8,046 research outputs found
Optimal Resource Allocation for Wireless Powered Mobile Edge Computing with Dynamic Task Arrivals
This paper considers a wireless powered multiuser mobile edge computing (MEC)
system, where a multi-antenna access point (AP) employs the radio-frequency
(RF) signal based wireless power transfer (WPT) to charge a number of
distributed users, and each user utilizes the harvested energy to execute
computation tasks via local computing and task offloading. We consider the
frequency division multiple access (FDMA) protocol to support simultaneous task
offloading from multiple users to the AP. Different from previous works that
considered one-shot optimization with static task models, we study the joint
computation and wireless resource allocation optimization with dynamic task
arrivals over a finite time horizon consisting of multiple slots. Under this
setup, our objective is to minimize the system energy consumption including the
AP's transmission energy and the MEC server's computing energy over the whole
horizon, by jointly optimizing the transmit energy beamforming at the AP, and
the local computing and task offloading strategies at the users over different
time slots. To characterize the fundamental performance limit of such systems,
we focus on the offline optimization by assuming the task and channel
information are known a-priori at the AP. In this case, the energy minimization
problem corresponds to a convex optimization problem. Leveraging the Lagrange
duality method, we obtain the optimal solution to this problem in a well
structure. It is shown that in order to maximize the system energy efficiency,
the optimal number of task input-bits at each user and the AP are monotonically
increasing over time, and the offloading strategies at different users depend
on both the wireless channel conditions and the task load at the AP. Numerical
results demonstrate the benefit of the proposed joint-WPT-MEC design over
alternative benchmark schemes without such joint design.Comment: 7 pages, 3 figures, and Accepted by IEEE ICC 2019, Shanghai, Chin
Emergence of cooperation induced by preferential learning
The evolutionary Prisoner's Dilemma Game (PDG) and the Snowdrift Game (SG)
with preferential learning mechanism are studied in the Barab\'asi-Albert
network. Simulation results demonstrate that the preferential learning of
individuals remarkably promotes the cooperative behavior for both two games
over a wide range of payoffs. To understand the effect of preferential learning
on the evolution of the systems, we investigate the time series of the
cooperator density for different preferential strength and payoffs. It is found
that in some specific cases two games both show the -scaling behaviors,
which indicate the existence of long range correlation. We also figure out that
when the large degree nodes have high probability to be selected, the PDG
displays a punctuated equilibrium-type behavior. On the contrary, the SG
exhibits a sudden increase feature. These temporary instable behaviors are
ascribed to the strategy shift of the large degree nodes.Comment: 10 pages, 5 figure
Disentangling boson peaks and Van Hove singularities in a model glass
Using the example of a two-dimensional macroscopic model glass in which the
interparticle forces can be precisely measured, we obtain strong hints for
resolving a controversy concerning the origin of the anomalous enhancement of
the vibrational spectrum in glasses (boson peak). Whereas many authors
attribute this anomaly to the structural disorder, some other authors claim
that the short-range order, leading to washed-out Van Hove singularities, would
cause the boson-peak anomaly. As in our model system, the disorder-induced and
shortrange--order-induced features can be completely separated, we are able to
discuss the controversy about the boson peak in real glasses in a new light.
Our findings suggest that the interpretation of the boson peak in terms of
short-range order only, might result from a coincidence of the two phenomena in
the materials studied. In general, as we show, the two phenomena both exist,
but are two completely separate entities.Comment: 7 pages, 9 figure
Dynamical Coarse Graining of Large Scale-Free Boolean networks
We present a renormalization-grouplike method performed in the state space
for detecting the dynamical behaviors of large scale-free Boolean networks,
especially for the chaotic regime as well as the edge of chaos. Numerical
simulations with different coarse-graining level show that the state space
networks of scale-free Boolean networks follow universal power-law
distributions of in and out strength, in and out degree, as well as weight.
These interesting results indicate scale-free Boolean networks still possess
self-organized mechanism near the edge of chaos in the chaotic regime. The
number of state nodes as a function of biased parameter for distinct
coarse-graining level also demonstrates that the power-law behaviors are not
the artifact of coarse-graining procedure. Our work may also shed some light on
the investigation of brain dynamics.Comment: 5 pages, 6 figure
Diffusion-limited-aggregation on a directed small world network
For real world systems, nonuniform medium is ubiquitous. Therefore, we
investigate the diffusion-limited-aggregation process on a two dimensional
directed small-world network instead of regular lattice. The network structure
is established by rewiring connections on the two dimensional directed lattice.
Those rewired edges are controlled by two parameters and , which
characterize the spatial length and the density of the long-range connections,
respectively. Simulations show that there exists a maximum value of the fractal
dimension when equals zero. Interestingly, we find that the symmetry
of the aggregation pattern is broken when rewired connections are long enough,
which may be an explanation for the formation of asymmetrical fractal in
nature. Then, we perform multifractal analysis on the patterns further.Comment: 5 pages, 5 figure
Morita Equivalence and Interpolation of The Dirac-Born-infeld Theory on the Non-Commutative Torus
In the noncommutative Dirac-Born-Infeld action with Chern-Simons term, an
interpolation field is used in both DBI action and Chern-Simons term.
The Morita equivalence is discussed in both the lagrangian and the Hamiltonian
formalisms, which is more transparent in this treatment.Comment: 6 pages, latex, no figure
A microscopic description for polarization in particle scatterings
We propose a microscopic description for the polarization from the first
principle through the spin-orbit coupling in particle collisions. The model is
different from previous ones based on local equilibrium assumptions for the
spin degree of freedom. It is based on scatterings of particles as wave
packets, an effective method to deal with particle scatterings at specified
impact parameters. The polarization is then the consequence of particle
collisions in a non-equilibrium state of spins. The spin-vorticity coupling
naturally emerges from the spin-orbit one encoded in polarized scattering
amplitudes of collisional integrals when one assumes local equilibrium in
momentum but not in spin.Comment: RevTex 4, 54 pages, 4 figure
Epidemic spread in weighted scale-free networks
In this letter, we investigate the detailed epidemic spreading process in
scale-free networks with links' weights that denote familiarity between two
individuals and find that spreading velocity reaches a peak quickly then decays
in a power-law form. Numerical study exhibits that the nodes with larger
strength is preferential to be infected, but the hierarchical dynamics are not
clearly found, which is different from the well-known result in unweighed
network case. In addition, also by numerical study, we demonstrate that larger
dispersion of weight of networks results in slower spreading, which indicates
that epidemic spreads more quickly on unweighted scale-free networks than on
weighted scale-free networks with the same condition.Comment: 4 pages, 5 figures. Chin. Phys. Lett in Press 200
Implementation and verification of different ECC mitigation designs for BRAMs in flash-based FPGAs
Embedded RAM blocks (BRAMs) in field programmable gate arrays (FPGAs) are
susceptible to single event effects (SEEs) induced by environmental factors
such as cosmic rays, heavy ions, alpha particles and so on. As technology
scales, the issue will be more serious. In order to tackle this issue, two
different error correcting codes (ECCs), the shortened Hamming codes and
shortened BCH codes, are investigated in this paper. The concrete design
methods of the codes are presented. Also, the codes are both implemented in
flash-based FPGAs. Finally, the synthesis report and simulation results are
presented in the paper. Moreover, the heavy-ion experiments are performed, the
experimental results indicate that the error cross-section using the shortened
Hamming codes can be reduced by two orders of magnitude compared with the
device without mitigation, and no errors are discovered in the experiments for
the device using the shortened BCH codes
Epidemic spreading and immunization with identical infectivity
In this paper, a susceptible-infected-susceptible (SIS) model with identical
infectivity, where each node is assigned with the same capability of active
contacts, , at each time step, is presented. We found that on scale-free
networks, the density of the infected nodes shows the existence of threshold,
whose value equals 1/A, both demonstrated by analysis and numerical simulation.
The infected population grows in an exponential form and follows hierarchical
dynamics, indicating that once the highly connected hubs are reached, the
infection pervades almost the whole network in a progressive cascade. In
addition, the effects of random, proportional, and targeted immunization for
this model are investigated. Based on the current model and for heterogenous
networks, the targeted strategy performs best, while the random strategy is
much more efficient than in the standard SIS model. The present results could
be of practical importance in the setup of dynamic control strategies.Comment: 6 pages, 7 figure
- …