303 research outputs found
Vision Aided Environment Semantics Extraction and Its Application in mmWave Beam Selection
In this letter, we propose a novel mmWave beam selection method based on the
environment semantics that are extracted from camera images taken at the user
side. Specifically, we first define the environment semantics as the spatial
distribution of the scatterers that affect the wireless propagation channels
and utilize the keypoint detection technique to extract them from the input
images. Then, we design a deep neural network with environment semantics as the
input that can output the optimal beam pairs at UE and BS. Compared with the
existing beam selection approaches that directly use images as the input, the
proposed semantic-based method can explicitly obtain the environmental features
that account for the propagation of wireless signals, and thus reduce the
burden of storage and computation. Simulation results show that the proposed
method can precisely estimate the location of the scatterers and outperform the
existing image or LIDAR based works
Multi-User Matching and Resource Allocation in Vision Aided Communications
Visual perception is an effective way to obtain the spatial characteristics
of wireless channels and to reduce the overhead for communications system. A
critical problem for the visual assistance is that the communications system
needs to match the radio signal with the visual information of the
corresponding user, i.e., to identify the visual user that corresponds to the
target radio signal from all the environmental objects. In this paper, we
propose a user matching method for environment with a variable number of
objects. Specifically, we apply 3D detection to extract all the environmental
objects from the images taken by multiple cameras. Then, we design a deep
neural network (DNN) to estimate the location distribution of users by the
images and beam pairs at multiple moments, and thereby identify the users from
all the extracted environmental objects. Moreover, we present a resource
allocation method based on the taken images to reduce the time and spectrum
overhead compared to traditional resource allocation methods. Simulation
results show that the proposed user matching method outperforms the existing
methods, and the proposed resource allocation method can achieve
transmission rate of the traditional resource allocation method but with the
time and spectrum overhead significantly reduced.Comment: 34 pages, 21 figure
Multi-Camera View Based Proactive BS Selection and Beam Switching for V2X
Due to the short wavelength and large attenuation of millimeter-wave
(mmWave), mmWave BSs are densely distributed and require beamforming with high
directivity. When the user moves out of the coverage of the current BS or is
severely blocked, the mmWave BS must be switched to ensure the communication
quality. In this paper, we proposed a multi-camera view based proactive BS
selection and beam switching that can predict the optimal BS of the user in the
future frame and switch the corresponding beam pair. Specifically, we extract
the features of multi-camera view images and a small part of channel state
information (CSI) in historical frames, and dynamically adjust the weight of
each modality feature. Then we design a multi-task learning module to guide the
network to better understand the main task, thereby enhancing the accuracy and
the robustness of BS selection and beam switching. Using the outputs of all
tasks, a prior knowledge based fine tuning network is designed to further
increase the BS switching accuracy. After the optimal BS is obtained, a beam
pair switching network is proposed to directly predict the optimal beam pair of
the corresponding BS. Simulation results in an outdoor intersection environment
show the superior performance of our proposed solution under several metrics
such as predicting accuracy, achievable rate, harmonic mean of precision and
recall
Enhanced thermoelectric transport properties of La0.98Sr0.02CoO3-BiCuSeO composite
We report a facile method to enhance the thermoelectric efficiency of La0.98Sr0.02CoO3 by introducing BiCuSeO as a secondary phase with ultra-low thermal conductivity. Inclusion of secondary phase results in reducing the total thermal conductivity by suppressing the lattice and electronic thermal conductivities and also contributes to enhancement in the Seebeck coefficient. The wide grain size distribution of La0.98Sr0.02CoO3-BiCuSeO composite facilitates in breaking the interlinked transport properties through increased scattering of different wavelength phonons. The combined effect of enhanced Seebeck coefficient and ultra-low thermal conductivity, results in an improved ZT value of 0.07 at 923 K. The proposed strategy can be opted for improvement in the thermoelectric efficiency of other thermoelectric materials as well
6G Network AI Architecture for Everyone-Centric Customized Services
Mobile communication standards were developed for enhancing transmission and
network performance by using more radio resources and improving spectrum and
energy efficiency. How to effectively address diverse user requirements and
guarantee everyone's Quality of Experience (QoE) remains an open problem. The
Sixth Generation (6G) mobile systems will solve this problem by utilizing
heterogenous network resources and pervasive intelligence to support
everyone-centric customized services anywhere and anytime. In this article, we
first coin the concept of Service Requirement Zone (SRZ) on the user side to
characterize and visualize the integrated service requirements and preferences
of specific tasks of individual users. On the system side, we further introduce
the concept of User Satisfaction Ratio (USR) to evaluate the system's overall
service ability of satisfying a variety of tasks with different SRZs. Then, we
propose a network Artificial Intelligence (AI) architecture with integrated
network resources and pervasive AI capabilities for supporting customized
services with guaranteed QoEs. Finally, extensive simulations show that the
proposed network AI architecture can consistently offer a higher USR
performance than the cloud AI and edge AI architectures with respect to
different task scheduling algorithms, random service requirements, and dynamic
network conditions
Roadmap on Perovskite Light-Emitting Diodes
In recent years, the field of metal-halide perovskite emitters has rapidly
emerged as a new community in solid-state lighting. Their exceptional
optoelectronic properties have contributed to the rapid rise in external
quantum efficiencies (EQEs) in perovskite light-emitting diodes (PeLEDs) from
<1% (in 2014) to approaching 30% (in 2023) across a wide range of wavelengths.
However, several challenges still hinder their commercialization, including the
relatively low EQEs of blue/white devices, limited EQEs in large-area devices,
poor device stability, as well as the toxicity of the easily accessible lead
components and the solvents used in the synthesis and processing of PeLEDs.
This roadmap addresses the current and future challenges in PeLEDs across
fundamental and applied research areas, by sharing the community's
perspectives. This work will provide the field with practical guidelines to
advance PeLED development and facilitate more rapid commercialization.Comment: 103 pages, 29 figures. This is the version of the article before peer
review or editing, as submitted by an author to Journal of Physics:
Photonics. IOP Publishing Ltd is not responsible for any errors or omissions
in this version of the manuscript or any version derived from i
Search for the decay
We search for radiative decays into a weakly interacting neutral
particle, namely an invisible particle, using the produced through the
process in a data sample of
decays collected by the BESIII detector
at BEPCII. No significant signal is observed. Using a modified frequentist
method, upper limits on the branching fractions are set under different
assumptions of invisible particle masses up to 1.2 . The upper limit corresponding to an invisible particle with zero mass
is 7.0 at the 90\% confidence level
Measurements of the absolute branching fractions of decays
Based on 2.93~fb collision data taken at center-of-mass
energy of 3.773 GeV by the BESIII detector, we report the measurements of the
absolute branching fractions of , , , , , ,
, , and . The decays , , , , and are observed for the
first time. The branching fractions of the decays , , ,
and are measured with improved precision compared
to the world-average values.Comment: 11 pages, 5 figure
Measurement of the branching fraction of and search for a CP-violating asymmetry in η′→π+π−e+e− at BESIII
The rare decay η′→π+π-e+e- is studied using a sample of 1.3×109 J/ψ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be (2.42±0.05stat±0.08syst)×10-3. Due to the inclusion of new data, this result supersedes the last BESIII result on this branching fraction. In addition, the CP-violating asymmetry in the angle between the decay planes of the π+π - pair and the e+e - pair is investigated. A measurable value would indicate physics beyond the standard model; the result is ACP=(2.9±3.7stat±1.1syst)%, which is consistent with the standard model expectation of no CP-violation. The precision is comparable to the asymmetry measurement in the KL0→π+π-e+e- decay where the observed (14±2)% effect is driven by a standard model mechanism
- …