22,867 research outputs found
Resource Allocation for Power Minimization in the Downlink of THP-based Spatial Multiplexing MIMO-OFDMA Systems
In this work, we deal with resource allocation in the downlink of spatial
multiplexing MIMO-OFDMA systems. In particular, we concentrate on the problem
of jointly optimizing the transmit and receive processing matrices, the channel
assignment and the power allocation with the objective of minimizing the total
power consumption while satisfying different quality-of-service requirements. A
layered architecture is used in which users are first partitioned in different
groups on the basis of their channel quality and then channel assignment and
transceiver design are sequentially addressed starting from the group of users
with most adverse channel conditions. The multi-user interference among users
belonging to different groups is removed at the base station using a
Tomlinson-Harashima pre-coder operating at user level. Numerical results are
used to highlight the effectiveness of the proposed solution and to make
comparisons with existing alternatives.Comment: 12 pages, 6 figures, IEEE Trans. Veh. Techno
Adaptive Interference Removal for Un-coordinated Radar/Communication Co-existence
Most existing approaches to co-existing communication/radar systems assume
that the radar and communication systems are coordinated, i.e., they share
information, such as relative position, transmitted waveforms and channel
state. In this paper, we consider an un-coordinated scenario where a
communication receiver is to operate in the presence of a number of radars, of
which only a sub-set may be active, which poses the problem of estimating the
active waveforms and the relevant parameters thereof, so as to cancel them
prior to demodulation. Two algorithms are proposed for such a joint waveform
estimation/data demodulation problem, both exploiting sparsity of a proper
representation of the interference and of the vector containing the errors of
the data block, so as to implement an iterative joint interference removal/data
demodulation process. The former algorithm is based on classical on-grid
compressed sensing (CS), while the latter forces an atomic norm (AN)
constraint: in both cases the radar parameters and the communication
demodulation errors can be estimated by solving a convex problem. We also
propose a way to improve the efficiency of the AN-based algorithm. The
performance of these algorithms are demonstrated through extensive simulations,
taking into account a variety of conditions concerning both the interferers and
the respective channel states
Nonperturbative contributions to a resummed leptonic angular distribution in inclusive neutral vector boson production
We present an analysis of nonperturbative contributions to the transverse
momentum distribution of bosons produced at hadron colliders. The
new data on the angular distribution of Drell-Yan pairs measured
at the Tevatron is shown to be in excellent agreement with a perturbative QCD
prediction based on the Collins-Soper-Sterman (CSS) resummation formalism at
NNLL accuracy. Using these data, we determine the nonperturbative component of
the CSS resummed cross section and estimate its dependence on arbitrary
resummation scales and other factors. With the scale dependence included at the
NNLL level, a significant nonperturbative component is needed to describe the
angular data.Comment: 36 pages, 10 figures, regular article. Revised version accepted for a
publication in Phys.Rev.
Short-time diffusion in concentrated bidisperse hard-sphere suspensions
Diffusion in bidisperse Brownian hard-sphere suspensions is studied by
Stokesian Dynamics (SD) computer simulations and a semi-analytical theoretical
scheme for colloidal short-time dynamics, based on Beenakker and Mazur's method
[Physica 120A, 388 (1983) & 126A, 349 (1984)]. Two species of hard spheres are
suspended in an overdamped viscous solvent that mediates the salient
hydrodynamic interactions among all particles. In a comprehensive parameter
scan that covers various packing fractions and suspension compositions, we
employ numerically accurate SD simulations to compute the initial diffusive
relaxation of density modulations at the Brownian time scale, quantified by the
partial hydrodynamic functions. A revised version of Beenakker and Mazur's
-scheme for monodisperse suspensions is found to exhibit
surprisingly good accuracy, when simple rescaling laws are invoked in its
application to mixtures. The so-modified scheme predicts
hydrodynamic functions in very good agreement with our SD simulation results,
for all densities from the very dilute limit up to packing fractions as high as
.Comment: 12 pages, 6 figure
Fat Chance! Obesity and the Transition from Unemployment to Employment
This paper focuses on estimating the magnitude of any potential weight discrimination by examining whether obese job applicants in Germany get treated or behave differently from non-obese applicants. Based on two waves of rich survey data from the IZA Evaluation dataset, which includes measures that control for education, demographic characteristics, labor market history, psychological factors and health, we estimate differences in job search behavior and labor market outcomes between obese/overweight and healthy weight individuals. Unlike other observational studies which are generally based on obese and non-obese individuals who might already be at different points in the job ladder (e.g., household surveys), in our data, individuals are newly unemployed and all start from the same point. The only subgroup we find in our data experiencing any possible form of labor market discrimination is obese women. Despite making more job applications and engaging more in job training programs, we find some indications that they experienced worse (or at best similar) employment outcomes than healthy weight women. Obese women who found a job also had significantly lower wages than healthy weight women.obesity, discrimination, employment, labor demand
Outage Probability of Dual-Hop Selective AF With Randomly Distributed and Fixed Interferers
The outage probability performance of a dual-hop amplify-and-forward
selective relaying system with global relay selection is analyzed for
Nakagami- fading channels in the presence of multiple interferers at both
the relays and the destination. Two different cases are considered. In the
first case, the interferers are assumed to have random number and locations.
Outage probability using the generalized Gamma approximation (GGA) in the form
of one-dimensional integral is derived. In the second case, the interferers are
assumed to have fixed number and locations. Exact outage probability in the
form of one-dimensional integral is derived. For both cases, closed-form
expressions of lower bounds and asymptotic expressions for high
signal-to-interference-plus-noise ratio are also provided. Simplified
closed-form expressions of outage probability for special cases (e.g., dominant
interferences, i.i.d. interferers, Rayleigh distributed signals) are studied.
Numerical results are presented to show the accuracy of our analysis by
examining the effects of the number and locations of interferers on the outage
performances of both AF systems with random and fixed interferers.Comment: 35 pages, 11 figures, accepted with minor revisions for publication
as a regular paper in the IEEE Transactions on Vehicular Technology on
21/09/201
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