632 research outputs found
A Normalization Model for Analyzing Multi-Tier Millimeter Wave Cellular Networks
Based on the distinguishing features of multi-tier millimeter wave (mmWave)
networks such as different transmit powers, different directivity gains from
directional beamforming alignment and path loss laws for line-of-sight (LOS)
and non-line-of-sight (NLOS) links, we introduce a normalization model to
simplify the analysis of multi-tier mmWave cellular networks. The highlight of
the model is that we convert a multi-tier mmWave cellular network into a
single-tier mmWave network, where all the base stations (BSs) have the same
normalized transmit power 1 and the densities of BSs scaled by LOS or NLOS
scaling factors respectively follow piecewise constant function which has
multiple demarcation points. On this basis, expressions for computing the
coverage probability are obtained in general case with beamforming alignment
errors and the special case with perfect beamforming alignment in the
communication. According to corresponding numerical exploration, we conclude
that the normalization model for multi-tier mmWave cellular networks fully
meets requirements of network performance analysis, and it is simpler and
clearer than the untransformed model. Besides, an unexpected but sensible
finding is that there is an optimal beam width that maximizes coverage
probability in the case with beamforming alignment errors.Comment: 7 pages, 4 figure
End to End Performance Analysis of Relay Cooperative Communication Based on Parked Cars
Parking lots (PLs) are usually full with cars. If these cars are formed into
a self-organizing vehicular network, they can be new kind of road side units
(RSUs) in urban area to provide communication data forwarding between mobile
terminals nearby and a base station. However cars in PLs can leave at any time,
which is neglected in the existing studies. In this paper, we investigate relay
cooperative communication based on parked cars in PLs. Taking the impact of the
car's leaving behavior into consideration, we derive the expressions of outage
probability in a two-hop cooperative communication and its link capacity.
Finally, the numerical results show that the impact of a car's arriving time is
greater than the impact of the duration the car has parked on outage
probability.Comment: 7 pages, 7 figures, accepted by ICACT201
SEAL: Simultaneous Label Hierarchy Exploration And Learning
Label hierarchy is an important source of external knowledge that can enhance
classification performance. However, most existing methods rely on predefined
label hierarchies that may not match the data distribution. To address this
issue, we propose Simultaneous label hierarchy Exploration And Learning (SEAL),
a new framework that explores the label hierarchy by augmenting the observed
labels with latent labels that follow a prior hierarchical structure. Our
approach uses a 1-Wasserstein metric over the tree metric space as an objective
function, which enables us to simultaneously learn a data-driven label
hierarchy and perform (semi-)supervised learning. We evaluate our method on
several datasets and show that it achieves superior results in both supervised
and semi-supervised scenarios and reveals insightful label structures. Our
implementation is available at https://github.com/tzq1999/SEAL
Vehicle Detection Using Android Smartphones
Rear-end collisions are the most common traffic accidents. Technologies, such as collision warning systems, are developed to reduce the risks of rear-end collisions. This study presents a mobile technology using smartphones to detect the leading vehicle, allowing the possibility to make collision warning systems more affordable and portable. This technology uses the rear camera of an Android smartphone to capture images of driving scenes, and then uses advanced computer vision algorithms to detect and track the leading vehicle. This study may have important applications to improve driving safety
A constructive characterization of total domination vertex critical graphs
AbstractLet G be a graph of order n and maximum degree Δ(G) and let γt(G) denote the minimum cardinality of a total dominating set of a graph G. A graph G with no isolated vertex is the total domination vertex critical if for any vertex v of G that is not adjacent to a vertex of degree one, the total domination number of G−v is less than the total domination number of G. We call these graphs γt-critical. For any γt-critical graph G, it can be shown that n≤Δ(G)(γt(G)−1)+1. In this paper, we prove that: Let G be a connected γt-critical graph of order n (n≥3), then n=Δ(G)(γt(G)−1)+1 if and only if G is regular and, for each v∈V(G), there is an A⊆V(G)−{v} such that N(v)∩A=0̸, the subgraph induced by A is 1-regular, and every vertex in V(G)−A−{v} has exactly one neighbor in A
Towards milli-Hertz laser frequency noise on a chip
Narrow-linewidth lasers are important to many applications spanning precision metrology to sensing systems. Their miniaturization in the form of on-chip lasers is receiving increasing attention. Here, a noise level that is consistent with a fundamental frequency noise of 9 mHzâ‹…Hz/Hz linewidth (60 mHz linewidth) is measured in a Brillouin laser. The results leverage ultra-high-Q silica-on-silicon resonators and point towards a new performance target for chip-based laser platforms
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