Aeronautical Channel Research Articles

Moment-based modulation classification for Rician time-varying aeronautical channels

Modulation classification is a classical topic in the field of signal classification, and is of great significance in various applications including aeronautical communications. However, changes in the features of the signals transmitted through the Rician time-varying channels deteriorate the performance of modulation classification. In this study, a robust moment-based algorithm is proposed to counter the influence of the channels. The statistical correlation of the received samples are utilized for the estimation on the Rician factor. According to the derivation of the relationship between the moments of the transmitted samples and the received samples, the features utilized for classification are compensated mathematically. Finally, decision tree and random forest classifier are presented for classification. The estimation and classification performance of the proposed algorithm are analyzed for aeronautical en-route (EN) and arrival/takeoff (AT) channels through simulations. Meanwhile, real world signals of L-band digital aeronautical communication system (L-DACS1) are utilized for verification. The results show that our algorithm has high classification accuracy and low computational complexity.

Efficient Instantaneous Channel Propagation Modeling for Aeronautical Communications Systems With Compressed Sensing

Establishing an instantaneous channel propagation model in aircraft engineering simulators is important for aircraft systems development. This article investigates an instantaneous channel propagation modeling scheme with compressed sensing (CS) recovery and electromagnetic (EM) interpolation for aeronautical communications systems to reduce the cost of flight experiments. Specifically, the system architecture introduces the proposed modeling process of the instantaneous aeronautical channel. The mathematical models are analyzed to show the sparsity of the aeronautical channel with a limited scattering environment. The channel modeling algorithm is detailed by explaining the CS algorithm and the EM interpolation scheme. The experimental results show the effectiveness of the proposed method. Most recovery relative errors between the recovering channel model and the real sampled channel responses are lower than 0.1, i.e., −10 dB. More than 75% of the sampling points can be reduced by the proposed method compared with the real flight experiments. Moreover, the proposed single-input-single-output (SISO) approach can also be applied in the potential aeronautical communications systems with multiple-input-multiple-output (MIMO) transmission.

Efficient Channel Estimation for Aerial Wireless Communications

We present a technique to jointly estimate the channel taps and the frequency offset due to the Doppler effect of a special class of doubly dispersive aeronautical channels. The algorithm includes the use of pulse repetition techniques at the transmitter and the “power method” subspace iteration at the receiver. We show that transmitting constant-amplitude zero-autocorrelation sequences for channel sounding yields estimators with low computational complexity. Numerical simulations indicate performance comparable to the estimation-theoretic lower bound.

Aeronautical $Ad~Hoc$ Networking for the Internet-Above-the-Clouds

The engineering vision of relying on the ``smart sky" for supporting air traffic and the ``Internet above the clouds" for in-flight entertainment has become imperative for the future aircraft industry. Aeronautical ad hoc Networking (AANET) constitutes a compelling concept for providing broadband communications above clouds by extending the coverage of Air-to-Ground (A2G) networks to oceanic and remote airspace via autonomous and self-configured wireless networking amongst commercial passenger airplanes. The AANET concept may be viewed as a new member of the family of Mobile ad hoc Networks (MANETs) in action above the clouds. However, AANETs have more dynamic topologies, larger and more variable geographical network size, stricter security requirements and more hostile transmission conditions. These specific characteristics lead to more grave challenges in aircraft mobility modeling, aeronautical channel modeling and interference mitigation as well as in network scheduling and routing. This paper provides an overview of AANET solutions by characterizing the associated scenarios, requirements and challenges. Explicitly, the research addressing the key techniques of AANETs, such as their mobility models, network scheduling and routing, security and interference are reviewed. Furthermore, we also identify the remaining challenges associated with developing AANETs and present their prospective solutions as well as open issues. The design framework of AANETs and the key technical issues are investigated along with some recent research results. Furthermore, a range of performance metrics optimized in designing AANETs and a number of representative multi-objective optimization algorithms are outlined.

A Comprehensive Survey on UAV Communication Channel Modeling

Unmanned aerial vehicles (UAVs) have stroke great interested both by the academic community and the industrial community due to their diverse military applications and civilian applications. Furthermore, UAVs are also envisioned to be part of future airspace traffic. The application functions delivery relies on information exchange among UAVs as well as between UAVs and ground stations (GSs), which further closely depends on aeronautical channels. However, there is a paucity of comprehensive surveys on aeronautical channel modeling in line with the specific aeronautical characteristics and scenarios. To fill this gap, this paper focuses on reviewing the air-to-ground (A2G), ground-to-ground (G2G), and air-to-air (A2A) channel measurements and modeling for UAV communications and aeronautical communications under various scenarios. We also provide the design guideline for managing the link budget of UAV communications taking account of link losses and channel fading effects. Moreover, we also analyze the receive/transmit diversity gain and spatial multiplexing gain achieved by multiple-antenna-aided UAV communications. Finally, we discuss the remaining challenge and open issues for the future development of UAV communication channel modeling.

Regularized Zero-Forcing Precoding-Aided Adaptive Coding and Modulation for Large-Scale Antenna Array-Based Air-to-Air Communications

We propose a regularized zero-forcing transmit precoding (RZF-TPC)-aided and distance-based adaptive coding and modulation (ACM) scheme to support aeronautical communication applications, by exploiting the high spectral efficiency of the large-scale antenna arrays and link adaption. Our RZF-TPC-aided and distance-based ACM scheme switches its mode according to the distance between the communicating aircraft. We derive the closed-form asymptotic signal-to-interference-plus-noise ratio (SINR) expression of the RZF-TPC for the aeronautical channel, which is Rician, relying on a non-centered channel matrix that is dominated by the deterministic line-of-sight component. The effects of both realistic channel estimation errors and of the co-channel interference are considered in the derivation of this approximate closed-form SINR formula. Furthermore, we derive the analytical expression of the optimal regularization parameter that minimizes the mean square detection error. The achievable throughput expression based on our asymptotic approximate SINR formula is then utilized as the design metric for the proposed RZF-TPC-aided and distance-based ACM scheme. Monte-Carlo simulation results are presented for validating our theoretical analysis as well as for investigating the impact of the key system parameters. The simulation results closely match the theoretical results. In the specific example that two communicating aircrafts fly at a typical cruising speed of 920km/h, heading in opposite direction over the distance up to 740km taking a period of about 24 min, the RZF-TPC-aided and distance-based ACM is capable of transmitting a total of 77 GB of data with the aid of 64 transmit antennas and four receive antennas, which is significantly higher than that of our previous eigen-beamforming transmit precoding-aided and distance-based ACM benchmark.

Вплив завмирань Райса на роботу авіаційного супутникового OFDM каналу зв’язку

Мета: Метою цього дослідження є вивчення впливу райсівського завмирання на передачу повідомлень через авіаційний супутниковий OFDM канал з адаптивною модуляцією і розробка методу оцінки параметрів такого каналу. Методи дослідження: Вплив райсівського завмирання на передачу повідомлень через авіаційний супутниковий OFDM канал з адаптивною модуляцією вивчено за допомогою моделі каналу зв'язку "Літак - Супутник - Наземна станція", побудованої з використанням програмного пакету MATLAB Sіmulіnk. Модель включає в себе "Передавач літака", "Канали Вгору/Вниз", "Супутниковий транспондер" і "Приймач наземної станції". Кожен блок модулятора в банку модуляції виконує згортальне кодування з використанням кодових швидкостей ½, ²/3, ¾, і BPSK, QPSK, 16-QAM і 64-QAM модуляції. Результати: Отримано залежності SNR каналу від співвідношення між потужністю каналу прямої видимості й дифузного каналу, від посилення в каналі «Вниз» і затримки в дифузному каналі для різних типів доплерівського спектра і доплерівських зсувів частоти. Запропоновано метод оцінки параметрів супутникових каналів із завмиранням. Обговорення: Вперше розроблено реалістичну модель авіаційного супутникового OFDM каналу зв'язку з райсівськими завмираннями на основі стандарту IEEE 802.11a, яку використано для оцінки параметрів каналу. Запропонований в даній статті підхід можна розглядати як метод оцінки параметрів каналу з завмиранням.

Model of the Aeronautical Service Channel in the Meter and Decimeter Wavelength Bands for Adaptive Space Diversity Reception

We propose a model of the formation of signals generated by spaced diverse antennas operated in the meter and decimeter wavelength bands and used for the aeronautical service channel. This model is used to assess potential capabilities of spatial interference cancelers in a multi-beam aeronautical communication channel.

Doppler Mitigation in OFDM-Based Aeronautical Communications

Doppler spectrum in an aeronautical channel is modeled with dual-Doppler shift instead of classical Jakes model. Orthogonal frequency division multiplexing (OFDM)-based systems are sensitive to Doppler shifts/spread, since the time variation of the channel causes inter-carrier interference (ICI). ICI analysis is provided here for OFDM-based systems in the aeronautical channel. The effect of ICI on the received signal is presented and its power is derived. As compared with terrestrial channels, where ICI is generally overcome by increasing the subcarrier spacing and bounding the normalized Doppler frequency (NDF), we propose to mitigate the effect of Doppler shifts in aeronautical channels, as follows. First, we use parametric spectrum estimation methods to extract the Doppler shifts by exploiting the predictable number of paths. Then, a beamforming-based method is introduced to resolve the incoming rays by separating them individually. Finally, paths are Doppler-compensated and combined using diversity combining techniques. Computer simulations are performed to provide numerical results. It is shown that a mean square error (MSE) performance ofis achieved with the parametric estimation methods, and bit error rate (BER) performance approaching the no-Doppler scenario is obtained with the beamforming-based mitigation method.

Recognition of MQAM Signals in the Aeronautical Communication

For the complex recognition of signals in the aeronautical communication, the recognition of the star-type MQAM signals is studied under the aeronautical channel. The different scenarios of the aeronautical channel are analyzed and the reasonable channel model is established. The high order cumulant recognition algorithm which applies to the aeronautical channel is proposed, the invariant classification characteristics of modulation signals are constructed by this algorithm, and this algorithm is improved by using the receive diversity technique. Simulation results show that this algorithm significantly improves the correct recognition rate of the received signals has the good anti-fading and anti-noise performance and meets the requirements of the modulation recognition of MQAM signals under the aeronautical channel.

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.

Analysis of noise in aircraft cabins through the VHF channel

PurposeThe purpose of this paper is to present a method to analyze the noise in aircraft cabins through the VHF Aeronautical Communication Channel, aimed at examining an environment that has the possibility of communication problems between the aircraft crew and the professionals responsible for the controls on land.Design/methodology/approachThis analysis includes equipment normally used for identification and comparison of electromagnetic noise, the cabin and the environment that are present in an airport, as well as equipment for frequency analysis and intensity of those signals. The analysis is done in a reverse way, eliminating situations that are not common in the examined environment, until the identification of the situation with the irregularity.FindingsAccording to the results, the implementation of the Fourier transform for noise analysis in the cabin was efficient. These results demonstrate that through this transformation, the noise sources can be identified in the environments in cases where there is much spectrum pollution.Research limitations/implicationsThis kind of noise analysis is important, considering the importance of having good accuracy in airport environment analysis.Originality/valueThe paper presents the main trends in the future of aviation communications, and describes the new applications that aim to minimize problems with the current VHF channel.

A Method for the Analysis of the Aeronautical VHF Channel

This paper presents a method for the analysis of the Aeronautical VHF Channel, in order to analyze an environment with the possibility of problems in the communication between the crew of the aircraft and the professionals responsible for controls on land. This analysis includes equipment normally used for identification and comparison of noise environments present in an airport, as well as equipment for frequency and signal intensity analysis. The analysis is done in reverse, through the elimination of situations not considered as environmental features, enabling the identification of the irregular transmission. Given such a scenario, there are also presented the main trends in the future of aeronautical communications, demonstrating the new features that aim to minimize problems with the current Aeronautical VHF Channel. The final results demonstrate the possibility of identifying instances even without knowledge of the propagator environment.

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.

Analysis on characteristics of aeronautical wireless channels

In aeronautical mobile communication systems, wireless channels characteristics are different in scenarios of Parking, En-Route, Taxi, and Arrival/Take-off. By considering fading types, power spectrum density and delay characterization of aeronautical wireless channels, typical parameters of aeronautical wireless channels model are investigated to analyze characteristics of aeronautical wireless channels.

Multicarrier Communications Based on the Affine Fourier Transform in Doubly-Dispersive Channels

The affine Fourier transform (AFT), a general formulation of chirp transforms, has been recently proposed for use in multicarrier communications. The AFT-basedmulticarrier (AFT-MC) systemcan be considered as a generalization of the orthogonal frequency division multiplexing (OFDM), frequently used in modern wireless communications. AFT-MC keeps all important properties of OFDM and, in addition, gives a new degree of freedom in suppressing interference caused by Doppler spreading in time-varying multipath channels. We present a general interference analysis of the AFT-MC system that models both time and frequency dispersion effects. Upper and lower bounds on interference power are given, followed by interference power approximation that significantly simplifies interference analysis. The optimal parameters are obtained in the closed form followed by the analysis of the effects of synchronization errors and the optimal symbol period. A detailed interference analysis and optimal parameters are given for different aeronautical and land-mobile satellite (LMS) channel scenarios. It is shown that the AFT-MC system is able to match changes in these channels and efficiently reduce interference with high-spectral efficiency.

Performance Analysis of Different Phase Shift Keying Modulation Schemes in Aeronautical Channels

This paper undertakes the performance evaluation and comparison of different phase shift keying (PSK) modulation schemes in aeronautical channels. Specifically, bit error rate (BER) curves and outage probabilities of various modulation schemes in high dynamic environments are investigated by means of numerical analysis and computer simulation. Simulation results show that the performance of all modulation schemes degrades with the increase of the power ratio or dynamic factor, and that differential quadrature phase shift keying (DQPSK), differential 8 phase shift keying (D8PSK), 16 and 64 differential amplitude and phase shift keying (DAPSK) perform better than other same order modulation schemes, respectively. As the conclusion, the differential modulation schemes are more suitable for the aeronautical channels in order to withstand the Doppler shift and the changing rate of the Doppler.

Advances of aeronautical communications in the EU framework

AbstractThis paper reports on the advancement in the research and development of aeronautical satellite communications within the EU framework. Starting from key aspects such as spectrum regulatory and marketing issues which affect the development of aeronautical communication systems, discussion on the motivation behind the two EU projects, ABATE and WirelessCabin and their interconnection then follows. ABATE concentrated on the development of an aeronautical communications system for flight routes in the European and Northern Atlantic regions. The enabling technology considered in ABATE is discussed. Major achievements and results obtained in the project are reported in this paper. These include the development of a powerful software tool based on a logical design methodology for aeronautical satellite communication systems as well as the characterization of the aeronautical channel through a series of channel measurement campaign and a demonstration of in‐flight multimedia satellite communication. The evolvement from ABATE to WirelessCabin is then highlighted. The main objective and current development of WirelessCabin since the start of the project are presented. In particular, issues on electromagnetic compatibility between different electronic equipments on board the aircraft cabin are discussed. Networking aspects for mobility, QoS and VPN support are studied. Specifically, different scenarios for the location management and address assignment schemes for mobility and VPN support are discussed in detail. Copyright © 2004 John Wiley & Sons, Ltd.

Development and implementation of an advanced airport data link based on multi‐carrier communications

AbstractIn this paper, both the concept and the demonstrator implementation of an advanced airport data link is described which is used for data exchange between pilots and controllers in future surface movement guidance and control systems on airports. To fulfil future airport capacity requirements, the proposed data link has to be a high capacity, high rate data link. Therefore, the data link design is based on multi‐carrier code‐division multiple‐access which is a flexible and highly efficient multiple‐access transmission technique suitable for mobile communications in fading conditions. Both simulation results with typical aeronautical channel scenarios and bit error rate measurements using the demonstrator hardware show the suitability of multi‐carrier code‐division multiple‐access for aeronautical communications within the airport and its vicinity. Moreover, implementation effects which degrade the performance are identified and countermeasures are proposed and investigated. The results show that a reduction of the implementation loss of up to 2 dB is achievable by applying appropriate countermeasures.

Aeronautical channel modeling

A class of aeronautical wide-band channel models is proposed, featuring parking and taxi environments, takeoff and landing situations, and en-route scenarios for ground-air and air-air links. Typical and worst case parameter sets are suggested, based on published measurement results and empirical data. The models are suitable for channel emulators that can be easily implemented on digital computers or in hardware and thus are useful for the validation of digital aeronautical links. A time-domain and frequency-domain implementation of such a channel emulator are derived, and results for a typical multicarrier system are presented. It is shown that the scenarios have distinguishable performance results depending on the underlying maximum ranges and shapes of the Doppler and delay spectra and the presence of a line-of-sight path. Finally, the degrading effects of intersymbol interference and intersubcarrier interference on the multicarrier signal are explained.