40,282 research outputs found
Multiple-Level Power Allocation Strategy for Secondary Users in Cognitive Radio Networks
In this paper, we propose a multiple-level power allocation strategy for the
secondary user (SU) in cognitive radio (CR) networks. Different from the
conventional strategies, where SU either stays silent or transmit with a
constant/binary power depending on the busy/idle status of the primary user
(PU), the proposed strategy allows SU to choose different power levels
according to a carefully designed function of the receiving energy. The way of
the power level selection is optimized to maximize the achievable rate of SU
under the constraints of average transmit power at SU and average interference
power at PU. Simulation results demonstrate that the proposed strategy can
significantly improve the performance of SU compared to the conventional
strategies.Comment: 12 page
Two-Sample Tests for High Dimensional Means with Thresholding and Data Transformation
We consider testing for two-sample means of high dimensional populations by
thresholding. Two tests are investigated, which are designed for better power
performance when the two population mean vectors differ only in sparsely
populated coordinates. The first test is constructed by carrying out
thresholding to remove the non-signal bearing dimensions. The second test
combines data transformation via the precision matrix with the thresholding.
The benefits of the thresholding and the data transformations are showed by a
reduced variance of the test thresholding statistics, the improved power and a
wider detection region of the tests. Simulation experiments and an empirical
study are performed to confirm the theoretical findings and to demonstrate the
practical implementations.Comment: 64 page
Rotationally symmetric harmonic diffeomorphisms between surfaces
In this paper, we show that the nonexistence of rotationally symmetric
harmonic diffeomorphism between the unit disk without the origin and a
punctured disc with hyperbolic metric on the target.Comment: Minor typos correcte
Coupled effects of local movement and global interaction on contagion
By incorporating segregated spatial domain and individual-based linkage into
the SIS (susceptible-infected-susceptible) model, we investigate the coupled
effects of random walk and intragroup interaction on contagion. Compared with
the situation where only local movement or individual-based linkage exists, the
coexistence of them leads to a wider spread of infectious disease. The roles of
narrowing segregated spatial domain and reducing mobility in epidemic control
are checked, these two measures are found to be conducive to curbing the spread
of infectious disease. Considering heterogeneous time scales between local
movement and global interaction, a log-log relation between the change in the
number of infected individuals and the timescale is found. A theoretical
analysis indicates that the evolutionary dynamics in the present model is
related to the encounter probability and the encounter time. A functional
relation between the epidemic threshold and the ratio of shortcuts, and a
functional relation between the encounter time and the timescale are
found
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