68 research outputs found
Grid-based Hybrid 3DMA GNSS and Terrestrial Positioning
The paper discusses the increasing use of hybridized sensor information for
GNSS-based localization and navigation, including the use of 3D map-aided GNSS
positioning and terrestrial systems based on different geometric measurement
principles. However, both GNSS and terrestrial systems are subject to negative
impacts from the propagation environment, which can violate the assumptions of
conventionally applied parametric state estimators. Furthermore, dynamic
parametric state estimation does not account for multi-modalities within the
state space leading to an information loss within the prediction step. In
addition, the synchronization of non-deterministic multi-rate measurement
systems needs to be accounted.
In order to address these challenges, the paper proposes the use of a
non-parametric filtering method, specifically a 3DMA multi-epoch Grid Filter,
for the tight integration of GNSS and terrestrial signals. Specifically, the
fusion of GNSS, Ultra-wide Band (UWB) and vehicle motion data is introduced
based on a discrete state representation. Algorithmic challenges, including the
use of different measurement models and time synchronization, are addressed. In
order to evaluate the proposed method, real-world tests were conducted on an
urban automotive testbed in both static and dynamic scenarios.
We empirically show that we achieve sub-meter accuracy in the static scenario
by averaging a positioning error of m, whereas in the dynamic scenario
the average positioning error amounts to m.
The paper provides a proof-of-concept of the introduced method and shows the
feasibility of the inclusion of terrestrial signals in a 3DMA positioning
framework in order to further enhance localization in GNSS-degraded
environments
Potentials of Deterministic Radio Propagation Simulation for AI-Enabled Localization and Sensing
Machine leaning (ML) and artificial intelligence (AI) enable new methods for
localization and sensing in next-generation networks to fulfill a wide range of
use cases. These approaches rely on learning approaches that require large
amounts of training and validation data. This paper addresses the data
generation bottleneck to develop and validate such methods by proposing an
integrated toolchain based on deterministic channel modeling and radio
propagation simulation. The toolchain is demonstrated exemplary for scenario
classification to obtain localization-related channel parameters within an
aircraft cabin environment
An Empirical Study on V2X Enhanced Low-Cost GNSS Cooperative Positioning in Urban Environments
High-precision and lane selective position estimation is of fundamental importance for prospective advanced driver assistance systems (ADAS) and automated driving functions, as well as for traffic information and management processes in intelligent transportation systems (ITS). User and vehicle positioning is usually based on Global Navigation Satellite System (GNSS), which, as stand-alone positioning, does not meet the necessary requirements in terms of accuracy. Furthermore, the rise of connected driving offers various possibilities to enhance GNSS positioning by applying cooperative positioning (CP) methods. Utilizing only low-cost sensors, especially in urban environments, GNSS CP faces several demanding challenges. Therefore, this contribution presents an empirical study on how Vehicle-to-Everything (V2X) technologies can aid GNSS position estimation in urban environments, with the focus being solely on positioning performance instead of multi-sensor data fusion. The performance of CP utilizing common positioning approaches as well as CP integration in state-of-the-art Vehicular Ad-hoc Networks (VANET) is displayed and discussed. Additionally, a measurement campaign, providing a representational foundation for validating multiple CP methods using only consumer level and low-cost GNSS receivers, as well as commercially available IEEE 802.11p V2X communication modules in a typical urban environment is presented. Evaluating the algorithm&rsquo
s performance, it is shown that CP approaches are less accurate compared to single positioning in the given environment. In order to investigate error influences, a skyview modelling seeking to identify non-line-of-sight (NLoS) effects using a 3D building model was performed. We found the position estimates to be less accurate in areas which are affected by NLoS effects such as multipath reception. Due to covariance propagation, the accuracy of CP approaches is decreased, calling for strategies for multipath detection and mitigation. In summary, this contribution will provide insights on integration, implementation strategies and accuracy performances, as well as drawbacks for local area, low-cost GNSS CP in urban environments.
Document type: Articl
Quantum Nature of Light Measured With a Single Detector
We realized the most fundamental quantum optical experiment to prove the
non-classical character of light: Only a single quantum emitter and a single
superconducting nanowire detector were used. A particular appeal of our
experiment is its elegance and simplicity. Yet its results unambiguously
enforce a quantum theory for light. Previous experiments relied on more complex
setups, such as the Hanbury-Brown-Twiss configuration, where a beam splitter
directs light to two photodetectors, giving the false impression that the beam
splitter is required. Our work results in a major simplification of the widely
used photon-correlation techniques with applications ranging from quantum
information processing to single-molecule detection.Comment: 7 page
Mechanical behavior and size effects of polymer/amorphous NiB composites with 3D micro‐ architectures
Micro-architectured materials are a new class of hierarchical cellular material with outstanding properties. By designing advantageous cellular geometries and combining the material size effects at the nanometer scale, lightweight hybrid micro-architectured materials with hierarchical cellular structures and tailored structural properties are achieved. Previous papers have reported the mechanical properties of ceramic/polymer composites but few studies have examined the properties of similar structures with metal coatings instead of ceramic. To estimate the mechanical performance of polymer cellular structure reinforced with a metal coating, we combined 3D laser lithography and electroless deposition of an amorphous layer of NiB to produce metal/polymer hybrid structures. In this poster, the fabrication of 3D hybrid structures by electroless deposition aiming at achieving high and yet low density material will be presented. We also studied the mechanical response of micro-architectured structures as a function of the architecture design and the thickness of the amorphous NiB layer on their deformation mechanisms. In situ SEM microcompression experiments revealed a change in the deformation behavior with the NiB layer thickness, suggesting that the deformation mechanism and the buckling behavior are controlled by the size induced brittle-to-ductile transition in the NiB layer. In addition, the energy absorption properties demonstrate the possibility of tuning the energy absorption efficiency with adequate designs.
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Toward UWB Impulse Radio Sensing: Fundamentals, Potentials, and Challenges
Radio sensing is a rapidly emerging research field. It focuses on designing an integrated communication system that can also perform localization and radar functionalities sharing the same transmit signals and potentially the same hardware. Ultra-wideband (UWB) impulse radio is a promising technology for radio sensing because it offers a high-range resolution and direct access to the channel impulse response (CIR) to observe the multipath components (MPCs) of the wideband channel caused by scattering at target objects. This approach enables a wide range of functionalities and applications, especially in the field of mobility and transportation. The foundation is given by the signal propagation and channel modeling of the UWB channel, which is briefly revisited in this chapter. Based on the CIR and estimated MPCs the target object can be localized like a multistatic passive radar. The influence of geometry in a passive target localization system is studied by calculating the geometric dilution of precision (GDOP). In addition to passive localization more tasks and functionalities of radio sensing, are briefly introduced including detection, tracking, imaging, counting, and classification. The chapter concludes with further research directions and challenges in UWB radio sensing, especially for real-world use in the context of mobility applications
Extending Quantum Links: Modules for Fiber- and Memory-Based Quantum Repeaters
We analyze elementary building blocks for quantum repeaters based on fiber
channels and memory stations. Implementations are considered for three
different physical platforms, for which suitable components are available:
quantum dots, trapped atoms and ions, and color centers in diamond. We evaluate
and compare the performances of basic quantum repeater links for these
platforms both for present-day, state-of-the-art experimental parameters as
well as for parameters that could in principle be reached in the future. The
ultimate goal is to experimentally explore regimes at intermediate distances,
up to a few 100 km, in which the repeater-assisted secret key transmission
rates exceed the maximal rate achievable via direct transmission. We consider
two different protocols, one of which is better adapted to the higher source
clock rate and lower memory coherence time of the quantum dot platform, while
the other circumvents the need of writing photonic quantum states into the
memories in a heralded, non-destructive fashion. The elementary building blocks
and protocols can be connected in a modular form to construct a quantum
repeater system that is potentially scalable to large distances.Comment: 48 pages in Word style, "White Paper" of Q.Link.X Consortiu
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Quantum dot-based broadband optical antenna for efficient extraction of single photons in the telecom O-band
Long-distance fiber-based quantum communication relies on efficient non-classical light sources operating at telecommunication wavelengths. Semiconductor quantum dots are promising candidates for on-demand generation of single photons and entangled photon pairs for such applications. However, their brightness is strongly limited due to total internal reflection at the semiconductor/vacuum interface. Here we overcome this limitation using a dielectric antenna structure. The non-classical light source consists of a gallium phosphide solid immersion lens in combination with a quantum dot nanomembrane emitting single photons in the telecom O-band. With this device, the photon extraction is strongly increased in a broad spectral range. A brightness of 17% (numerical aperture of 0.6) is obtained experimentally, with a single photon purity of (2)(0)=0.049±0.02 at saturation power. This brings the practical implementation of quantum communication networks one step closer
Quantum Transduction of Telecommunications-band Single Photons from a Quantum Dot by Frequency Upconversion
The ability to transduce non-classical states of light from one wavelength to
another is a requirement for integrating disparate quantum systems that take
advantage of telecommunications-band photons for optical fiber transmission of
quantum information and near-visible, stationary systems for manipulation and
storage. In addition, transducing a single-photon source at 1.3 {\mu}m to
visible wavelengths for detection would be integral to linear optical quantum
computation due to the challenges of detection in the near-infrared. Recently,
transduction at single-photon power levels has been accomplished through
frequency upconversion, but it has yet to be demonstrated for a true
single-photon source. Here, we transduce the triggered single-photon emission
of a semiconductor quantum dot at 1.3 {\mu}m to 710 nm with a total detection
(internal conversion) efficiency of 21% (75%). We demonstrate that the 710 nm
signal maintains the quantum character of the 1.3 {\mu}m signal, yielding a
photon anti-bunched second-order intensity correlation, g^(2)(t), that shows
the optical field is composed of single photons with g^(2)(0) = 0.165 < 0.5.Comment: 7 pages, 4 figure
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