1,873,369 research outputs found
Physical layer DVB-SH performance prediction based on mutual information
Full text linkDigital Video Broadcasting-Satellite Handled (DVB-SH) is a hybrid satellite terrestrial broadcasting standard dedicated to provide video or audio services for handheld terminals. On the satellite part, this standard can make use of interleaving mechanisms to mitigate the effects of the Land Mobile Satellite channel. As a result, these mechanisms enable the in-time distribution of a codeword over a duration ranging from 100 ms to about 30 s, depending on their parameters. This mechanism significantly improves the error recovery performance of the code; however in the literature, a theoretical evaluation at system level of this improvement is missing. Moreover, carrying out Monte-Carlo simulations implementing real decoding processes on significant traveled distances is time prohibitive.
We propose hereafter a prediction method compatible with fast simulations to quantitatively evaluate the system performance in terms of Rate, Erroneous Second Ratio, and zapping time. This method is based on the computation of the mutual information between emitted and received symbols for QPSK modulation and turbo coding.
We demonstrate that our method reaches a prediction precision of the order of 0.1 dB, which is significantly better than two classical prediction methods. Moreover, our solution reduces the simulation time by a factor of 500 compared with Monte-Carlo. Beyond DVB-SH application, the presented approach can be applied in a large panel of satellite mobile systems and is completely new for the satellite community
SH-CA data & code.zip
No full textSH-CA: spatial hierarchical learning based cellular automata for simulating urban expansion by aggregating multiscale neighborhood effect</p
Adapting DVB-SH system parameters to mobile environments
Full text linkA performance analysis of the digital video broadcasting
- satellite to handheld (DVB-SH) system in presence of ground mobile terminals (GMTs) is presented. The paper focuses on the Doppler spread issue. Indeed, the mobility of
GMTs induces a Doppler spread in the orthogonal frequency
division multiplexing (OFDM) signal that destroys the orthogonality of subcarriers. The loss of orthogonality produces inter-carrier interference (ICI) and hence a degradation of the system performance in terms of symbol error probability. The paper presents the conditions in which this degradation can be compensated for by an increase in the signal to noise ratio (SNR) at the receiver side. The result depends on both the modulation scheme and the speed of GMTs. Inversely, having a maximum allowable margin on the received SNR allows us to determine an upper bound on the mobile station velocity
SH-Struct: An Affirmative Advanced Method for Mining Frequent Patterns
No full textData Mining requires versatile computational techniques for analyzing patterns among large and diversified databases. One of the most influential and typically emerging research area is to develop impinging structures for valid frequent patterns. In this paper, we have formulated a novel data structure known as SH-Struct (Soft-Hyperlinked Structure) which mines the complete frequent itemset using SH-Mine algorithm. This algorithm enables frequent pattern mining with different supports. Fundamentally, SH-Struct is a tree structure which maintains H-Struct (Hyperlinked Structure) at each level of the tree called SH-Tree to improvise storage compression and reserves frequent patterns very fast using SH-Mine algorithm. To validate the effectiveness of our structure here we present the performance study of SH-mine and FP (Frequent Pattern)- growth algorithm highlighting space and time payoffs for two categories of databases: sparse and dense. The experimental results show the prominent behavior of proposed method and incite us to further deploy it in more dense and dynamic databases such as temporal databases for generating more prognostic outcomes. </p
Generic approach for hierarchical modulation performance analysis: application to DVB-SH
Full text linkBroadcasting systems have to deal with channel diversity in order to offer the best rate to the users. Hierarchical
modulation is a practical solution to provide several rates in function of the channel quality. Unfortunately the performance evaluation of such modulations requires time consuming simulations. We propose in this paper a novel approach based on the channel capacity to avoid these simulations. The method allows to study the performance in terms of spectrum efficiency of hierarchical and also classical modulations combined with error correcting codes. Our method will be applied to the DVB-SH standard which considers hierarchical modulation as an optional feature
Differentiation of SH-SY5Y neuroblastoma cells using retinoic acid and BDNF: A model for neuronal and synaptic differentiation in neurodegeneration
Full text linkThere has been much interest in the use of cell culture models of neurones, to avoid the animal welfare and cost issues of using primary and human-induced pluripotent stem cell (hiPSC)-derived neurones respectively. The human neuroblastoma cell line, SH-SY5Y, is extensively used in laboratories as they can be readily expanded, are of low cost and can be differentiated into neurone-like cells. However, much debate remains as to their phenotype once differentiated, and their ability to recapitulate the physiology of bona fide neurones. Here, we characterise a differentiation protocol using retinoic acid and BDNF, which results in extensive neurite outgrowth/branching within 10 days, and expression of key neuronal and synaptic markers. We propose that these differentiated SH-SY5Y cells may be a useful substitute for primary or hiPSC-derived neurones for cell biology studies, in order to reduce costs and animal usage. We further propose that this characterised differentiation timecourse could be used as an in vitro model for neuronal differentiation, for proof-of principle studies on neurogenesis, e.g. relating to neurodegenerative diseases. Finally, we demonstrate profound changes in Tau phosphorylation during differentiation of these cells, suggesting that they should not be used for neurodegeneration studies in their undifferentiated state
Mathematical Models of Neuronal Excitability: A Theoretical Approach to SH-SY5Y Cells
No full textreservedanalisi dei modelli matematici, ideati per la comunicazione neuronale con successiva applicazione alle cellule staminali SH-SY5YAnalysis of mathematical models for neuronal communication and their application to SH-SY5Y stem cells
Application of P & SH-waves for rock anisotropy studies: Genting Highlands case study
No full textSeismic refraction surveys utilizing P & SH-waves were carried out over an abandoned quarry
at Genting Highlands in order to study the anisotropy of the bedrock of that site. Shear (S) and
compression (P) acoustic velocities of the subsurface refractor have shown significant variations in their
spatial distribution. These variations in velocity values were compiled and then qualitatively correlated
with surface fracture surveys conducted during the course of acquiring the field data.
Seismic P & SH-wave velocity values obtained from in situ measurements have been used for
calculating the anisotropy percentage and slowness factor. The petrophysical parameters computed are
then contoured to identify the orientation of fracture zones along the refractor surface
Prediction of performance of the DVB-SH system relying on mutual information
Full text linkDVB-SH (Digital Video Broadcasting-Satellite Handled) is a broadcasting standard dedicated to hybrid broadcasting systems combining a satellite and a terrestrial part. On the satellite part, dedicated interleaving and time slicing mechanisms are proposed to mitigate the effects of Land Mobile Satellite (LMS) channel, based on a convolutional interleaver. Depending on the parameters of this interleaver, this mechanism enables to split in time a codeword on duration from 100 ms to about 30s. This mechanism signi?cantly improves the error recovery performance of the code but in literature, exact evaluation at system level of this improvement is missing. The objective of this paper is to propose a prediction method compatible with fast simulations, to quantitatively evaluate the system performance in terms of Packet Error Rate (PER). The main dif?culty is to evaluate the decoding probability of a codeword submitted to several levels of attenuation. The method we propose consists in using as metric the Mutual Information (MI) between coded bit at the emitter side and the received symbol. It is shown that, by averaging the MI over the codeword and by using the decoding performance function g such that PER=g(MI)determined on the Gaussian channel, we can signi?cantly improve the precision of the prediction compared to the two other methods based on SNR and Bit Error Rate (BER). We evaluated these methods on three arti?cial channels where each codeword is transmitted with three or four different levels of attenuations. The prediction error of the SNR-based (resp. the input BER-based) method varies from 0.5 to 1.7 dB (resp. from 0.7 to 1.2 dB) instead of the MI-based method achieves a precision in the order of 0.1 dB in the three cases. We then evaluate this method on real LMS channels with various DVB-SH interleavers and show that the instantaneous PER can also be predicted with high accuracy
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