ADS-B Messages Research Articles

GNSS interference detection: Methodology utilising ADS-B NACp indicator and GPS almanac data

Abstract The threat of GNSS interference poses a great danger to many critical infrastructure systems including air navigation. With a focus on mitigating this threat, this paper proposes a methodology for detecting GNSS interference. The methodology utilises the quality indicator NACp transmitted in ADS-B messages and GPS almanac data for interference detection. The NACp indicator enables estimation of the position error derived from GPS, which is compared with the HDOP value of the GPS satellite constellation. Based on this comparison, the developed detection algorithm determines whether the aircraft is affected by jamming. The detection methodology is evaluated on datasets obtained during deliberate experiments with GPS jamming. The proposed methodology provides a way to detect GNSS interference, facilitating mitigation of its impact on air traffic operation.

Research on ADS-B spoof detection technology based on radio spectrum features

Abstract This paper discusses and analyzes the 1090ES mode ADS-B and examines the airborne ADS-B transponder and ground monitoring sensing nodes. The ADS-B signal receiver structure converts the received radio signal to a zero IF signal for digital filtering to obtain phase information. The cognitive radio spectrum monitoring technology mainly uses periodic characteristic monitoring to maximize the network's security in the era of artificial intelligence. For a set of ADS-B messages from the same source, the correlation coefficients of the two variation amounts are carried out to discriminate between real targets and spoofed interference, and the source consistency detection method is used to reduce the probability of false alarms. The results show that when the number of signal bars is greater than 11, the correlation value of the real signal is greater than 0.61, while the correlation value of the spoofed signal is around 0.22, which can be better distinguished.

An ADS-B Information-Based Collision Avoidance Methodology to UAV

A collision avoidance method that is specifically tailored for UAVs (unmanned aerial vehicles) operating in converging airspace is proposed. The method is based on ADS-B messages and it aims to detect and resolve conflicts between UAVs. The proposed method involves two main steps. First, a UAV conflict-sensing scheme is developed, which utilizes ADS-B information flow path and analyzes the message format information. Second, an unscented Kalman filter is used to predict UAV trajectories based on the acquired ADS-B information. The predicted information is then used to determine potential conflict scenarios, and different deconfliction strategies are selected accordingly. These strategies include speed regulation, direction regulation, and compound deconfliction, and are mathematically validated using the velocity obstacle method. The feasibility and effectiveness of the proposed method are evaluated through simulation, and it is concluded that the method can significantly improve the conflict resolution capability of UAV flights. This research provides a valuable contribution to the field of UAV collision avoidance, and can serve as a theoretical foundation for further advancements in this area.

МОДИФИЦИРОВАННАЯ МЕТОДИКА ПОДТВЕРЖДЕНИЯ ДАННЫХ АЗН-В С КОРРЕКЦИЕЙ ТЕМПЕРАТУРЫ ПРИ ОЦЕНКЕ ВЫСОТЫ ПОЛЕТА (ЧАСТЬ 1)

The International Civil Aviation Organization indicates the need to confirm the ADS-B data. The ADS-B messages include information about the horizontal and vertical location. Information about the altitude of an aircraft in civil aviation is of great importance. The article proposes a modified methodology for confirming ADS-B data when performing flights on local airlines, which allows us to estimate and compare the geometric and barometric altitude of aircraft flight transmitted in a standard ADS-B message. The proposed modification of the method consists is correcting the temperature values, using the full barometric Laplace formula, taking into account the ADS-B quality parameters. In a level flight, with no ground velocity vector data, temperature is corrected using the airspeeds (TAS, IAS) transmitted in the ADS-B message. The method uses a maximum permissible error of 90 m. It is also proposed to determine the air temperature according to geometric and barometric altitude data transmitted in the standard ADS-B message. The determination of air temperature at altitudes involves the use of the ADS-B data from the aircraft that completed take-off. To determine the temperature according to the data of the aircraft completed landing, statistics of data from several aircraft is needed.

ИСПОЛЬЗОВАНИЕ МЕТОДА TDOA ДЛЯ ПОДТВЕРЖДЕНИЯ ДОСТОВЕРНОСТИ ИНФОРМАЦИИ РАДИОВЕЩАТЕЛЬНОГО АВТОМАТИЧЕСКОГО ЗАВИСИМОГО НАБЛЮДЕНИЯ

The paper considers the possibility of using the Time Difference of Arrival (TDOA) method, which can be applied to confirm the reliability of information coming from multiple sources. TDOA method can be applied to validate the information received from several ground automatic dependent surveillance stations of broadcast type (ADS-B). The paper is aimed at studying the TDOA method and its application to ADS-B stations. This method makes it possible to use the ADS-B as the only means of surveillance at the airfield. Currently, according to ICAO recommendations, ADS-B stations are not allowed to be used as a stand-alone surveillance aid due to the problems related to the possibility of distorting a signal or introducing some false information into messages, so the operation of this type of stations is possible only together with other means of surveillance, such as multi-position surveillance systems (MLAT) or secondary surveillance radar systems (SSR) thus increasing the cost of organizing surveillance on the airfield. Thus, the relevance of the work is related to the need to find an alternative method of confirming the validity of an ADS-B message.

МЕТОД ОБЕСПЕЧЕНИЯ ЗАЩИТЫ ПЕРЕДАВАЕМЫХ СООБЩЕНИЙ В СИСТЕМЕ ADS-B С ИСПОЛЬЗОВАНИЕМ АППАРАТА КЛЕТОЧНЫХ АВТОМАТОВ

The purpose of the study is to develop a method for encoding of transmitted ADS-B messagesbetween aircraft. The open format 1090ES of transmitted data is critical in terms of carryingout various types of attacks that can lead to a violation of the safety of aircraft operations.The work is aimed at using means of encoding and decoding messages with a private key. Researchmethods are based on the application and development of streaming data encryption usingone-dimensional cellular automata. They operate as a generator of pseudo-random sequences thattransform the elementary states of a cell of a one-dimensional cellular automaton based on typicalhardware-oriented operations. The processes of encoding and decoding data fields are based onan analytical expression using typical logical operations (or, xor). This property allows parallelprocessing of message data fields. The result is the created method for ensuring the protection oftransmitted data, additionally encoding on transmission and decoding on message reception.A distinctive feature of the method is the preservation of the protocol forma. The method uses aone-dimensional cellular automaton that encodes and decodes the target fields (coordinates, heading,etc.) using a pseudo-random number generator. The developed method belongs to the class ofhardware-oriented methods. Critical for encoding and decoding properties of periodicity of datafields and key length are eliminated by choosing an initial irrational value and organizing the“streaming” work of the encoder. If the encoding automaton is running in streaming mode, thecurrent value depends on the history of some depth, determining the length of the "automatic key"from the ADS-B message will be algorithmically impossible due to data loss. The linear complexityof the method allows you to perform transformations at the data rate. Conclusion: the developmentof hardware-oriented methods of data encoding makes it possible to increase the efficiency ofusing the ADS-B system by counteracting various types of destructive actions.

COMPARATIVE STUDIES OF METHODS FOR IMPROVING THE CYBER SECURITY OF UNMANNED AERIAL VEHICLES WITH THE BUILT-IN ADS-B SYSTEM

The subject of study in the article is methods for improving the cybersecurity of unmanned aerial vehicles with an integrated ADS-B system. The aim is to analyze and compare methods for improving the cybersecurity of unmanned aerial vehicles with an embedded ADS-B system. Particular scientific tasks: analysis and comparative studies of the main types of cyber threats and methods for improving the cybersecurity of unmanned aerial vehicles with an integrated ADS-B system, the development of an appropriate taxonomy, and the development of proposals for further research. The methods used in the article are the methods of system analysis. The following research results have been obtained: a classification of cyber threats to the security of unmanned aerial vehicles with an integrated ADS-B system has been developed; a taxonomy of ADS-B message modification and injection attacks has been developed; practical UAV security metrics adapted to the presented taxonomy of cyberattacks are defined and researched ; chosen most priority directions research ; - a generalized classification of cryptographic protection methods adapted to solve the problems of improving the security of UAVs with an integrated ADS-B system has been developed; the use of additional means of identification based on steganographic methods of data protection is proposed. Conclusions. An analysis and comparative studies have been carried out, and a generalized classification of methods for improving the cybersecurity of unmanned aerial vehicles with an integrated ADS-B system has been developed. Their advantages and disadvantages are revealed, which made it possible to determine the priority of further research and possible promising ways to solve the tasks.

Verification of influence of the solar flare from September 2017 to ADS-B NAC parameter

This paper dissertates about the influence of space weather event from September 2017 on parameters NAC and NIC in ADS-B messages. Space weather have potential to influence GNSS navigation. Especially in the aviation, where we depend on th GNSS more. Therefore we examined the influence of solar flares on the aviation navigation system of commercial aircraft. We used data broadcasted by ADS-B system during the most severe space weather event. Parameters NAC and NIC describe the level of reliability of the aircraft position information based on the GNSS. Therefore, they might be partially used as sensors of any irregularities in GNSS signal. We focus on these parameters during one of the most severe solar flare in recent years to establish if there is any observable influence of the space weather on these parameters. We were able to prove that even during this severe flare that there was no degradation in the availability of the GNSS.

Method for determining coordinates of airborne objects by radars with additional use of ADS-B receivers

The method of determining coordinates of an airborne object using ADS-B receivers was improved. The method involves the following sequence of actions: input of initial data, measurement of coordinates of the airborne object by the radar, checking the availability of data about the airborne object obtained from the ADS-B receivers. In the absence of such data, coordinates of the airborne object are determined only from the data of the radar. The airborne object mark was identified according to information from the radar and the ADS-B receivers. Unlike the known methods, the advanced method of determining coordinates of an airborne object by a radar additionally uses information from the ADS-B receivers. The ADS-B receiver signals were experimentally studied. It was found that the ADS-B receiver has received more than 6,000 messages about airborne objects in a single day. It was established that information about the location of the airborne object contained in ADS-B messages was encoded in CPR format. An algorithm for decrypting the ADS-B messages with a global connection of an airborne object to geographical coordinates was presented. An algorithm for detecting signals of onboard transponders of ADS-B airborne objects was presented. Non-standard ADS-B messages from airborne objects were studied. It was suggested that some short non-standard ADS-B messages were received from small and military airborne objects. Accuracy of determining coordinates of airborne objects by the radar with additional use of the ADS-B receiver was estimated. Dependence of the root mean square error of determining the airborne object coordinates on a distance to the airborne object was presented for various cases. It was established that the accuracy of determining the airborne object coordinates can be raised from 36 % to 67 % depending on the distance to the airborne object

ADS-B Crowd-Sensor Network and Two-Step Kalman Filter for GNSS and ADS-B Cyber-Attack Detection.

Automatic Dependent Surveillance-Broadcast is an Air Traffic Control system in which aircraft transmit their own information (identity, position, velocity, etc.) to ground sensors for surveillance purposes. This system has many advantages compared to the classical surveillance radars: easy and low-cost implementation, high accuracy of data, and low renewal time, but also limitations: dependency on the Global Navigation Satellite System, a simple unencrypted and unauthenticated protocol. For these reasons, the system is exposed to attacks like jamming/spoofing of the on-board GNSS receiver or false ADS-B messages’ injection. After a mathematical model derivation of different types of attacks, we propose the use of a crowd sensor network capable of estimating the Time Difference Of Arrival of the ADS-B messages together with a two-step Kalman filter to detect these attacks (on-board GNSS/ADS-B tampering, false ADS-B message injection, GNSS Spoofing/Jamming). Tests with real data and simulations showed that the algorithm can detect all these attacks with a very high probability of detection and low probability of false alarm.

AirSync: Time Synchronization for Large-Scale IoT Networks Using Aircraft Signals

The prosperity of Internet of Things (IoT) brings forth the deployment of large-scale sensing systems such as smart cities. To enable the collaboration tasks among distributed devices, time synchronization is crucial. However, due to the long-range and device heterogeneity, accurate time synchronization for a large-scale IoT network is challenging. Existing GPS or NTP solutions either require an outdoor environment or only have low and unstable accuracy. In this paper, we propose AirSync, a novel synchronization method that leverages the widely existed aircraft signals, ADS-B, to synchronize large-scale IoT networks with nodes even in indoor environments. But ADS-B messages have no time stamp and cannot provide a reference time. We leverage the continuity of aircraft movements to estimate the aircraft traveling time. Then devices that observe common aircraft moving segments can calculate their time offset. To obtain the time skew, we propose a combined aircraft linear regression method. We also design a transitive synchronization for devices that cannot observe common aircraft. Besides, we also design a duty-cycled ADS-B message collection method for resource-limited IoT devices. We implement a prototype of AirSync and evaluate its performance in various real-world environments. The results show that AirSync can obtain the sub-ms accuracy.

A domain-specific language to design false data injection tests for air traffic control systems

The ADS-B—automatic dependent surveillance-broadcast—technology requires aircraft to broadcast their position and velocity periodically. As compared to legacy radar technologies, coupled with alarming cyber security issues (the ADS-B protocol provides no encryption nor identification), the reliance on aircraft to communicate this surveillance information exposes air transport to new cyber security threats, and especially to FDIAs—false data injection attacks—where an attacker modifies, blocks, or emits fake ADS-B messages to dupe controllers and surveillance systems. This paper is part of an ongoing research initiative toward the generation of FDIA test scenarios and focuses on supporting the test design activity, i.e., supporting ATC experts to meticulously craft test cases in order to assess the resilience of surveillance systems against FDIAs. To achieve this goal, we propose a complete and powerful domain-specific language (DSL), close to natural language, that provides a large expressiveness to support ATC business experts in creating FDIA’s test scenarios. We demonstrate the design capabilities of this approach and its productivity gain with respect to manually creating the FDIAs test scenarios.

Implementation of a Long-Range Air Traffic Flow Management for the Asia-Pacific Region

We provide a concept of operations and a corresponding implementation of a long-range air traffic flow management in the Asia-Pacific region. This management will provide an appropriate demand-capacity balancing considering both aircraft sequencing by local arrival management procedures and flow optimization to prevent over-demand in the approach area around the airport. Thus, coordination of long-range international flights demands collaboration between different flight information regions and local regulations. As Singapore Changi Airport is a central element of the Asia-Pacific flow management high share of long-haul air traffic, we use this airport to demonstrate our approach. To derive the operational conditions and actual traffic patterns at the airport, ADS-B messages and flight plan information are processed. The data are cleaned, analyzed, and filtered to provide information about arrival flows within given distances to the airport. We provide an efficacy analysis of the long-range air traffic flow management using two approaches. First, we applied a mixed-integer optimization of time shifts of normal distributed flight times. Here, the regulation of long-range flights by time shifts (e.g., achieved by speed advisories) shows a significant relief from periods of over-demand at the airport approach sector. Second, we implement a reference and a test case scenario in an agent-based simulation environment including the local arrival management procedures. Here, the number of holdings and the associated holding time could be reduced by at least 26%.

Data Reception Analysis of ADS-B on Board the TianTuo-3 Satellite

Aircraft information can be easily integrated to Internet of Things by ADS-B technology. The spaceborne ADS-B receiver equipped with TianTuo-3 satellite has realized China’s first aircraft surveillance from space, it has been working well and stably receiving over 100 million ADS-B messages from global aircraft during last four years. In this paper, the data obtained by the TianTuo-3 ADS-B receiver is analysed in detail, including statistical analysis on the detection probability, the proportion of all types of aircraft, the increasing rate of aircraft in the world. These results demonstrated that satellite ADS-B system provides an all-around safety and surveillance to air traffic management, and it can help in rescuing, surveying, or tracking of special aircraft, or analysing world flight for economic studies.

Metode Deteksi ‘Potential Security Threats’ Pada ADS-B Data dengan Memonitor EM Emisi Radiasi pada Jaringan Ethernet

Precision, Navigation, and Timing (PNT) system based on Global Navigation Satellite System (GNSS) becomes significant in the air traffic management, especially in the use of Automatic Dependent Surveillance Broadcast system (ADS-B) for air traffic monitoring. Therefore the integrity of GNSS is significant to provide a reliable data necessary for ADS-B. GNSS Interference due to intentional or unintentional surrounding signal source may decrease the integrity of GNSS signal and therefore may result in the in-accurate position data of ADS-B message. ADS-B message itself is also vulnerable from potential security threats in their network. This paper proposed a methodology to detect potential security threats of ADS-B network system for both GNSS signal and ADS-B data by measuring and monitoring the electromagnetic radiated emission from ethernet cable IPv4 Cat5.

Multidevice False Data Injection Attack Models of ADS-B Multilateration Systems

Location verification is a promising approach among various ADS-B security mechanisms, which can monitor announced positions in ADS-B messages with estimated positions. Based on common assumption that the attacker is equipped with only a single device, this mechanism can estimate the position state through analysis of time measurements of messages using multilateration algorithm. In this paper, we propose the formal model of multidevice false data injection attacks in the ATC system against the location verification. Assuming that attackers equipped with multiple devices can manipulate the ADS-B messages in distributed receivers without any mutual interference, such attacker can efficiently construct attack vectors to change the results of multilateration. The feasibility of a multidevice false data injection attack is demonstrated experimentally. Compared with previous multidevice attacks, the multidevice false data injection attacks can offer lower cost and more covert attacks. The simulation results show that the proposed attack can reduce the attackers’ cost by half and achieve better time synchronization to bypass the existing anomaly detection. Finally, we discuss the real-world constraints that limit their effectiveness and the countermeasures of these attacks.

Пасивний метод позиціонування за інформацією далекоміра та цифрових повідомлень у форматі автоматичного залежного спостереження

Мета: представлені результати досліджень спрямовані на розробку нового методу позиціонування, що використовує сигнали DME в просторі та повідомлення ADS-B від користувачів повітряного простору. Запропонований підхід позиціонування базується на зборі та аналізі сигналів. Один літак, що взаємодіє з двома різними DME, є джерелом трьох гіперболічних ліній розташування, перетин яких може вказувати на розташування користувача. Методи дослідження: представлений підхід ґрунтується на використанні різницево-далекомірному методу, статистичних методах оцінки похибок та комп'ютерному моделюванні. Результати: запропонований метод виявлення координат літальних апаратів може зменшити навантаження на наземну мережу DME, оскільки він базується на пасивному спостереженні сигналів DME, присутніх у повітряному просторі. Обговорення: Підхід може бути застосований в алгоритмах обчислювальної системи літаководіння у якості альтернативного методу позиціонування до існуючих.

Design and Implementation of Spaceborne ADS-B Message Detection Algorithm

ADS-B message detection requires a simpler and less resource consuming algorithm when applied to satellites. In this paper, to address the defects of the traditional S-mode message detection algorithm that is verified repeatedly causing the real-time problem or uses too much FPGA resource to be detected more quickly, the paper focus on the ADS-B S-mode message preamble detection and data bit extraction algorithm design and implementation. The preamble detection algorithm based on preamble correlation and the data bit extraction algorithm is designed on the simulation platform established by MATLAB/Simulink, and the hardware implementation of FPGA is completed. The design of the equipment is optimized for the shortage of space equipment resources in the timing control, bit process and the CRC check. The results show that the algorithm not only can effectively detect the preamble of S-mode messages, but also performs accurate data bit extraction and completes the detection of ADS-B messages. It is also suitable for hardware implementation and requires less hardware resources. Results indicate that it is suitable for application in spaceborne ADS-B receiving system.

Using LSTM encoder-decoder algorithm for detecting anomalous ADS-B messages

Although the ADS-B system is expected to play a major role in the safe navigation of airplanes and air traffic control (ATC) management, it is also well known for its lack of security mechanisms. Previous research has proposed various methods for improving the security of the ADS-B system and mitigating associated risks. However, these solutions typically require the use of additional participating nodes or sensors (e.g., to verify the location of the airplane by analyzing the physical signal) or modification of the current protocol architecture (e.g., adding encryption or authentication mechanisms). Due to the regulation process regarding avionic systems and the fact that the ADS-B system is already deployed in most airplanes, applying such modifications to the current protocol at this stage is impractical. In this paper we propose an alternative security solution for detecting anomalous ADS-B messages, which is aimed at the detection of spoofed or manipulated ADS-B messages sent by an attacker or compromised airplane. The proposed approach utilizes an LSTM encoder-decoder algorithm for modeling flight routes by analyzing sequences of legitimate ADS-B messages. Using these models, aircraft can autonomously evaluate ADS-B messages received and identify deviations from the legitimate flight path (i.e., anomalies). We examined our approach on thirteen different flight route datasets into which we injected different types of anomalies. In addition, we compared our proposed method with five commonly used anomaly detection algorithms: GMM-HMM, DBSTREAM, one class SVM, LOF and Isolation Forest. Our experiments show that by using our approach, we were able to detect all of the injected attacks with an average false alarm rate of 4.5%. Moreover, in all cases, the performance of the LSTM encoder-decoder algorithm outperformed the other algorithms.

ADS-B vulnerabilities and a security solution with a timestamp

Automatic Dependent Surveillance-Broadcast (ADS-B) is the foundation of NextGen Air Traffic Control (ATC) system, and all aircraft must be equipped with it by January 1, 2020. Despite the importance of ADS-B, it has been developed without security considerations and is subject to various types of attacks. A trustworthy system will make the NextGen system more reliable and make air transportation safer. But current safety measures are inadequate and many research proposals are not yet practical or cost-effective. We developed a practical method that can reject virtually all spoofed messages by monitoring the signal propagation time between senders and receivers. To measure the actual propagation time, the method uses a small timestamp value; hence, we call it ADS-B with Timestamp (ADS-BT). ADS-BT monitors the discrepancy between the time of flight based on the timestamp values and the time of flight based on the location data. In spoofed ADSB messages, the discrepancy between the two diverges over time, which allows us to identify spoofed messages accurately.