L-band Digital Aeronautical Communication System Research Articles

Impact Assessment of the L-Band Digital Aeronautical Communications System on the Joint Tactical Information Distribution System

The L-band digital aeronautical communications system (LDACS) is the future air–ground communications technology currently undergoing the International Civil Aviation Organization standardization process. As LDACS is intended to operate in the frequency band 960–1164 MHz, compatibility tests between LDACS and the legacy systems operating in this frequency band are necessary to ensure that no system is harmfully interfered. One of these systems is the joint tactical information distribution system (JTIDS), a technology employed by the tactical data link Link 16. In this paper, we present the results of an impact assessment of LDACS on JTIDS conducted through simulations. The extent of the impact has been quantified by simulating a wide variety of interference configurations, which are expected to cover most realistic interference conditions between LDACS and JTIDS. Baseband simulation models of both systems have been implemented and an interference scenario between LDACS and JTIDS has been defined. To evaluate the impact, the degradation of the signal-to-noise ratio (SNR) of JTIDS by the presence of LDACS has been determined. Default JTIDS transmissions, where the information is repeated at distant frequencies, do not show a significant degradation by the presence of strong LDACS interference, with an SNR loss lower than 1 dB in any considered interference scenario. Comparatively, a certain dependency on the specific LDACS deployment is noticeable for less protected JTIDS transmissions. Based on the observed interdependencies, recommendations for the deployment of LDACS are given in this paper, such that the impact of LDACS on JTIDS is minimized.

Gaussian Mixture Learning for LDPC Coded BICM Receivers With Blanking Nonlinearity

With the aid of blanking nonlinearity, the low density parity check (LDPC) coded bit-interleaved coded modulation (BICM) has been jointly considered as a robust mitigation for the impulsive interference in orthogonal frequency division multiplexing (OFDM) systems. However, the Gaussian assumption for the nonlinear channel conditional probability induces the mismatched L-values in the conventional MAP demodulator. In this paper, combined with the pulse blanking optimization via the PEXIT analysis, we propose a novel MAP demodulator based on the Gaussian mixture model (GMM) and estimate the parameters with the expectation-maximization (EM) algorithm. Taking the L-band Digital Aeronautical Communication System Type1 (L-DACS1) as an example, the GMM-based MAP demodulator can obtain the PEXIT thresholds that match the decoding curves well and provide the better BER performance in the interference-limit channel environment.

Feasibility of Cell Planning for the <italic>L</italic>-Band Digital Aeronautical Communications System Under the Constraint of Secondary Spectrum Usage

The L -band digital aeronautical communications system (LDACS) is a cellular air-ground data link for air traffic control. It is a cornerstone of the future aeronautical communications infrastructure. LDACS shall operate in the frequency band 960–1164 MHz under the constraint of secondary spectrum usage. This implies strict spectral, power, and spatial separation toward current legacy systems operating in this frequency band. It has been proposed to fulfil these restrictions using cell planning for LDACS without changing frequency allocations of the legacy systems. However, the feasibility of such a cell planning is yet to be demonstrated. In this paper, we demonstrate the feasibility of LDACS cell planning under these constraints. For this purpose, we introduce the theoretical limits for such a separation enabling the coexistence of LDACS and distance measuring equipment (DME: the primary user) system in the same frequency band. Closed-form expressions are obtained such that the proper operation of DME is not harmfully affected by LDACS. These expressions are utilized in the first step to find DME-compliant locations for LDACS ground stations. In the second step, interference constraints within LDACS itself are defined and applied. This approach yields DME-compliant locations of LDACS ground stations with channel assignments fulfilling the interference constraints. The application of our method shows that LDACS cell planning in Europe is possible without disturbing the proper operation of the DME system.

Efficient Spectrum Sensing for Aeronautical LDACS Using Low-Power Correlators

Air traffic has seen tremendous growth over the past decade pushing the need for enhanced air traffic management schemes. The $L$ -band digital aeronautical communication system (LDACS) is gaining traction as a scheme of choice, and aims to exploit the capabilities of modern digital communication techniques and computing architectures. Cognitive radio-based approaches have also been proposed for LDACS to improve spectrum efficiency and communication capacity; however, these require intelligent compute capability in aircrafts that enforce limited space and power budgets. This paper proposes the use of multiplierless correlation to enable spectrum sensing in LDACS air-to-ground links, and its integration into the on-board LDACS system. The proposed architecture offers improved performance over traditional energy detection (ED) even at low signal-to-noise ratio (SNR) with lower energy consumption than a multiplier-based correlator, while also assisting in receiver synchronization. We evaluate the proposed architecture on a Xilinx Zynq field-programmable gate array and show that our approach results in 28.3% reduction in energy consumption over the multiplier-based approach. Our results also show that the proposed architecture offers 100% accuracy in detection even at −12-dB SNR without requiring additional circuitry for noise estimation, which are an integral part of ED-based approaches.

Ambiguity Function Analysis for OFDM-Based LDACS Passive Multistatic Radar

The ambiguity function analysis is central to investigating the resolution capabilities of a radar system. It is particularly important for passive radar scenarios, where the signals of opportunity have not been originally designed for radar purposes. This paper focuses on studying the achievable resolution capabilities for a noncoherent orthogonal frequency division-multiplexing (OFDM)-based passive multistatic radar for L-band digital aeronautical communication system (LDACS) signals. For this purpose, the ambiguity function obtained when employing the OFDM-based LDACS communications signals as signals of opportunity is studied. A generic bistatic link is considered and closed-form expressions for the expectation of the corresponding ambiguity function when accounting for the different signal contributions are derived. The resulting expressions are then used to evaluate and analyze the overall multistatic radar ambiguity function for two sample radar scenarios. The results highlight the impact of the geometry on the shape of the ambiguity function, allowing therefore for a better understanding of the effect that the geometry has on the range and velocity resolution capabilities of the studied system.

Mitigation of DME interference in LDACS1-based future air-to-ground (A/G) communications

In this article, an algorithm for mitigating distance measuring equipment (DME) interference in L-band digital aeronautical communication system type 1 (LDACS1)-based aeronautical communication sys...

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.

Datalink security in the L-band digital aeronautical communications system (LDACS) for air traffic management

Today's very high-frequency (VHF) voice-based air–ground communication system for tactical aircraft guidance is suffering from the VHF band's increasing saturation in high-density areas [1]. The air–ground1 communication infrastructure is therefore undergoing modernization to ensure the sustainable growth of the European air transportation system in the coming decades [2], [3]. One major goal of this effort is the introduction of computerized air traffic management applications and new digital communication links between aircraft and ground systems.

Application of cognitive radio and interference cancellation in the L-Band based on future air-to-ground communication systems

The Very High Frequency band (VHF) currently used for aeronautical communications is becoming congested, and future Air-to-Ground (A/G) communication will require much greater use of data communications. For meeting future capacity requirements in aeronautical communications, we propose two new approaches one of which is a cognitive radio based A/G communication network that provides dynamic spectrum access to airplanes to overcome the spectrum scarcity problem in the VHF band. Another approach involves use of a new spectrum in the Ultra-High Frequency band (UHF) to create a new A/G link. In this paper, we propose and investigate the possibilities for developing a spectrum sensing approach to detect idle band in the VHF spectrum and analyze the possible interference between future L-band Digital Aeronautical Communication System (L-DACS) and legacy aeronautical systems.

OFDM Receiver Structure for a Subband-Selective Mitigation of Time-Variant Interference

System performance of orthogonal frequency-division multiplexing (OFDM) degrades in the presence of time-variant frequency-selective interference. In the literature, several pulse-blanking concepts have been introduced over the past few years, which are promising ways to mitigate impulsive interference for OFDM reception. However, blanking yields an attenuation of the signal and intercarrier interference (ICI). In this paper, a receiver structure is proposed, which consists of a frequency-selective pulse-blanking unit, a blanking mitigation unit, and an iterative ICI cancelation unit. The L-band Digital Aeronautical Communication System 1 (L-DACS 1) is regarded as an application that suffers from interference from the impulsive Distance Measuring Equipment (DME) system whose frequency bands partly overlap. It is shown that, by using the proposed mitigation scheme for impulsive interference, a reliable reception is possible, even in strong interference situations.

Cramér–Rao bounds for L‐band digital aeronautical communication system type 1 based passive multiple‐input multiple‐output radar

In this study, of concern is the achievable estimation accuracy for a non-coherent passive multiple-input multiple-output (MIMO) radar employing orthogonal frequency-division multiplexing (OFDM) based signals of opportunity. The motivation behind this investigation is the surveillance aspect of the air trac management modernisation process currently taking place in civil aviation. To this end, the surveillance capability of the OFDM-based L-band digital aeronautical communication system type 1 (LDACS1) is analysed. The extension of the LDACS1 communication system towards surveillance is of great importance since it would enable an alternative, non-cooperative surveillance application, and, together with the already validated navigation extension, establish a fully integrated LDACS1-based communication, navigation, and surveillance technology. The modied Cramer-Rao bound on the joint estimation of target location and velocity for a non-coherent passive MIMO radar, employing the OFDM-based LDACS1 signals as signals of opportunity, is investigated. The analysis is carried out assuming one target, multiple and widely separated transmit and receive antennas, orthogonal waveforms, independent reection coecients, and zero-mean white Gaussian noise. Closed-form expressions for the relevant elements of the modied Fisher information matrix are obtained. The results can be used to assess the estimation accuracy of a multiple antenna passive radar system employing any OFDM-based signals of opportunity.

Impulse interference mitigation method based on joint compressed sensing and whitening of interference

To mitigate the deleterious influence of distance measure equipment( DME) interference on orthogonal frequency division multiplexing( OFDM) receiver of L-band digital aeronautical communications system 1( L-DACS1) operating as an inlay system,a new DME interference suppression method was proposed based on joint compressed sensing and whitening of residual interference. Firstly,the DME impulse interference was observed via null subcarriers channel of the OFDM receiver and reconstructed with convex optimization constrained l1 norm minimization method based on the sparse property of the DME impulse interference in time domain. Then the reconstructed DME impulse interference was transformed to frequency domain and eliminated from the received signal. Finally,to avoid burst errors of demodulator,the residual impulse interference was converted to white Gaussian noise by using the de-interleaver and inverse orthogonal transformer.The computer simulation indicates that the proposed method can reduce the impact of DME interference effectively,and improve the reliability of OFDM receiver of the L-DACS1 system significantly.

LDACS: future aeronautical communications for air-traffic management

A major modernization process in air traffic management for civil aviation is currently taking place under the framework of SESAR and NextGen in Europe and the United States, respectively. Air traffic management modernization is required to meet the needs sustainable air traffic growth in Europe, the United States, and worldwide are posing. A key enabler for this modernization process is the introduction of improved communications, navigation, and surveillance technologies. In this article, new developments in aeronautical communications for air traffic management are presented, with special focus on the air/ground communications technology L-band Digital Aeronautical Communications System (LDACS). The most promising LDACS technology candidate, LDACS1, is described in detail, and possible extensions toward navigation and surveillance are discussed. With these extensions, LDACS1 is well placed to become the first integrated communications, navigation, and surveillance technology for civil aviation. Utilizing a common ground infrastructure, such an integrated approach simplifies deployment and reduces costs for both deployment and maintenance.

Overview of legacy systems in L-band and its influence on the future aeronautical communication system LDACS1

Currently, air traffc management is undergoing an extensive modernization process within SESAR [1] and Next-Gen [2] in Europe and the United States, respectively. This also includes the development of the future communication infrastructure (FCI) [3], which is jointly carried out by EUROCONTROL and the Federal Aviation Administration. Within the FCI, the L-band has been allocated for air-to-ground communications. Currently, two candidate systems for superseding the analogue voice communication system in the VHF band are taken into consideration. The frst candidate L-band digital aeronautical communications system type 1 (LDACS1) is a broadband system employing orthogonal frequency-division multiplexing (OFDM) and frequency-division duplex (FDD). LDACS1 has been designed as a combination of P34 (TIA 902 standard) and the broadband aeronautical multicarrier communications system [4]. The second candidate LDACS2 is a narrowband single-carrier system using time-division duplex as duplex scheme. This system is a derivative of the L-band digital link and the all-purpose multichannel aviation communication system.

On Improved Noise Variance Estimation for Aeronautical Communications

The L-band Digital Aeronautical Communication System Type-1 (L-DACS1) has been considered as the potential standard for future aeronautical communications. As an important parameter for L-DACS1, the noise variance can be estimated via the well known Second-Moment-Fourth-Moment (M2M4) blind algorithm. However, due to influence from aeronautical fading channels, performance degradation is encountered by conventional M2M4 algorithm in L-DACS1. In this paper, channel responses obtained from L-DACS1 pilot symbols were carried out to compensate the estimation degradation brought by channel fading, which lead to an improved M2M4 algorithm for L-DACS1. It is shown through simulations that the proposed approach outperforms conventional M2M4 estimator in terms of estimation error for L-DACS1 in aeronautical fading channels.

Survey on the Future Aeronautical Communication System and Its Development for Continental Communications

We present in this survey new technologies proposed for the evolution of the aeronautical communication infrastructure. Motivated by studies that estimate the growth of air traffic flow, it was decided to develop a future communication infrastructure (FCI) adapted to the future aeronautical scenario. The FCI development involves researchers, industrials, and aeronautical authorities from many countries around the world, and started in 2004. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the FCI that will be in charge of continental communication. The L-DACS is being developed in Europe since 2007 and two candidates were preselected: L-DACS1 and L-DACS2. In this paper, we first describe the motivations of the FCI. We then give an overview of its development activities from 2004 to 2009. After that, we provide some insights about both preselected L-DACS candidates, at their physical and medium access layers. Finally, we address the challenges on the development of the FCI/L-DACS.

Performance evaluation of network mobility handover over future aeronautical data link

The aviation community is currently working on the standardization of data communication systems for the future air traffic management. In this context, International Civil Aviation Organization (ICAO) has initiated a work on standardization of an IPv6-based aeronautical telecommunications network and on future radio access technologies, respectively. In this paper, we integrate L-Band Digital Aeronautical Communications System Option 1 (L-DACS 1), which is one candidate for future radio access technologies, with realistic IPv6-based network layer functionality and analyze the effect of handover delay to the TCP performance. Realistic Frame Error Rate (FER) values obtained from an L-DACS 1 physical layer simulator, which uses a realistic aeronautical channel model, are used in the simulation experiments. In the first stage, we decreased layer 3 handover latency by removing the Duplicate Address Detection (DAD) procedure for address configuration. In the second stage, we introduced a Home Agent (HA)-buffering method, which is used to buffer the traffic (destined to the mobile node) during handover. Transmission completion time is the primary performance metric in our analysis. With the HA-buffering method, the transmission completion time is reduced by at least 10% for the transmission of 110 kB of information over a wireless link with 31.5 kbit s −1 data rate.