41 research outputs found
Estimation of Signal Parameters using Deep Convolutional Neural Networks
This paper introduces a Deep Learning approach for signal parameter
estimation in the context of wireless channel modeling. Our work is capable of
multidimensional parameter estimation from a signal containing an unknown
number of paths. The signal parameters are estimated relative to a predefined
grid, providing quasi grid-free, hence, more accurate estimates than previous
grid-limited approaches. It requires no prior knowledge of the number of paths,
giving it an advantage in terms of complexity compared to existing solutions.
Along with the description, we provide an initial performance analysis and a
comparison with State-of-the-Art techniques and discuss future research
directions
Measurement Testbed for Radar and Emitter Localization of UAV at 3.75 GHz
This paper presents an experimental measurement platform for the research and
development of unmanned aerial vehicles (UAVs) localization algorithms using
radio emission and reflectivity. We propose a cost-effective, flexible testbed
made from commercial off-the-shelf (COTS) devices to allow academic research
regarding the upcoming integration of UAV surveillance in existing mobile radio
networks in terms of integrated sensing and communication (ISAC). The system
enables nanosecond-level synchronization accuracy and centimeter-level
positioning accuracy for multiple distributed sensor nodes and a mobile
UAV-mounted node. Results from a real-world measurement in a 16 km2 urban area
demonstrate the system's performance with both emitter localization as well as
with the radar setup
Budding transitions of fluid-bilayer vesicles: the effect of area-difference elasticity
Budding and vesiculation are prominent shape transformations of fluid lipid-bilayer vesicles. We discuss these transitions within the context of a curvature model which contains two types of bending energy. In addition to the usual local curvature elasticity κ, we include the effect of a relative areal stretching of the two monolayers. This area-difference elasticity leads to an effective nonlocal curvature energy characterized by another parameter κ¯. We argue that the two contributions to the curvature energy are typically comparable in magnitude. The model interpolates smoothly between the spontaneous-curvature model (κ¯=0) and the bilayer-couple model (κ¯→∞), discussed previously in the literature. Conceptually, this model is not new; however, neither its consequences nor its relation to experiment has previously been explored in detail. In particular, budding is discontinuous (first order) for small κ¯ but changes via a tricritical point to continuous (second order) for large κ¯. The order of the budding transition depends on both the ratio κ¯/κ (which is a material parameter) and the initial area difference between the inner and outer monolayers (which can be modified by appropriate treatment of the vesicle). Estimates suggest that, under typical laboratory conditions, the budding process should be discontinuous, in apparent disagreement with some recent experiments. Possible reasons for this discrepancy are discussed. We propose, in particular, that hysteretic effects are important and that the observed behavior may reflect a spinodal instability
Periodic Lamellipodial Contractions Correlate with Rearward Actin Waves
AbstractCellular lamellipodia bind to the matrix and probe its rigidity through forces generated by rearward F-actin transport. Cells respond to matrix rigidity by moving toward more rigid matrices using an unknown mechanism. In spreading and migrating cells we find local periodic contractions of lamellipodia that depend on matrix rigidity, fibronectin binding and myosin light chain kinase (MLCK). These contractions leave periodic rows of matrix bound β3-integrin and paxillin while generating waves of rearward moving actin bound α-actinin and MLCK. The period between contractions corresponds to the time for F-actin to move across the lamellipodia. Shortening lamellipodial width by activating cofilin decreased this period proportionally. Increasing lamellipodial width by Rac signaling activation increased this period. We propose that an actin bound, contraction-activated signaling complex is transported locally from the tip to the base of the lamellipodium, activating the next contraction/extension cycle
Dynamic Phase Transitions in Cell Spreading
We monitored isotropic spreading of mouse embryonic fibroblasts on
fibronectin-coated substrates. Cell adhesion area versus time was measured via
total internal reflection fluorescence microscopy. Spreading proceeds in
well-defined phases. We found a power-law area growth with distinct exponents
a_i in three sequential phases, which we denote basal (a_1=0.4+-0.2), continous
(a_2=1.6+-0.9) and contractile (a_3=0.3+-0.2) spreading. High resolution
differential interference contrast microscopy was used to characterize local
membrane dynamics at the spreading front. Fourier power spectra of membrane
velocity reveal the sudden development of periodic membrane retractions at the
transition from continous to contractile spreading. We propose that the
classification of cell spreading into phases with distinct functional
characteristics and protein activity patterns serves as a paradigm for a
general program of a phase classification of cellular phenotype. Biological
variability is drastically reduced when only the corresponding phases are used
for comparison across species/different cell lines.Comment: 4 pages, 5 figure
Cooperative Passive Coherent Location: A Promising 5G Service to Support Road Safety
5G promises many new vertical service areas beyond simple communication and
data transfer. We propose CPCL (cooperative passive coherent location), a
distributed MIMO radar service, which can be offered by mobile radio network
operators as a service for public user groups. CPCL comes as an inherent part
of the radio network and takes advantage of the most important key features
proposed for 5G. It extends the well-known idea of passive radar (also known as
passive coherent location, PCL) by introducing cooperative principles. These
range from cooperative, synchronous radio signaling, and MAC up to radar data
fusion on sensor and scenario levels. By using software-defined radio and
network paradigms, as well as real-time mobile edge computing facilities
intended for 5G, CPCL promises to become a ubiquitous radar service which may
be adaptive, reconfigurable, and perhaps cognitive. As CPCL makes double use of
radio resources (both in terms of frequency bands and hardware), it can be
considered a green technology. Although we introduce the CPCL idea from the
viewpoint of vehicle-to-vehicle/infrastructure (V2X) communication, it can
definitely also be applied to many other applications in industry, transport,
logistics, and for safety and security applications
Endoplasmic spreading requires coalescence of vimentin intermediate filaments at force-bearing adhesions
10.1091/mbc.E12-05-0377Molecular Biology of the Cell24121-30MBCE
eadf: representation of far-field antenna responses in Python
Understanding and analysis of antennas is crucial for the development of modern telecommunication technologies, like 5G or massive MIMO. Research in this area has the need for software to measure, analyze and test antenna systems. For instance, one needs a convenient way to transform large amounts of antenna measurement data into a concise representation. The herein described eadf package aims at providing this functionality. On top of that, it offers routines to interpolate the beam-pattern of an antenna as well as compressing it in spatial frequency domain. As such, it can be used for the development of high resolution parameter estimation algorithms and analysis of antenna beam-patterns. In summary, the package provides a flexible and extensible framework for dealing with antennas
Improving the Spatial Correlation Characteristics of Antenna Arrays using Linear Operators and Wide-band Modelling
The analysis of wireless communication channels at the mmWave, sub-THz and
THz bands gives rise to difficulties in the construction of antenna arrays due
to the small maximum inter-element spacing constraints at these frequencies.
Arrays with uniform spacing greater than half the wavelength for a certain
carrier frequency exhibit aliasing side-lobes in the angular domain,
prohibiting non-ambiguous estimates of a propagating wave-front's angle of
arrival.
In this paper, we present how wide-band modelling of the array response is
useful in mitigating this spatial aliasing effect. This approach aims to reduce
the grating lobes by exploiting the angle- and frequency-dependent phase-shifts
observed in the response of the array to a planar wave-front travelling across
it.
Furthermore, we propose a method by which the spatial correlation
characteristics of an array operating at 33 GHz carrier frequency with an
instantaneous bandwidth of 1 GHz can be improved such that the angular-domain
side-lobes are reduced by 5-10 dB. This method, applicable to arbitrary antenna
array manifolds, makes use of a linear operator that is applied to the
base-band samples of the channel transfer function measured in space and
frequency domains. By means of synthetically simulated arrays, we show that
when operating with a bandwidth of 1 GHz, the use of a derived linear operator
applied to the array output results in the spatial correlation characteristics
approaching those of the array operating at a bandwidth of 12 GHz. Hence,
non-ambiguous angle estimates can be obtained in the field without the use of
expensive high-bandwidth RF front-end components.Comment: 7 pages, 4 figures, 27th Workshop on Smart Antennas, 202