trajectories by incorporating feature values derived from ADS-B data. This paper proposes a flight path optimization method based on the ADS-B Navigation Integrity Category (NIC). First, features are extracted by analyzing the downlink data structure of ADS-B to filter out flight path points with low NIC values. Subsequently, radar data is dynamically integrated with the refined ADS-B data to enhance trajectory continuity during GPS interference events. Finally, the method is validated using real flight data, which also aids in the identification of GPS interference sources. The findings of this study can be applied to improve the quality of flight trajectories, trace the origins of GPS interference, optimize air traffic management efficiency, and significantly enhance aviation safety.

Technological independence is important for every country in global competition. One of the technological advancements developed by the Indonesian government through BPPT is Automatic Dependent Surveillance Broadcast (ADS-B) type in, which functions as a flight monitoring system. The Indonesian Air Force (TNI AU) through Depohar 50 (Depot Maintenance 50) has also developed ADS-B type in, which is currently deployed in six radar units known as the Flight Monitoring System (FMS) Mode-S. Accordance with government regulations (Minister of Transportation Regulation No. 81 of 2017), the government has mandated the use of ADS-B for flight safety. ADS-B has two types, in and out. In the TNI AU, ADS-B out is installed on aircraft such as Grob, KT-1, and Cessna, while ADS-B in is installed on Weibel radar. However, since ADS-B is not yet installed on TNI AU aircraft, flight data from the Air Traffic Control (ATC) was communicated to the pilots, hence, they can be aware of the air traffic situation. Furthermore, due to the increasing air traffic, communication with ATC has become limited. A qualitative method was used in the development of the ADS-B type in TNI AU aircraft, and the previous ADS-B type in development could only be installed on the ground station. The information received from ADS-B on the aircraft was real-time air traffic, which helps pilots make decisions to enhance flight safety, such as reducing the risk of aircraft collisions. The use of this technology on TNI AU aircraft is important for improving flight safety and technological independence.

국제해사기구(International Maritime Organization, IMO)에서는 선박의 해상 충돌을 방지하기 위하여 SOLAS의 요구조건에 따라 모든 선박에 대하여 선박자동식별장치(Automatic Identification System, AIS)를 의무적으로 장착하도록 권고하고 있다. AIS를 사용하면 타선에 대한 제원 및 항행정보의 획득이 가능하여 충돌방지뿐만 아니라 광역관제, 조난 선박의 탐색구조 등 안전관리에도 활용이 가능하다. 본 논문에서는 AIS 장비를 사용하여 ADS-B (Automatic Dependent Surveillance - Broadcast) 개념 기반의 항공감시용 송수신기를 구현한 결과에 대하여 살펴보도록 한다. 기본적으로 AIS는 해상에서 사용되기 때문에 고도 정보를 사용하지 않지만, AIS 장비 내부에 사용하는 GPS (Global Positioning System) 칩셋에서 제공하는 고도 정보의 추출이 가능하다. 고도 정보를 포함한 감시 메시지 형식을 정의하고, SOTDMA (Self-Organizing Time Division Multiple Access) 방식을 개선하여 ADS-B 송수신기를 구현하였다. 적용 결과를 확인하기 위하여 지상시험 및 비행시험을 수행하였다. International Maritime Organization (IMO) recommends the installation of an Automatic Identification System (AIS) according to requirements by SOLAS to avoid maritime collision. AIS provides traffic information of other ships that may be used for maritime traffic control, SAR (Search and Rescue) and collision avoidance to apply safety management. In this paper, preliminary results to implement an aeronautical surveillance transceiver using AIS transceiver based on ADS-B concepts are described. Although altitude information is not required for AIS since the AIS is operated at MSL (Mean Sea Level), altitude information can be extracted by a GPS (Global Positioning System) chip-set in the AIS transceiver. ADS-B transceiver is implemented by defining a surveillance message format including the altitude information and modifying SOTDMA (Self-Organizing Time Division Multiple Access) protocol. Ground tests and flight tests are performed to validate the implementation results.

Operations in the Next Generation Air Transportation System (NextGen) are planned to have a reduced dependency on primary surveillance radar and use Automatic Dependent Surveillance - Broadcast (ADS-B) to provide aircraft state information to Air Traffic Control (ATC) and onboard collision detection and avoidance systems. With the ongoing integration of Unmanned Aircraft Systems (UAS) in the National Airspace System (NAS), ADS-B is expected to become the main surveillance input to UAS collision avoidance. Traffic Alert and Collision Avoidance System (TCAS) is unable to meet requirements in terms of adaptability to future operations with reduced separation margins, addition of new user groups (e.g., UAS), and support of additional surveillance inputs. Airborne Collision Avoidance System (ACAS X) is being designed to meet these requirements and to increase surveillance, alerting, and resolution performance. The RTCA has released Minimum Operational Performance Standards (MOPS) to provide system and operational performance characteristics that ADS-B must provide. This paper analyzes recorded ADS-B data from test flights that were performed in the Continental U.S. (CONUS) and verifies measured performance with specified operational characteristics in terms of coverage, accuracy, and integrity.

The progressive development of navigation technology has significantly improved real-time positioning accuracy, addressing the needs of modern applications. GNSS (Global Navigation Satellite System) is the primary system used for precise positioning across various platforms. However, GNSS is susceptible to errors, particularly interference, which degrades signal quality and compromises accuracy. Auxiliary systems such as INS, gyroscopes, and map-matching algorithms enhance reliability during interference but depend on GNSS for initialization.&amp;#160;Signal detection algorithms, often employing CRPA (Controlled Reception Pattern Antennas) and advanced computational techniques, are essential for mitigating the impact of interferences and ensuring reliable navigation. This study compares the performance of two CRPA systems with different GNSS modules and algorithms, subjected to spoofing-jamming interference during experiments. The first CRPA, integrated with the u-blox ZED-F9P module, supports GPS, BeiDou, and Galileo satellites, employing an adaptive notch filter and pulse blanking. The second CRPA, featuring the Unicore UM980 module, supports GPS, BeiDou, and GLONASS satellites, utilizing a space-time algorithm alongside the JamShield adaptive mechanism for interference mitigation. In this study, real-time measurements were conducted on a car-mounted device platform under normal operating conditions. The platform was tested stationary for 5 minutes, followed by 15-minute intervals at speeds of 60 km/h. During each interval, 5 minutes of jamming and 5 minutes of spoofing were applied, with independent spoofing signals introduced. Jamming signals reached up to 50 dB-Hz, and spoofing signals were applied at levels up to 32 dB-Hz using a specialized interference device. During constant-speed travel, the second CRPA tracked 28 satellites with an HDOP of 0.5, while the first CRPA tracked 23 satellites with an HDOP of 0.75. Under jamming conditions, The second antenna maintained consistent satellite visibility, whereas the first experienced a pronounced decline in the number of observable satellites. Similarly, spoofing had no adverse effect on the second antenna, but the first suffered reduced satellite counts and positional accuracy.&amp;#160;Additionally, the first antenna consistently underestimated the vehicle&amp;#8217;s speed by approximately 5 km/h and exhibited a speed fluctuation of 0.5 m/s under interference conditions.&amp;#160;

The increasing congestion of commercial airspaces necessitated more efficient air traffic control (ATC) methods. The Automatic Dependent Surveillance-Broadcast (ADS-B) protocol is at the heart of the next-generation of ATC systems and is currently being rolled out in most countries. With ADS-B, an aircraft determines its own position by using global navigation satellite systems and broadcasts it periodically over the 1090-MHz radio frequency to ground stations or other aircraft in proximity. This approach increases the accuracy of aircraft localization and enables lower separation requirements and improved situational awareness for pilots and controllers. At the same time, it is supposed to significantly reduce the costs of air traffic surveillance compared with former independent surveillance radar systems.

ADS-B (Automatic Dependent Surveillance – Broadcast) involves broadcasting the latitude, longitude, altitude, velocity, identification and other information from on-board systems. Any suitable receiver may receive and process these broadcasted messages, which can be an ADS-B Ground Station which processes the ADS-B messages and generates aircraft reports to be used by Air Traffic Controllers.

An adaptive Kalman filter-based frequency estimation algorithm is proposed to track the frequency of a chirp-type global navigation satellite system (GNSS) interference. The unknown interference frequency of GNSS in the received signal can be estimated by using received samples in the time domain, but the thus-obtained value can include a large amount of error caused by measurement noise and by the frequency change rate of the interference. In order to reduce the error, an adaptive fading Kalman filter that is based on the Fourier series is applied in the proposed algorithm. Furthermore, an optimal order-reduction algorithm is proposed to select the appropriate order of the Fourier series for the type of received interference. The performance of the tracking algorithm is verified by making comparisons with conventional algorithms. The proposed algorithm has better tracking performance than conventional algorithms when the jammer-to-signal ratio (J/S) is more than 30 dB, which would seriously affect the accuracy of the GNSS. Copyright © 2018 Institute of Navigation

In this paper, we research the feasibility of using high rate Automatic Dependent Surveillance – Broadcast (ADS-B) aircraft altitude and velocity information to detect the presence of mountain waves and Mountain Wave Turbulence (MWT) in the vicinity of steep terrain as well as atmospheric waves and turbulence from other sources that are of interest to aviation, for instance, Convective Induced Turbulence (CIT). The key element of ADS-B that enables the research is a 1 second update rate on ADS-B position reports, and aircraft position and altitude being reported based on Global Positioning System (GPS) accuracy. This frequency is much faster than today’s standard of reporting meteorological data via the Aircraft Meteorological Data Relay (AMDAR) or Meteorological Data Collection and Reporting System (MDCRS), and as we show, is fast enough to estimate the location of mountain wave events, MWT, and CIT. When combined with other weather state information gained by in situ sensors, satellite, and radar-based technology in the National Airspace System (NAS), a total situational awareness of mountain wave, MWT, and CIT information in the Continental United States (CONUS) can be achieved for supporting airline flight planning and Air Traffic Management (ATM) decision making.

This paper presents a system in concept development that combines the integrity of the civil automatic dependant surveillance - broadcast (ADS-B) system for air-to-air conflict avoidance and air traffic management (ATM) surveillance with the military secure Mark XIIA Mode 5 Identification Friend or Foe (IFF) system as the data link. This new system, coined Military ADS-B (MADS-B), expands the traditional IFF surveillance data of range, azimuth, altitude, and identity (ID) to include each platformpsilas dynamic state of motion and status. This self-reporting system significantly improves positioning and status data between Tri-Service platforms and with Allies - who are also transitioning to the common Mode 5 system. Beyond MADS-Bpsilas securing of ADS-B data, it enables overcoming other surveillance and navigation shortfalls through future software based message additions. The paper summarizes ADS-B operations, the conversion of data to the Mode 5 Level 2 formats, and examples of message extensions providing surveillance enhancements.