Public perception of advanced aviation technologies: A review and roadmap to acceptance

The L-band digital aeronautical communications system (LDACS) is a key enabler of the new air traffic services and operational concepts necessary for the modernization of the air traffic management (ATM). After its initial design, compatibility tests with legacy L-band systems, and functional demonstrations in the laboratory, the system is currently undergoing the standardization process of the International Civil Aviation Organization (ICAO). However, LDACS has not been demonstrated in flight yet. In this article, we present the first in-flight demonstration of LDACS, which took place in March and April 2019 in southern Germany and included four LDACS ground stations and one LDACS airborne station. We detail the experimental setup of the implemented LDACS ground and airborne stations together with the flight routes, the conducted experiments, and the frequency planning to ensure compatibility with legacy systems. In addition, we describe the demonstrated ATM applications and the security measures used to protect them. Based on the obtained measurement results, we evaluate the LDACS in-flight communication performance for the first time, including the achieved communication range, the measured end-to-end message latency, and the LDACS capability to provide quality of service by effectively prioritizing safety-relevant data traffic. Furthermore, we use the in-flight received signal power to assess the applicability of a theoretical path loss model. These flight trials contribute to the final steps in the development of LDACS by providing its in-flight communication performance and by demonstrating: first, its correct functionality in a realistic environment; second, its capability of supporting ATM applications and the advanced security measures that can be used to protect them; and third, its spectrum compatibility with legacy systems. We conclude that LDACS is ready to support ATM operations and that LDACS frequency planning can safeguard legacy systems successfully.

/pdf/ldacs-flight-trials-demonstration-and-performance-analysis-3l0neqhsj0.pdf

LDACS Flight Trials: Demonstration and Performance Analysis of the Future Aeronautical Communications System

Markov Chain-Based Stochastic Modeling of Deep Signal Fading: Availability Assessment of Dual-Frequency GNSS-Based Aviation Under Ionospheric Scintillation

Future autonomous transportation is one of the most demanding application areas in terms of connectivity, as it has to simultaneously meet stringent criteria that do not typically go hand in hand, such as high throughput, low latency, high coverage/availability, high positioning and sensing accuracies, high security and robustness to interferences, etc. In order to meet the future demands of challenging applications, such as applications relying on autonomous vehicles, terrestrial networks are no longer sufficient and are to be augmented in the future with satellite-based networks. Among the emerging satellite networks, Low Earth Orbit (LEO) networks are able to provide advantages over traditional Medium Earth Orbit (MEO) and Geo-Stationary Earth Orbit (GEO) networks in terms of signal latency, cost, and performance. Nevertheless, several challenges exist in LEO system design, which have not been fully addressed in the existing literature. In particular, the problem of LEO-system optimization of design parameters is a multi-dimensional problem with many aspects to be considered. This paper offers a comprehensive survey of the LEO-system design parameters, of the challenges in LEO system design process, and of the optimization methods for satellite communication, positioning, and sensing applications, as well as a summarizing discussion on the design considerations for LEO-based networks to support future autonomous transportation.

https://www.mdpi.com/1424-8220/22/4/1421/pdf?version=1645603175

Survey on Optimization Methods for LEO-Satellite-Based Networks with Applications in Future Autonomous Transportation

Ground transportation systems demand accurate and robust localization functions Satellite navigation is considered a key element in those systems, but its position determination can be highly corrupted in urban environments because of the presence of reflected signals (ie multipath) This paper deals with the detection of multipath in the code measurements of GNSS receivers for mobile users in urban scenarios First, we discuss the different alternatives and limitations to properly isolate multipath autonomously at the receiver based on Code-Minus-Carrier (CMC) techniques in challenging GNSS applications We then propose a practical methodology to design a suitable multipath detector based on the time difference of CMC All the analysis and evaluations are supported with real measurements collected in Railway scenarios

/pdf/detection-of-gnss-multipath-with-time-differenced-code-minus-40mnlaisuc.pdf

Detection of GNSS Multipath with Time-Differenced Code-Minus-Carrier for Land-Based Applications

This paper presents the performance analysis of signals from the Galileo satellites in the E1 and E5a frequency bands and GPS L5 signals as measured by DLR’s experimental ground-based augmentation system. The results show that the raw noise and multipath level of Galileo signals and of the GPS L5 signals are smaller than that of GPS L1. The new signals are also less sensitive to the choice of carrier-smoothing time constant. Furthermore, the inter-frequency biases that affect dual-frequency processing are investigated. These biases differ between satellites and depend on satellite and receiver hardware, but they can be determined a priori. With known receiver and antenna configurations, it is possible to correct for these biases. A residual uncertainty associated with the bias correction has to be taken into account. This can be modeled as part of the ground and airborne bounding standard deviations (spr_gnd and spr_air) used in GBAS processing.

/pdf/evaluation-of-gps-l5-and-galileo-e1-and-e5a-performance-for-5ao16zetu1.pdf

Evaluation of GPS L5 and Galileo E1 and E5a Performance for Future Multifrequency and Multiconstellation GBAS

In the next generation of Ground Based Augmentation System (GBAS) corrections and integrity parameters for two frequencies and multiple constellations will be provided. However, the capacity of the VDB (VHF Data Broadcast) link providing those parameters to users is strongly limited. Thus providing all those new corrections and parameters would either require a longer update rate of corrections or a limitation on the number of satellites to which corrections are provided. In this paper we propose a new satellite selection method which allows fast selection of a variable sized, quasi-optimal subset of all visible GNSS satellites.

The proposed selection heuristic bases on a strong correlation between the third (i.e. vertical) component inside the S-matrix for each satellite and the probability of the related satellite being part of a subset which provides a favorable vertical protection level. Utilizing this correlation we design an algorithm which converges fast and leads to optimal results for a majority of constellations. As the selection can be performed for an arbitrary number of satellites and the complexity is not exponentially scaling with the number of available satellites, as an exhaustive search (brute-force) does, the heuristic is flexible and suitable for different applications even beyond GBAS’s.

In the context of GBAS these subsets still provide reliable protection levels as the contribution to the accuracy is dropping with every additional satellite. We show the feasibility of using for instance only 14 satellites in global protection level simulations. In a multi-frequency multi-constellation GBAS architecture the approach of selecting only an optimal subset allows to keep the current 2 Hz update rate. This could mitigate problems with VDB capacity or remove the necessity of additional, more frequent integrity messages.

/pdf/optimized-selection-of-satellite-subsets-for-a-multi-2q6xgv3ccx.pdf

Optimized Selection of Satellite Subsets for a Multi-Constellation GBAS

HorizonUAM: Safety and Security Considerations for Urban Air Mobility

With the new upcoming GNSS constellation in the future it
might no longer be possible to use all satellites in view for
navigation due to limited tracking channels. This is in particular
true in the context of Advanced Receiver Autonomous
Integrity Monitoring (ARAIM), where the use of dual frequency
is favorable to mitigate ionospheric disturbances.
To address the issues of limited channels we propose two
different satellites selection strategies adapted for Horizontal
ARAIM in this paper. First a bare geometric approach
which comes with almost no additional computation effort
at the cost of less stable results. And second a heuristic
optimization which improves selection results significantly
while adding additional computational effort.
Both approaches are compared to brute force selected best
sets in terms of resulting protection levels, computational
cost and achieved ARAIM availability.
Results show the general applicability of both presented
selection methods in Horizontal ARAIM. Using limited sets
instead of all satellites in view can still provide global availability.
Depending on the method more or less satellites are
necessary to ensure sufficiently small and stable protection
levels.

/pdf/satellite-selection-methodology-for-horizontal-navigation-3xntx3zeqt.pdf

Satellite Selection Methodology for Horizontal Navigation and Integrity Algorithms

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