4,898 research outputs found
Energy Efficient User Association and Power Allocation in Millimeter Wave Based Ultra Dense Networks with Energy Harvesting Base Stations
Millimeter wave (mmWave) communication technologies have recently emerged as
an attractive solution to meet the exponentially increasing demand on mobile
data traffic. Moreover, ultra dense networks (UDNs) combined with mmWave
technology are expected to increase both energy efficiency and spectral
efficiency. In this paper, user association and power allocation in mmWave
based UDNs is considered with attention to load balance constraints, energy
harvesting by base stations, user quality of service requirements, energy
efficiency, and cross-tier interference limits. The joint user association and
power optimization problem is modeled as a mixed-integer programming problem,
which is then transformed into a convex optimization problem by relaxing the
user association indicator and solved by Lagrangian dual decomposition. An
iterative gradient user association and power allocation algorithm is proposed
and shown to converge rapidly to an optimal point. The complexity of the
proposed algorithm is analyzed and the effectiveness of the proposed scheme
compared with existing methods is verified by simulations.Comment: to appear, IEEE Journal on Selected Areas in Communications, 201
Rate-Splitting for Intelligent Reflecting Surface-Aided Multiuser VR Streaming
The growing demand for virtual reality (VR) applications requires wireless
systems to provide a high transmission rate to support 360-degree video
streaming to multiple users simultaneously. In this paper, we propose an
intelligent reflecting surface (IRS)-aided rate-splitting (RS) VR streaming
system. In the proposed system, RS facilitates the exploitation of the shared
interests of the users in VR streaming, and IRS creates additional propagation
channels to support the transmission of high-resolution 360-degree videos. IRS
also enhances the capability to mitigate the performance bottleneck caused by
the requirement that all RS users have to be able to decode the common message.
We formulate an optimization problem for maximization of the achievable bitrate
of the 360-degree video subject to the quality-of-service (QoS) constraints of
the users. We propose a deep deterministic policy gradient with imitation
learning (Deep-GRAIL) algorithm, in which we leverage deep reinforcement
learning (DRL) and the hidden convexity of the formulated problem to optimize
the IRS phase shifts, RS parameters, beamforming vectors, and bitrate selection
of the 360-degree video tiles. We also propose RavNet, which is a deep neural
network customized for the policy learning in our Deep-GRAIL algorithm.
Performance evaluation based on a real-world VR streaming dataset shows that
the proposed IRS-aided RS VR streaming system outperforms several baseline
schemes in terms of system sum-rate, achievable bitrate of the 360-degree
videos, and online execution runtime. Our results also reveal the respective
performance gains obtained from RS and IRS for improving the QoS in multiuser
VR streaming systems.Comment: 20 pages, 12 figures. This paper has been submitted to IEEE journal
for possible publicatio
Word matching using single closed contours for indexing handwritten historical documents
Effective indexing is crucial for providing convenient access to scanned versions of large collections of historically valuable handwritten manuscripts. Since traditional handwriting recognizers based on optical character recognition (OCR) do not perform well on historical documents, recently a holistic word recognition approach has gained in popularity as an attractive and more straightforward solution (Lavrenko et al. in proc. document Image Analysis for Libraries (DIALâ04), pp. 278â287, 2004). Such techniques attempt to recognize words based on scalar and profile-based features extracted from whole word images. In this paper, we propose a new approach to holistic word recognition for historical handwritten manuscripts based on matching word contours instead of whole images or word profiles. The new method consists of robust extraction of closed word contours and the application of an elastic contour matching technique proposed originally for general shapes (Adamek and OâConnor in IEEE Trans Circuits Syst Video Technol 5:2004). We demonstrate that multiscale contour-based descriptors can effectively capture intrinsic word features avoiding any segmentation of words into smaller subunits. Our experiments show a recognition accuracy of 83%, which considerably exceeds the performance of other systems reported in the literature
Rethinking Motor Learning and Savings in Adaptation Paradigms: Model-Free Memory for Successful Actions Combines with Internal Models
SummaryAlthough motor learning is likely to involve multiple processes, phenomena observed in error-based motor learning paradigms tend to be conceptualized in terms of only a single process: adaptation, which occurs through updating an internal model. Here we argue that fundamental phenomena like movement direction biases, savings (faster relearning), and interference do not relate to adaptation but instead are attributable to two additional learning processes that can be characterized as model-free: use-dependent plasticity and operant reinforcement. Although usually âhiddenâ behind adaptation, we demonstrate, with modified visuomotor rotation paradigms, that these distinct model-based and model-free processes combine to learn an error-based motor task. (1) Adaptation of an internal model channels movements toward successful error reduction in visual space. (2) Repetition of the newly adapted movement induces directional biases toward the repeated movement. (3) Operant reinforcement through association of the adapted movement with successful error reduction is responsible for savings
High-dimensional structure estimation in Ising models: Local separation criterion
We consider the problem of high-dimensional Ising (graphical) model
selection. We propose a simple algorithm for structure estimation based on the
thresholding of the empirical conditional variation distances. We introduce a
novel criterion for tractable graph families, where this method is efficient,
based on the presence of sparse local separators between node pairs in the
underlying graph. For such graphs, the proposed algorithm has a sample
complexity of , where is the number of
variables, and is the minimum (absolute) edge potential in the
model. We also establish nonasymptotic necessary and sufficient conditions for
structure estimation.Comment: Published in at http://dx.doi.org/10.1214/12-AOS1009 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Control of RelB during dendritic cell activation integrates canonical and noncanonical NF-ÎșB pathways.
The NF-ÎșB protein RelB controls dendritic cell (DC) maturation and may be targeted therapeutically to manipulate T cell responses in disease. Here we report that RelB promoted DC activation not as the expected RelB-p52 effector of the noncanonical NF-ÎșB pathway, but as a RelB-p50 dimer regulated by canonical IÎșBs, IÎșBα and IÎșBÉ. IÎșB control of RelB minimized spontaneous maturation but enabled rapid pathogen-responsive maturation. Computational modeling of the NF-ÎșB signaling module identified control points of this unexpected cell type-specific regulation. Fibroblasts that we engineered accordingly showed DC-like RelB control. Canonical pathway control of RelB regulated pathogen-responsive gene expression programs. This work illustrates the potential utility of systems analyses in guiding the development of combination therapeutics for modulating DC-dependent T cell responses
A theoretical study on the damping of collective excitations in a Bose-Einstein condensate
We study the damping of low-lying collective excitations of condensates in a
weakly interacting Bose gas model within the framework of imaginary time path
integral. A general expression of the damping rate has been obtained in the low
momentum limit for both the very low temperature regime and the higher
temperature regime. For the latter, the result is new and applicable to recent
experiments. Theoretical predictions for the damping rate are compared with the
experimental values.Comment: 15 pages, LaTeX, revised for minor corrections on LaTeX file forma
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