Exact balanced random imputation for sample survey data

Surveys usually suffer from non-response, which decreases the effective sample size. Item non-response is typically handled by means of some form of random imputation if we wish to preserve the distribution of the imputed variable. This leads to an increased variability due to the imputation variance, and several approaches have been proposed for reducing this variability. Balanced imputation consists in selecting residuals at random at the imputation stage, in such a way that the imputation variance of the estimated total is eliminated or at least significantly reduced. In this work, we propose an implementation of balanced random imputation which enables to fully eliminate the imputation variance. Following the approach in Cardot et al. (2013), we consider a regularized imputed estimator of a total and of a distribution function, and we prove that they are consistent under the proposed imputation method. Some simulation results support our findings

Prediction of performance of the DVB-SH system relying on mutual information

DVB-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

Etude des filtres LPTV numériques : applications aux communications numériques

Les filtres linéaires périodiques (LPTV) ont fait l'objet de divers travaux au sein du laboratoire TéSA. Cette famille de filtres n'y a cependant été envisagée que sous la forme analogique. Ce travail de thèse propose en premier lieu une étude théorique des filtres LPTV numériques. Dans un second temps, l'intérêt de l'utilisation des filtres LPTV numériques pour les communications numériques est considéré. Après avoir recensé les applications existantes, nous proposons alors plusieurs applications des filtres LPTV. La partie théorique formalise les différentes représentations LPTV et propose d'établir un rapprochement entre le domaine du traitement multicadence et les filtres LPTV. A cet effet, une relation d'équivalence entre filtres LPTV et bancs de filtres à décimation maximale est définie. Le problème de l'inversibilité des filtres LPTV est ensuite abordé. La littérature étant pauvre en méthodes de construction de filtres LPTV inversibles, nous définissons deux familles de filtres LPTV ayant cette propriété. La dernière partie théorique s'intéresse à un cas particulier de filtres LPTV que sont les changements d'horloge périodiques (PCC). Il y est montré que l'ensemble de ces transformations est confondu avec l'ensemble des entrelaceurs périodiques. S'il est vrai que les PCC constituent un sujet somme toute marginal, ce dernier résultat permet de proposer une nouvelle approche et de nouveaux outils pour l'étude des entrelaceurs, outil largement utilisé dans les communications numériques. Dans le deuxième volet, nous proposons plusieurs applications de filtres LPTV pour les communications numériques. Les filtres LPTV sont tout d'abord proposés comme outil pour la réduction du Peak Average Power Ratio (PAPR) pour les systèmes OFDM (Orthogonal Frequency Division Multiplexing). Les performances théoriques en Taux d'Erreur Binaire (TEB) sont dans ce contexte étudiées dans le cas d'un canal sélectif en fréquence pour les filtres LPTV utilisés. Nous proposons aussi l'utilisation des filtres LTPV pour réaliser de l'étalement de spectre. Dans cette optique, un système d'accès multiple est décrit reposant sur une méthode de construction d'une famille de filtres LPTV orthogonaux à partir d'un filtre LPTV générateur. ABSTRACT : This work is divided into two main parts. The first one is devoted to a theoretical study of digital LPTV filters. Emphasis is first laid on different representations of LPTV filters. In addition, Maximally Decimated Filter Banks are related to LPTV filters. Through these results, we propose a construction method to achieve invertible LPTV filters. The second part is then devoted to applications of LPTV filters in a digital communications framework. After describing a state of the art, we propose then the use of LPTV filters for Peak to Average Power Ratio Reduction in an OFDM context. In a multiuser system framework, we also propose a method to achieve orthogonal LPTV filters. We then take the most of these results to achieve a Spread Spectrum Multiuser System. Performances of this system are considered in term of Bir Error Rate

Influence of an irregular sampling on reconstruction performances

Cet article étudie diverses méthode de reconstruction d'un processus à spectre borné dans le cas d'un échantillonnage périodique et d'un échantillonnage irrégulier. Trois méthodes différentes dans le cas d'un échantillonnage irrégulier(interpolation par splines, méthode dite matricielle et formule de Lagrange modifiée) sont comparées du point de vue des performances en reconstruction. L'influence d'une composante spectrale en dehors de la bande de Shannon est également étudiée. Tous ces résultats sont comparés au cas d'un échantillonnage régulier. Lorsque la condition de Shannon est vérifiée, la formule de Lagrange modifiée en présence de gigue donne des résultats similaires à la formule de Shannon pour un échantillonnage régulier. Dans le cas contraire, l'échantillonnage non-périodique permet d'étaler les interférences hors bande utile

Étude des filtres LPTV numériques (applications aux communications numériques)

TOULOUSE-ENSEEIHT (315552331) / SudocSudocFranceF

Procédé de réception et récepteur pour transmission numérique série codée sur un canal non stationnaire

L'invention concerne un procédé de réception de données sur un canal série bruité à atténuation non stationnaire dans lequel au moins une valeur représentative d'un taux d'erreurs ER du flux reçu de bits est élaborée sans réalisation du décodage. Une valeur d'information mutuelle I est élaborée (34) selon une fonction prédéterminée de la qualité de transmission Q , et une moyenne d'information mutuelle est élaborée (35) sur chaque mot codé reçu, puis au moins une valeur du taux d'erreurs ER du flux reçu de bits est élaborée (38) à partir de chaque valeur de la moyenne d'information mutuelle par utilisation d'une fonction standard prédéterminée sur un canal à bruit blanc gaussien additif

Procédé et dispositif d'évaluation d'une transmission numérique série codée sur un canal non stationnaire

L'invention concerne un procédé d'évaluation des performances d'une transmission numérique série codée et modulée sur un canal série bruité à atténuation non stationnaire dans lequel au moins une valeur représentative d'un taux d'erreurs ER du flux reçu de bits est élaborée sans réalisation du décodage. Une valeur d'information mutuelle I est élaborée (34) selon une fonction prédéterminée de la qualité de transmission Q , et une moyenne d'information mutuelle est élaborée (35) sur chaque mot codé reçu, puis au moins une valeur du taux d'erreurs ER du flux reçu de bits est élaborée (38) à partir de chaque valeur de la moyenne d'information mutuelle par utilisation d'une fonction standard prédéterminée sur un canal à bruit blanc gaussien additif. Elle s'étend à un dispositif, un produit logiciel, et un support d'enregistrement pour la mise en œuvre de ce procédé

Synchronization algorithm for LPTV-based spread spectrum signals

Linear Periodic Time-Varying (LPTV) filters can be used as a Spread Spectrum (SS) technique. A particular case of such spreading LPTV filters are Periodic Clock Changes (PCCs). When the spreading operation is realized with PCCs, the synchronization algorithm can also be considered as an LPTV problem. In this paper we will focus on the early-late Delay Lock Loop (DLL) algorithm. We show that this technique can be used to achieve synchronization when the spreading operation is realized by a special class of PCCs: matrix interleavers

Quantitative Signal Intensity in Fluid-Attenuated Inversion Recovery and Treatment Effect in the WAKE-UP Trial

International audienceBackground and Purpose— Relative signal intensity of acute ischemic stroke lesions in fluid-attenuated inversion recovery (fluid-attenuated inversion recovery relative signal intensity [FLAIR-rSI]) magnetic resonance imaging is associated with time elapsed since stroke onset with higher intensities signifying longer time intervals. In the randomized controlled WAKE-UP trial (Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke Trial), intravenous alteplase was effective in patients with unknown onset stroke selected by visual assessment of diffusion weighted imaging fluid-attenuated inversion recovery mismatch, that is, in those with no marked fluid-attenuated inversion recovery hyperintensity in the region of the acute diffusion weighted imaging lesion. In this post hoc analysis, we investigated whether quantitatively measured FLAIR-rSI modifies treatment effect of intravenous alteplase. Methods— FLAIR-rSI of stroke lesions was measured relative to signal intensity in a mirrored region in the contralesional hemisphere. The relationship between FLAIR-rSI and treatment effect on functional outcome assessed by the modified Rankin Scale (mRS) after 90 days was analyzed by binary logistic regression using different end points, that is, favorable outcome defined as mRS score of 0 to 1, independent outcome defined as mRS score of 0 to 2, ordinal analysis of mRS scores (shift analysis). All models were adjusted for National Institutes of Health Stroke Scale at symptom onset and stroke lesion volume. Results— FLAIR-rSI was successfully quantified in stroke lesions in 433 patients (86% of 503 patients included in WAKE-UP). Mean FLAIR-rSI was 1.06 (SD, 0.09). Interaction of FLAIR-rSI and treatment effect was not significant for mRS score of 0 to 1 ( P =0.169) and shift analysis ( P =0.086) but reached significance for mRS score of 0 to 2 ( P =0.004). We observed a smooth continuing trend of decreasing treatment effects in relation to clinical end points with increasing FLAIR-rSI. Conclusions— In patients in whom no marked parenchymal fluid-attenuated inversion recovery hyperintensity was detected by visual judgement in the WAKE-UP trial, higher FLAIR-rSI of diffusion weighted imaging lesions was associated with decreased treatment effects of intravenous thrombolysis. This parallels the known association of treatment effect and elapsing time of stroke onset

Functional Outcome of Intravenous Thrombolysis in Patients With Lacunar Infarcts in the WAKE-UP Trial

Importance: The rationale for intravenous thrombolysis in patients with lacunar infarcts is debated, since it is hypothesized that the microvascular occlusion underlying lacunar infarcts might not be susceptible to pharmacological reperfusion treatment. Objective: To study the efficacy and safety of intravenous thrombolysis among patients with lacunar infarcts. Design, Setting, and Participants: This exploratory secondary post hoc analysis of the WAKE-UP trial included patients who were screened and enrolled between September 2012 and June 2017 (with final follow-up in September 2017). The WAKE-UP trial was a multicenter, double-blind, placebo-controlled randomized clinical trial to study the efficacy and safety of intravenous thrombolysis with alteplase in patients with an acute stroke of unknown onset time, guided by magnetic resonance imaging. All 503 patients randomized in the WAKE-UP trial were reviewed for lacunar infarcts. Diagnosis of lacunar infarcts was based on magnetic resonance imaging and made by consensus of 2 independent investigators blinded to clinical information. Main Outcomes and Measures: The primary efficacy variable was favorable outcome defined by a score of 0 to 1 on the modified Rankin Scale at 90 days after stroke, adjusted for age and severity of symptoms. Results: Of the 503 patients randomized in the WAKE-UP trial, 108 patients (including 74 men [68.5%]) had imaging-defined lacunar infarcts, whereas 395 patients (including 251 men [63.5%]) had nonlacunar infarcts. Patients with lacunar infarcts were younger than patients with nonlacunar infarcts (mean age [SD], 63 [12] years vs 66 [12] years; P = .003). Of patients with lacunar infarcts, 55 (50.9%) were assigned to treatment with alteplase and 53 (49.1%) to receive placebo. Treatment with alteplase was associated with higher odds of favorable outcome, with no heterogeneity of treatment outcome between lacunar and nonlacunar stroke subtypes. In patients with lacunar strokes, a favorable outcome was observed in 31 of 53 patients (59%) in the alteplase group compared with 24 of 52 patients (46%) in the placebo group (adjusted odds ratio [aOR], 1.67 [95% CI, 0.77-3.64]). There was 1 death and 1 symptomatic intracranial hemorrhage according to Safe Implementation of Thrombolysis in Stroke-Monitoring Study criteria in the alteplase group, while no death and no symptomatic intracranial hemorrhage occurred in the placebo group. The distribution of the modified Rankin Scale scores 90 days after stroke also showed a nonsignificant shift toward better outcomes in patients with lacunar infarcts treated with alteplase, with an adjusted common odds ratio of 1.94 (95% CI, 0.95-3.93). Conclusions and Relevance: While the WAKE-UP trial was not powered to demonstrate the efficacy of treatment in subgroups of patients, the results indicate that the association of intravenous alteplase with functional outcome does not differ in patients with imaging-defined lacunar infarcts compared with those experiencing other stroke subtypes.status: publishe