80,439 research outputs found
An efficient error resilience scheme based on wyner-ziv coding for region-of-Interest protection of wavelet based video transmission
In this paper, we propose a bandwidth efficient error resilience scheme for wavelet based video
transmission over wireless channel by introducing an additional Wyner-Ziv (WZ) stream to protect region of
interest (ROI) in a frame. In the proposed architecture, the main video stream is compressed by a generic
wavelet domain coding structure and passed through the error prone channel without any protection.
Meanwhile, the predefined ROI area related wavelet coefficients obtained after an integer wavelet transform
will be specially protected by WZ codec in an additional channel during transmission. At the decoder side, the error-prone ROI related wavelet coefficients will be used as side information to help decoding the WZ stream. Different size of WZ bit streams can be applied in order to meet different bandwidth condition and different
requirement of end users. The simulation results clearly revealed that the proposed scheme has distinct advantages in saving bandwidth comparing with fully applied FEC algorithm to whole video stream and in the meantime offer the robust transmission over error prone channel for certain video applications
Spatial networks with wireless applications
Many networks have nodes located in physical space, with links more common
between closely spaced pairs of nodes. For example, the nodes could be wireless
devices and links communication channels in a wireless mesh network. We
describe recent work involving such networks, considering effects due to the
geometry (convex,non-convex, and fractal), node distribution,
distance-dependent link probability, mobility, directivity and interference.Comment: Review article- an amended version with a new title from the origina
Performance of the sleep-mode mechanism of the new IEEE 802.16m proposal for correlated downlink traffic
There is a considerable interest nowadays in making wireless telecommunication more energy-efficient. The sleep-mode mechanism in WiMAX (IEEE 802.16e) is one of such energy saving measures. Recently, Samsung proposed some modifications on the sleep-mode mechanism, scheduled to appear in the forthcoming IEEE 802.16m standard, aimed at minimizing the signaling overhead. In this work, we present a performance analysis of this proposal and clarify the differences with the standard mechanism included in IEEE 802.16e. We also propose some special algorithms aimed at reducing the computational complexity of the analysis
Electromagnetic modelling and simulation of a high-frequency ground penetrating radar antenna over a concrete cell with steel rods
This work focuses on the electromagnetic modelling and simulation of a highfrequency
Ground-Penetrating Radar (GPR) antenna over a concrete cell with
reinforcing elements. The development of realistic electromagnetic models of GPR
antennas is crucial for accurately predicting GPR responses and for designing
new antennas. We used commercial software implementing the Finite-Integration
technique (CST Microwave Studio) to create a model that is representative of a
1.5 GHz Geophysical Survey Systems, Inc. antenna, by exploiting information
published in the literature (namely, in the PhD Thesis of Dr Craig Warren); our
CST model was validated, in a previous work, by comparisons with FiniteDifference
Time-Domain results and with experimental data, with very good
agreement, showing that the software we used is suitable for the simulation of
antennas in the presence of targets in the near field. In the current paper, we
firstly describe in detail how the CST model of the antenna was implemented;
subsequently, we present new results calculated with the antenna over a
reinforced-concrete cell. Such cell is one of the reference scenarios included in
the Open Database of Radargrams of COST Action TU1208 “Civil engineering
applications of Ground Penetrating Radar” and hosts five circular-section steel
rods, having different diameters, embedded at different depths into the concrete.
Comparisons with a simpler model, where the physical structure of the antenna
is not taken into account, are carried out; the significant differences between the
results of the realistic model and the results of the simplified model confirm the
importance of including accurate models of the actual antennas in GPR
simulations; they also emphasize how salient it is to remove antenna effects as a
pre-processing step of experimental GPR data. The simulation results of the
antenna over the concrete cell presented in this paper are attached to the paper
as ‘Supplementary materials.
Efficient Volumetric Method of Moments for Modeling Plasmonic Thin-Film Solar Cells with Periodic Structures
Metallic nanoparticles (NPs) support localized surface plasmon resonances
(LSPRs), which enable to concentrate sunlight at the active layer of solar
cells. However, full-wave modeling of the plasmonic solar cells faces great
challenges in terms of huge computational workload and bad matrix condition. It
is tremendously difficult to accurately and efficiently simulate near-field
multiple scattering effects from plasmonic NPs embedded into solar cells. In
this work, a preconditioned volume integral equation (VIE) is proposed to model
plasmonic organic solar cells (OSCs). The diagonal block preconditioner is
applied to different material domains of the device structure. As a result,
better convergence and higher computing efficiency are achieved. Moreover, the
calculation is further accelerated by two-dimensional periodic Green's
functions. Using the proposed method, the dependences of optical absorption on
the wavelengths and incident angles are investigated. Angular responses of the
plasmonic OSCs show the super-Lambertian absorption on the plasmon resonance
but near-Lambertian absorption off the plasmon resonance. The volumetric method
of moments and explored physical understanding are of great help to investigate
the optical responses of OSCs.Comment: 11 pages, 6 figure
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