8,013 research outputs found
Cross-layer optimisation for topology design of wireless multicast networks via network coding
One of the main challenges towards reliable multicast transmissions over wireless networks is the dynamics of the wireless links (e.g. wireless errors, fading, interference, collisions, etc.) that can cause retransmissions overhead over the limited available bandwidth. To this end this paper considers the scenario of wireless multicast networks where network coding is applied to improve network throughput. We first propose a novel cross-layer optimisation framework for network topology design in order to optimise the wireless multicast rate, data flow of the wireless links, energy supply and node lifetime. The performance of the proposed solution is evaluated and compared against other solutions from the literature in terms of system throughput, total energy, and network lifetime. The results show that the proposed cross-layer design outperforms the other schemes involved, reaching up to 50% increase in the system throughput
Cross-layer topology design for network coding based wireless multicasting
This paper considers wireless multicast networks where network coding (NC) is applied to improve network throughput. A novel joint topology and cross-layer design is proposed to miximize the network throughput subject to various quality-of-service constraints, such as: wireless multicast rate, wireless link capacity, energy supply and network lifetime. Specifically, a heuristic NC-based link-controlled routing tree algorithm is developed to reduce the number of required intermediate nodes. The proposed algorithm facilitates the optimization of the wireless multicast rate, data flow of wireless links, energy supply and lifetime of nodes through a novel cross-layer design. The proposed joint topology and cross-layer design is evaluated and compared against other schemes from the literature. The results show that the proposed scheme can achieve up to 50% increase in the system throughput when compared to a classic approach
On the energy-delay tradeoff and relay positioning of wireless butterfly networks
This paper considers energy-delay tradeoff (EDT) of data transmission in wireless network coded butterfly networks (WNCBNs) where two sources convey their data to two destinations with the assistance of a relay employing either physical-layer network coding (PNC) or analog network coding (ANC). Hybrid automatic repeat request with incremental redundancy (HARQIR) is applied for a reliable communication. Particularly, we first investigate the EDT of both PNC and ANC schemes in WNCBNs to evaluate their energy efficiency. It is found that there is no advantage of using a relay in a high power regime. However, in a low power regime, the PNC scheme is shown to be more energy efficient than both the ANC and direct transmission (DT) schemes if the relay is located far from the sources, while both the PNC and ANC schemes are less energy efficient than the DT scheme when the relay is located near the sources. Additionally, algorithms that optimise relay positioning are developed based on two criteria - minimising total transmission delays and minimising total energy consumption subject to node location and power allocation constraints. This optimisation can be considered as a benchmark for relay positioning in either a low-latency or a low-energy-consumption WNCBN
Geometric entanglement from matrix product state representations
An efficient scheme to compute the geometric entanglement per lattice site
for quantum many-body systems on a periodic finite-size chain is proposed in
the context of a tensor network algorithm based on the matrix product state
representations. It is systematically tested for three prototypical critical
quantum spin chains, which belong to the same Ising universality class. The
simulation results lend strong support to the previous claim [Q.-Q. Shi, R.
Or\'{u}s, J. O. Fj{\ae}restad, and H.-Q. Zhou, New J. Phys \textbf{12}, 025008
(2010); J.-M. St\'{e}phan, G. Misguich, and F. Alet, Phys. Rev. B \textbf{82},
180406R (2010)] that the leading finite-size correction to the geometric
entanglement per lattice site is universal, with its remarkable connection to
the celebrated Affleck-Ludwig boundary entropy corresponding to a conformally
invariant boundary condition.Comment: 4+ pages, 3 figure
Observation of indirect ionization of W7+ in an electron-beam ion-trap plasma
In this work, visible and extreme ultraviolet spectra of W7+ are measured
using the high-temperature superconducting electron-beam ion trap (EBIT) at the
Shanghai EBIT Laboratory under extremely low-energy conditions (lower than the
nominal electron-beam energy of 130 eV). The relevant atomic structure is
calculated using the flexible atomic code package based on the relativistic
configuration interaction method. The GRASP2K code, in the framework of the
multiconfiguration Dirac-Hartree-Fock method, is employed as well for
calculating the wavelength of the M1 transition in the ground configuration of
W7+. A line from the W7+ ions is observed at a little higher electron-beam
energy than the ionization potential for W4+, making this line appear to be
from W5+. A hypothesis for the charge-state evolution of W7+ is proposed based
on our experimental and theoretical results; that is, the occurrence of W7+
ions results from indirect ionization caused by stepwise excitation between
some metastable states of lower-charge-state W ions, at the nominal
electron-beam energy of 59 eV
From the Complete Yang Model to Snyder's Model, de Sitter Special Relativity and Their Duality
By means of Dirac procedure, we re-examine Yang's quantized space-time model,
its relation to Snyder's model, the de Sitter special relativity and their
UV-IR duality. Starting from a dimensionless dS_5-space in a 5+1-d Mink-space a
complete Yang model at both classical and quantum level can be presented and
there really exist Snyder's model, the dS special relativity and the duality.Comment: 7 papge
Antiviral treatment alters the frequency of activating and inhibitory receptor-expressing natural killer cells in chronic Hepatitis B virus infected patients
Natural killer (NK) cells play a critical role in innate antiviral immunity, but little is known about the impact of antiviral therapy on the frequency of NK cell subsets. To this aim, we performed this longitudinal study to examine the dynamic changes of the frequency of different subsets of NK cells in CHB patients after initiation of tenofovir or adefovir therapy. We found that NK cell numbers and subset distribution differ between CHB patients and normal subjects; furthermore, the association was found between ALT level and CD158b+ NK cell in HBV patients. In tenofovir group, the frequency of NK cells increased during the treatment accompanied by downregulated expression of NKG2A and KIR2DL3. In adefovir group, NK cell numbers did not differ during the treatment, but also accompanied by downregulated expression of NKG2A and KIR2DL3. Our results demonstrate that treatment with tenofovir leads to viral load reduction, and correlated with NK cell frequencies in peripheral blood of chronic hepatitis B virus infection. In addition, treatments with both tenofovir and adefovir in chronic HBV infected patients induce a decrease of the frequency of inhibitory receptor+ NK cells, which may account for the partial restoration of the function of NK cells in peripheral blood following treatment
- …