9,923 research outputs found
Optimal Power Allocation for Artificial Noise under Imperfect CSI against Spatially Random Eavesdroppers
In this correspondence, we study the secure multiantenna transmission with
artificial noise (AN) under imperfect channel state information in the presence
of spatially randomly distributed eavesdroppers. We derive the optimal
solutions of the power allocation between the information signal and the AN for
minimizing the secrecy outage probability (SOP) under a target secrecy rate and
for maximizing the secrecy rate under a SOP constraint, respectively. Moreover,
we provide an interesting insight that channel estimation error affects the
optimal power allocation strategy in opposite ways for the above two
objectives. When the estimation error increases, more power should be allocated
to the information signal if we aim to decrease the rate-constrained SOP,
whereas more power should be allocated to the AN if we aim to increase the
SOP-constrained secrecy rate.Comment: 7 pages, 6 figure
Improving Anti-Eavesdropping Ability without Eavesdropper's CSI: A Practical Secure Transmission Design Perspective
This letter studies the practical design of secure transmissions without
knowing eavesdropper's channel state information (ECSI). An ECSI-irrelevant
metric is introduced to quantize the intrinsic anti-eavesdropping ability (AEA)
that the transmitter has on confronting the eavesdropper via secrecy encoding
together with artificial-noise-aided signaling. Non-adaptive and adaptive
transmission schemes are proposed to maximize the AEA with the optimal encoding
rates and power allocation presented in closed-form expressions. Analyses and
numerical results show that maximizing the AEA is equivalent to minimizing the
secrecy outage probability (SOP) for the worst case by ignoring eavesdropper's
receiver noise. Therefore, the AEA is a useful alternative to the SOP for
assessing and designing secure transmissions when the ECSI cannot be prior
known.Comment: 4 pages, 2 figures, to be published on IEEE Wireless Communications
Letters (WCL
Delivery-Secrecy Tradeoff for Cache-Enabled Stochastic Networks: Content Placement Optimization
Wireless caching has been widely recognized as a promising technique for
efficient content delivery. In this paper, by taking different file secrecy
levels into consideration, physical-layer security oriented content placement
is optimized in a stochastic cache-enabled cellular network. We propose an
analytical framework to investigate the nontrivial file delivery-secrecy
tradeoff. Specifically, we first derive the closed-form expressions for the
file hit and secrecy probabilities. The global optimal probabilistic content
placement policy is then analytically derived in terms of hit probability
maximization under file secrecy constraints. Numerical results are demonstrated
to verify our analytical findings and show that the targeted file secrecy
levels are crucial in balancing the file delivery-secrecy tradeoff.Comment: 5 pages, 4 figures, accepted to be published in IEEE Transactions on
Vehicular Technolog
estimates for fractional schrodinger operators with kato class potentials
Let , , belongs to the higher
order Kato class K_{2\alpha}(\mathbbm{R}^n). For , we
prove a polynomial upper bound of in
terms of time . Both the smoothing exponent and the growth order in
are almost optimal compared to the free case. The main ingredients in our
proof are pointwise heat kernel estimates for the semigroup . We
obtain a Gaussian upper bound with sharp coefficient for integral and
a polynomial decay for fractal .Comment: 37 pages. Final version, to appear in J. Differential Equation
Secure and Energy-Efficient Transmissions in Cache-Enabled Heterogeneous Cellular Networks: Performance Analysis and Optimization
This paper studies physical-layer security for a cache-enabled heterogeneous
cellular network comprised of a macro base station and multiple small base
stations (SBSs). We investigate a joint design on caching placement and file
delivery for realizing secure and energy-efficient transmissions against
randomly distributed eavesdroppers. We propose a novel hybrid "most popular
content" and "largest content diversity" caching placement policy to distribute
files of different popularities. Depending on the availability and placement of
the requested file, we employ three cooperative transmission schemes, namely,
distributed beamforming, frequency-domain orthogonal transmission, and best SBS
relaying, respectively. We derive analytical expressions for the connection
outage probability and secrecy outage probability for each transmission scheme.
Afterwards, we design the optimal transmission rates and caching allocation
successively to achieve a maximal overall secrecy throughput and secrecy energy
efficiency, respectively. Numerical results verify the theoretical analyses and
demonstrate the superiority of the proposed hybrid caching policy.Comment: 13 pages in double-column, 9 figures, accepted for publication on
IEEE Transactions on Communication
Cooper instability generated by attractive fermion-fermion interaction in the two-dimensional semi-Dirac semimetals
Cooper instability associated with superconductivity in the two-dimensional
semi-Dirac semimetals is attentively studied in the presence of attractive
Cooper-pairing interaction, which is the projection of an attractive
fermion-fermion interaction. Performing the standard renormalization group
analysis shows that the Cooper theorem is violated at zero chemical potential
but instead Cooper instability can be generated only if the absolute strength
of fermion-fermion coupling exceeds certain critical value and transfer
momentum is restricted to a confined region, which is determined by the initial
conditions. Rather, the Cooper theorem would be instantly restored once a
finite chemical potential is introduced and thus a chemical potential-tuned
phase transition is expected. Additionally, we briefly examine the effects of
impurity scatterings on the Cooper instability at zero chemical potential,
which in principle are harmful to Cooper instability although they can enhance
the density of states of systems. Furthermore, the influence of competition
between a finite chemical potential and impurities upon the Cooper instability
is also simply investigated. These results are expected to provide instructive
clues for exploring unconventional superconductors in the kinds of semimetals.Comment: 18 pages; 14 figure
On the Relations of Correlation Filter Based Trackers and Struck
In recent years, two types of trackers, namely correlation filter based
tracker (CF tracker) and structured output tracker (Struck), have exhibited the
state-of-the-art performance. However, there seems to be lack of analytic work
on their relations in the computer vision community. In this paper, we
investigate two state-of-the-art CF trackers, i.e., spatial regularization
discriminative correlation filter (SRDCF) and correlation filter with limited
boundaries (CFLB), and Struck, and reveal their relations. Specifically, after
extending the CFLB to its multiple channel version we prove the relation
between SRDCF and CFLB on the condition that the spatial regularization factor
of SRDCF is replaced by the masking matrix of CFLB. We also prove the
asymptotical approximate relation between SRDCF and Struck on the conditions
that the spatial regularization factor of SRDCF is replaced by an indicator
function of object bounding box, the weights of SRDCF in its loss item are
replaced by those of Struck, the linear kernel is employed by Struck, and the
search region tends to infinity. Extensive experiments on public benchmarks
OTB50 and OTB100 are conducted to verify our theoretical results. Moreover, we
explain how detailed differences among SRDCF, CFLB, and Struck would give rise
to slightly different performances on visual sequence
Salient Object Detection: A Discriminative Regional Feature Integration Approach
Salient object detection has been attracting a lot of interest, and recently
various heuristic computational models have been designed. In this paper, we
formulate saliency map computation as a regression problem. Our method, which
is based on multi-level image segmentation, utilizes the supervised learning
approach to map the regional feature vector to a saliency score. Saliency
scores across multiple levels are finally fused to produce the saliency map.
The contributions lie in two-fold. One is that we propose a discriminate
regional feature integration approach for salient object detection. Compared
with existing heuristic models, our proposed method is able to automatically
integrate high-dimensional regional saliency features and choose discriminative
ones. The other is that by investigating standard generic region properties as
well as two widely studied concepts for salient object detection, i.e.,
regional contrast and backgroundness, our approach significantly outperforms
state-of-the-art methods on six benchmark datasets. Meanwhile, we demonstrate
that our method runs as fast as most existing algorithms
Adaptive Full-Duplex Jamming Receiver for Secure D2D Links in Random Networks
Device-to-device (D2D) communication raises new transmission secrecy
protection challenges, since conventional physical layer security approaches,
such as multiple antennas and cooperation techniques, are invalid due to its
resource/size constraints. The full-duplex (FD) jamming receiver, which
radiates jamming signals to confuse eavesdroppers when receiving the desired
signal simultaneously, is a promising candidate. Unlike existing endeavors that
assume the FD jamming receiver always improves the secrecy performance compared
with the half-duplex (HD) receiver, we show that this assumption highly depends
on the instantaneous residual self-interference cancellation level and may be
invalid. We propose an adaptive jamming receiver operating in a switched FD/HD
mode for a D2D link in random networks. Subject to the secrecy outage
probability constraint, we optimize the transceiver parameters, such as
signal/jamming powers, secrecy rates and mode switch criteria, to maximize the
secrecy throughput. Most of the optimization operations are taken off-line and
only very limited on-line calculations are required to make the scheme with low
complexity. Furthermore, some interesting insights are provided, such as the
secrecy throughput is a quasi-concave function. Numerical results are
demonstrated to verify our theoretical findings, and to show its superiority
compared with the receiver operating in the FD or HD mode only
On small set of one-way LOCC indistinguishability of maximally entangled states
In this paper, we study the one-way local operations and classical
communication (LOCC) problem. In with
, we construct a set of one-way LOCC
indistinguishable maximally entangled states which are generalized Bell states.
Moreover, we show that there are four maximally entangled states which cannot
be perfectly distinguished by one-way LOCC measurements for any dimension
.Comment: 10 pages.Very recently, we became aware of related work \cite{Zhang2}
in which the same states in
is proved to be one-way LOCC
indistinguishable. arXiv admin note: text overlap with arXiv:1310.4220 by
other autho
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