173 research outputs found
Compressive Sensing of Multiband Spectrum towards Real-World Wideband Applications.
PhD Theses.Spectrum scarcity is a major challenge in wireless communication systems with their
rapid evolutions towards more capacity and bandwidth. The fact that the real-world
spectrum, as a nite resource, is sparsely utilized in certain bands spurs the proposal
of spectrum sharing. In wideband scenarios, accurate real-time spectrum sensing, as an
enabler of spectrum sharing, can become ine cient as it naturally requires the sampling
rate of the analog-to-digital conversion to exceed the Nyquist rate, which is resourcecostly
and energy-consuming. Compressive sensing techniques have been applied in
wideband spectrum sensing to achieve sub-Nyquist-rate sampling of frequency sparse
signals to alleviate such burdens.
A major challenge of compressive spectrum sensing (CSS) is the complexity of the sparse
recovery algorithm. Greedy algorithms achieve sparse recovery with low complexity but
the required prior knowledge of the signal sparsity. A practical spectrum sparsity estimation
scheme is proposed. Furthermore, the dimension of the sparse recovery problem
is proposed to be reduced, which further reduces the complexity and achieves signal
denoising that promotes recovery delity. The robust detection of incumbent radio is
also a fundamental problem of CSS. To address the energy detection problem in CSS,
the spectrum statistics of the recovered signals are investigated and a practical threshold
adaption scheme for energy detection is proposed. Moreover, it is of particular interest to
seek the challenges and opportunities to implement real-world CSS for systems with large
bandwidth. Initial research on the practical issues towards the real-world realization of
wideband CSS system based on the multicoset sampler architecture is presented.
In all, this thesis provides insights into two critical challenges - low-complexity sparse
recovery and robust energy detection - in the general CSS context, while also looks
into some particular issues towards the real-world CSS implementation based on the
i
multicoset sampler
Topological triply-degenerate point with double Fermi arcs
Unconventional chiral particles have recently been predicted to appear in
certain three dimensional (3D) crystal structures containing three- or
more-fold linear band degeneracy points (BDPs). These BDPs carry topological
charges, but are distinct from the standard twofold Weyl points or fourfold
Dirac points, and cannot be described in terms of an emergent relativistic
field theory. Here, we report on the experimental observation of a topological
threefold BDP in a 3D phononic crystal. Using direct acoustic field mapping, we
demonstrate the existence of the threefold BDP in the bulk bandstructure, as
well as doubled Fermi arcs of surface states consistent with a topological
charge of 2. Another novel BDP, similar to a Dirac point but carrying nonzero
topological charge, is connected to the threefold BDP via the doubled Fermi
arcs. These findings pave the way to using these unconventional particles for
exploring new emergent physical phenomena
EmotionGesture: Audio-Driven Diverse Emotional Co-Speech 3D Gesture Generation
Generating vivid and diverse 3D co-speech gestures is crucial for various
applications in animating virtual avatars. While most existing methods can
generate gestures from audio directly, they usually overlook that emotion is
one of the key factors of authentic co-speech gesture generation. In this work,
we propose EmotionGesture, a novel framework for synthesizing vivid and diverse
emotional co-speech 3D gestures from audio. Considering emotion is often
entangled with the rhythmic beat in speech audio, we first develop an
Emotion-Beat Mining module (EBM) to extract the emotion and audio beat features
as well as model their correlation via a transcript-based visual-rhythm
alignment. Then, we propose an initial pose based Spatial-Temporal Prompter
(STP) to generate future gestures from the given initial poses. STP effectively
models the spatial-temporal correlations between the initial poses and the
future gestures, thus producing the spatial-temporal coherent pose prompt. Once
we obtain pose prompts, emotion, and audio beat features, we will generate 3D
co-speech gestures through a transformer architecture. However, considering the
poses of existing datasets often contain jittering effects, this would lead to
generating unstable gestures. To address this issue, we propose an effective
objective function, dubbed Motion-Smooth Loss. Specifically, we model motion
offset to compensate for jittering ground-truth by forcing gestures to be
smooth. Last, we present an emotion-conditioned VAE to sample emotion features,
enabling us to generate diverse emotional results. Extensive experiments
demonstrate that our framework outperforms the state-of-the-art, achieving
vivid and diverse emotional co-speech 3D gestures.Comment: Under revie
Topology Design for Data Center Networks Using Deep Reinforcement Learning
This paper is concerned with the topology design of data center networks (DCNs) for low latency and fewer links using deep reinforcement learning (DRL). Starting from a Kvertex-connected graph, we propose an interactive framework with single-objective and multi-objective DRL agents to learn DCN topologies for given node traffic matrices by choosing link matrices to represent the states and actions as well as using the average shortest path length together with action penalty terms as reward feedback. Comparisons with commonly used DCN topologies are given to show the effectiveness and merits of our method. The results reveal that our learned topologies could achieve lower delay compared with common DCN topologies. Moreover, we believe that the method can be extended to other topology metrics, e.g., throughput, by simply modifying the reward functions
Pulse shape discrimination based on the Tempotron: a powerful classifier on GPU
This study introduces the Tempotron, a powerful classifier based on a
third-generation neural network model, for pulse shape discrimination. By
eliminating the need for manual feature extraction, the Tempotron model can
process pulse signals directly, generating discrimination results based on
learned prior knowledge. The study performed experiments using GPU
acceleration, resulting in over a 500 times speedup compared to the CPU-based
model, and investigated the impact of noise augmentation on the Tempotron's
performance. Experimental results showed that the Tempotron is a potent
classifier capable of achieving high discrimination accuracy. Furthermore,
analyzing the neural activity of Tempotron during training shed light on its
learning characteristics and aided in selecting the Tempotron's
hyperparameters. The dataset used in this study and the source code of the
GPU-based Tempotron are publicly available on GitHub at
https://github.com/HaoranLiu507/TempotronGPU.Comment: 14 pages,7 figure
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