Search Results (5)

This research investigates the positioning performance of the L-band Digital Aeronautical Communications System (LDACS) and presents a system architecture based on carrier-smoothed ground-to-air pseudoranges (PRs), along with clock corrections derived from asymmetric two-way time and frequency transfer (A-TWTFT) filters. The objective is to achieve required positioning accuracy and integrity for aviation operations, addressing the complexities associated with utilizing a terrestrial communications system for complementary positioning, navigation, and timing (CPNT). Through error covariance analysis, this study assesses the steady-state value, convergence time, and bounding performances of the filters. The positioning performance highlights the benefits provided by the proposed architecture. Full article

The L-band digital aeronautical communication system (LDACS) is one of the candidate technologies for future broadband digital aeronautical communications, utilizing the unused L-band spectrum between distance measuring equipment (DME) channels. However, the higher signal power of DME complicates LDACS implementation. This paper proposes an advanced DME mitigation approach for the LDACS, integrating joint direction of arrival (DOA) estimation with adaptive beamforming techniques. The proposed method begins by exploiting the cyclostationary characteristics of signals, accurately obtaining the preliminary direction of the LDACS signal using the Cyclic-MUSIC method. Subsequent precise steering vectors (SVs) are selected through Capon spectrum search, followed by the reconstruction of the interference plus noise covariance matrix (INCM). Using the obtained SV and INCM, the weight vector is calculated and beamforming is performed. Simulation results validate that the proposed method not only accurately estimates the direction of LDACS signal but also efficiently mitigates DME interference, demonstrating a superior performance and reduced algorithmic complexity, even in scenarios with lower signal-to-noise ratios (SNRs) and the presence of DOA estimation errors. Additionally, the proposed method achieves a low bit error rate (BER), further validating its ability to ensure communication quality and enhance the reliability of LDACS. Full article

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. Full article

Interference mitigation in L-band Digital Aeronautic Communication Systems (LDACS) from legacy users is extremely important as any error in data retrieval of aeronautic communication can adversely affect flight safety. This paper proposes an LDACS receiver prototype which uses rank-ordered absolute differences (ROAD) statistics to detect the distance measuring equipment (DME) interference. The detected DME interference is reduced in the next stage by pulse blanking. The performance of the proposed ROAD pulse blanking method (ROAD PB) is compared with the existing interference mitigation methods which use the amplitude of the received signal for the detection of DME interference. In depth analysis of the obtained results affirms that the proposed ROAD value-based interference detection excels amplitude-based detection. For an SNR value of 0 dB, the proposed method of detection could achieve a 3% increase in terms of accuracy with a reduction of 4% in false alarms. With the advantage of ROAD statistics detection, the proposed ROAD PB could achieve an SNR saving of 2.7, 1.1, 0.7, 0.25 and 0.2 dBs at BER ${10}^{-1}$ in comparison with pulse blanking, Genie-aided estimation enhanced pulse peak attenuator (GAEPPA), GAE enhanced pulse peak limiter (GAEPPL), optimum Bayesien estimator enhanced pulse peak attenuator (OBEPPA) and OBE enhanced pulse peak limiter (OBEPPL). The comparative results show that the proposed ROAD pulse blanking outperformed the other techniques for the optimum threshold value of the operation. Full article

Interference mitigation in L-band digital aeronautic communication systems from legacy users is vital due to stringent safety requirements and steady-state increase in air traffic. This paper proposes an L-band digital aeronautic communication systems receiver prototype that employs nonlinear operations to reduce the interference from the prime interference contributor distance measuring equipment. The knowledge of genie-aided estimator and optimum Bayesian estimator is utilized to propose improved and low complexity nonlinear devices, such as a genie-aided estimator enhanced pulse peak attenuator, genie-aided estimator enhanced pulse peak limiter, joint genie-aided estimator enhanced pulse peak attenuator, joint genie-aided estimator enhanced pulse peak limiter, optimum Bayesian estimator enhanced pulse peak attenuator, optimum Bayesian estimator enhanced pulse peak limiter, joint optimum Bayesian estimator enhanced pulse peak attenuator and joint optimum Bayesian estimator enhanced pulse peak limiter. The performance of the proposed methods is compared with the classical pulse blanking in terms of the received bit error rate for different signal-to-noise ratios. The proposed genie-aided estimator enhanced methods exhibited SNR saving in the range of 2 to 2.5 dB at a bit error rate of ${10}^{-1}$. At the same BER, the proposed optimum Bayesian estimator enhanced methods achieved SNR saving in the range of 2.5 to 3 dB. Full article