Distance Measuring Equipment Signals Research Articles

Physical Layer Security for L-Band Digital Aeronautical Communication System with Interference Mitigation

As one of the main candidates for future civil aviation communications systems, the L-band digital aeronautical communication system (L-DACS) is expected to achieve secure and reliable transmission. Due to the broadcasting nature of air–ground wireless links, the L-DACS has the risk of being intercepted by malicious eavesdroppers, which negatively affects aviation communication security. In addition, because the spectrum of the L-DACS overlaps with the aviation distance measuring equipment (DME), the pulse interference caused by the DME signal may lead to the wireless link being more fragile and susceptible to wiretapping. In this paper, with a focus on enhancing wireless transmission security, we propose a comprehensive physical layer security (PLS) method for the L-DACS. The key to the proposed PLS method is restraining the transmission of the eavesdropper by injecting artificial noise into the transmitted signal while improving the transmission of the legitimate receiver through the adoption of pulse interference mitigation. First, to characterize the L-DACS in the secure scene, we derive the signal-to-interference-plus-noise ratio (SINR) of the legitimate receiver and any potential eavesdropper by constructing equivalent noise. Next, from the perspective of the information theory, we derive the closed form of the secrecy capacity of the L-DACS by employing the proposed PLS methods with three kinds of nonlinear interference mitigation: including ideal pulse blanking, peak threshold-based pulse blanking, and peak threshold-based pulse clipping. Finally, we compare and analyze different ways to enhance the secrecy capacity of the proposed PLS method using various interference mitigation methods.

К ВОПРОСУ ПРИМЕНЕНИЯ ЗАКОНА АБЕРРАЦИИ В РАДИОНАВИГАЦИИ И АВИАЦИОННОМ НАБЛЮДЕНИИ

The author analyzes the potential use of the aberration law which describes the deviation of measured parameters of an observed object as it changes its position relative to the observer. The law was studied in terms of its application in radio navigation and aircraft surveillance. During research the author obtained dependences of deviations of observable and real (true) characteristics of an observed object for such aids of radio-technical support of flights as a primary radar, distance measuring equipment (DME) and a ground station of automatic dependent surveillance. In doing so, the speed of the observed object was set equal to 250 m/s (typical for existing airplanes) and 600 m/s (specific for perspective supersonic airplanes). It follows from the calculations that the aberration effect cannot be detected for determining slant range or pulse duration tasks due to the imperfection of the existing measuring instruments. However, the aberration effect can be detected in the tasks of determining the time interval between probing pulses of the primary radar or automatic dependent surveillance messages, as well as in the determination of the frequency of the DME signal. This is achieved due to a sufficiently large dynamic range of the measured values. For the method of evaluating the aberration effect given in the paper the author performed estimation of the sensitivity to the errors of the measured value and the velocity of the observed object. The research confirmed possibility to apply the law of aberration in practice for radio navigation aids and aircraft surveillance, which can increase accuracy of position-fixing and determination of aircraft movement parameters as well as to expand capabilities of the available equipment.

AIRCRAFT POSITIONING USING MULTIPLE DISTANCE MEASUREMENTS AND SPLINE PREDICTION

During the crucial phases of take-off, initial climb, approach, and landing where aircraft are close to the ground, Global Navigation Satellite Systems (GNSS) signal strength may not be sufficient to guarantee safe operation, especially in the presence of potential interference, malicious or otherwise, from ground equipment. When the GNSS location is lost, aircraft typically revert to other navigation aids. The most accurate navigation aid is Distance Measuring Equipment (DME). However, whereas GNSS location is triangulated, the navigation equipment on-board aircraft can only measure two DME signals simultaneously. Therefore, location based on DME tends to be accurate only to hundreds of meters, compared to meters for GNSS. A new approach is presented for positioning using multiple DMEs. The approach is based on regression analysis for prediction of DMEs distances in time of measurement. This approach increases positioning accuracy due to availability of multiple DMEs data in the system of navigation equations. Spline functions were used in a regression model in order to achieve the most accurate prediction values. An approach was verified using real flight data and shown the decreasing of navigation system error on value depending on availability and geometry of ground stations locations.

Heuristic search for multi‐distance measuring equipment station selection

To support alternative positioning, navigation and timing (A-PNT), multi-DME with better geometry than distance measuring equipment (DME)/DME can be used to improve the performance. Different from the existing station selection methods that have been proposed for DME/DME, a station selection method for multi-DME should be considered in order to prevent unnecessary emission of navigation signals because DME receivers have limited number of channels and constrained real-time processing power, and also to limit DME to GNSS L5/E5a interference. A heuristic algorithm is constructed to determine the quasi-optimal selection of DME stations based on geometrical and computational cost restrictions, which is different from a brute-force method checking all possible subsets and selecting the best one. A station selection method for multi-DME is proposed based on the heuristic search. Meanwhile, the degradation of GNSS L5/E5a signal processing that is caused by DME signals is discussed. An advanced station selection method where the DME to GNSS signal interference is taken into account is also proposed. The experimental results show that the methods based on heuristic search can effectively select the quasi-optimal subset of DME stations with less computational expense.

Simulation and Research of DME Signal Coverage

In civil aviation land-based navigation equipment, the DME(Distance Measuring Equipment) system is a widely used short-range navigation equipment. Through the research on the antenna of the DME equipment, the antenna signal of the DME equipment is modeled and simulated, and the electromagnetic signal three-dimensional pattern of the DME equipment and the corresponding pattern of the E plane are obtained. On the basis of mastering the antenna signal radiation characteristics of each navigation device, the DME coverage area is simulated and analyzed.

A Method for Analyzing the Impact of Intra-System and Inter-System Interference on DME Based on Queueing Theory.

In order to use Distance Measuring Equipment (DME) properly, the impact of intra-system and inter-system electromagnetic interference must be analyzed firstly. However, the error of interference analysis using present methods based on pulse overlap is large when there are more aircraft. The aim of this article is to study a method of analyzing interference on DME whether the number of aircraft is small or not. According to the flow chart of DME signal, we studied the limitations of present methods; then constructed a model of analyzing the collision between duration of desired signal and dead time of receiver based on M/M/1/0 queueing system. Combing this model with other methods, we present a analytic model of analyzing intra-system and inter-system interference on DME. Using this analytic model, we analyzed reply efficiency (RE) and capacity of DME under intra-system and Joint Tactical Information Distribution System (JTIDS) interference. The result shows that the calculation for the probability of overlap between DME dead time and subsequent signals using queueing model agrees well with simulation. Consequently, the analytic model is more accurate than using a single method to analyze interference on DME.

Cancelation of Distance Measuring Equipment Interference for Aeronautical Communications

The L-band digital aeronautical communications system (L-DACS1) is subject to strong interference caused by distance measuring equipment (DME). For efficient statistical processing of interference, we adopt a Gaussian mixture (GM) distribution to model the impulsive nature of DME signals. Hence, we drive the parameters of the GM model in terms of properties of DME signals. This allows us to redesign the optimum receiver for mitigating DME interference. We also provide a simple pulse detector to estimate the presence of DME signals utilizing the null subcarriers of the L-DACS1.

Distance measuring equipment interference suppression based on parametric estimation and wavelet-packet transformation for global navigation satellite systems

It is well known that some global navigation satellite system (GNSS) signals operate on the aeronautical radionavigation services (ARNS) frequency band, which is also utilized by other aeronautical service signals, such as pulsed signals from the distance-measuring equipment (DME) system. Thus, the high-power DME signal, as interference, will significantly degrade the performance of the GNSS. Some algorithms, including time blanking, frequency notch filtering, and hybrid filtering, have been proposed to suppress DME interference. However, when the density of the DME pulse is high, they will bring a huge loss of the desired satellite signal. This paper proposes a hybrid approach for DME interference suppression by combining a novel parametric algorithm and the wavelet-packet-based algorithm. An overlap detection algorithm is also proposed to automatically switch between the two algorithms. When there is no overlapped pulse, the parametric method will be utilized to suppress the interference and retain more of the desired satellite signal. For overlapped DME pulses, the interferences are suppressed by the wavelet-packet transformation algorithm. The problem of parameter selection for wavelet-packet transformation is also discussed systematically. The trade-off between performance and complexity is obtained by adaptively selecting between the traditional algorithm and the proposed hybrid approach based on a pulse density detection algorithm. Numerical results are presented to demonstrate the effectiveness of the proposed approach.