Performance of Optimum Combining in a Poisson Field of Interferers and Rayleigh Fading Channels

This paper studies the performance of antenna array processing in distributed multiple access networks without power control. The interference is represented as a Poisson point process. Desired and interfering signals are subject to both path-loss fading (with an exponent greater than 2) and to independent Rayleigh fading. Using these assumptions, we derive the exact closed form expression for the cumulative distribution function of the output signal-to-interference-plus-noise ratio when optimum combining is applied. This results in a pertinent measure of the network performance in terms of the outage probability, which in turn provides insights into the network capacity gain that could be achieved with antenna array processing. We present and discuss examples of applications, as well as some numerical results.Comment: Submitted to IEEE Trans. on Wireless Communication (Jan. 2009

Analyse du potentiel des techniques de traitement de signal avancées dans les réseaux AD HOC

Résumé Un réseau ad hoc mobile est un réseau formé par un ensemble d'unités sans fil et mobiles sans l'aide d'une infrastructure préétablie. La caractéristique fondamentale des réseaux ad hoc mobiles est que les conditions dans lesquelles ils subsistent sont hautement dynamiques. La qualité des communications est limitée par les phénomènes physiques d'évanouissement de signal et les interférences provenant de l'accès simultané à l'interface radio. Généralement, les études des réseaux ad hoc sont menées avec une abstraction simplifiée de la couche physique. Ainsi, les performances du réseau sont surestimées par rapport aux conditions réelles. D'un autre côté, elles sont sous-estimées du fait qu'on ne considère pas complètement les stratégies offertes par la couche physique. Le travail mené durant la thèse consiste à répondre à la problématique suivante: quels sont les limites et les apports des techniques de traitement de signal avancées sur la capacité et les performances des réseaux ad hoc? La modélisation de l'interférence dans un environnement dynamique et décentralisé est complexe. Dans la littérature, plusieurs modèles tentent de simplifier ou même de négliger les phénomènes de la couche physique. Dans cette thèse, nous avons considéré un modèle relativement récent dans la littérature et qui découle de la théorie de la géométrie stochastique. Ce type de modélisation permet d'incorporer les effets de la propagation radio à petite et à grande échelle et surtout les différentes technologies de détection et de traitement de signal. Dans la première partie de ce travail, nous avons identifié des techniques de traitement de signal qui ont le potentiel de remédier au problème de l'interférence. Précisément, nous avons considéré l'analyse de la technique de soustraction successive de l'interférence et la technologie des antennes multiples. Ce travail a abouti à des résultats analytiques qui expriment directement la qualité des liens entre les paires émetteur-récepteur en fonction, d'une part, des configurations du réseau, en termes du nombre d'unités, du type et de la charge du trafic des données ainsi que de la qualité de service minimale exigée, et d'autre part, des caractéristiques de la couche physique en termes des paramètres de l'environnement de propagation et du type du détecteur utilisé. Ces résultats analytiques permettent de quantifier l'amélioration du rapport signal à interférence plus bruit procurée en fonction du nombre d'antennes utilisées et de l'algorithme de traitement de signal appliqué. Ainsi, ces résultats relient les paramètres de la couche physique aux paramètres des couches supérieures. Dans la deuxième partie de ce travail, nous avons élaboré une étude des performances de stratégies de communication opportunistes, et ce à partir des résultats développés dans la première partie. Cette étude a mené à une quantification des performances des approches opportunistes en termes de débit et de délai du réseau. Les résultats analytiques ont permis entre autre d'identifier les valeurs des paramètres du réseau qui aboutissent à son mode de fonctionnement optimal, c'est-à-dire des valeurs qui permettent de minimiser le délai moyen et de maximiser le débit global des communications.----------Abstract In wireless communications energy and spectrum resources are scarce and expensive, they must be efficiently managed to address the growing requirement of emerging applications. Intensive works have been dedicated to develop advanced processing technologies to improve the spectral efficiency. In decentralized multiple access system such as ad hoc network, interference represents the major performance inhibitor. Thus interference mitigating is one of the major research subjects in recent years. Several solutions have been proposed that consists on exploiting the particular structure of the interference which depends on the physical layer used. In fact, technologies like spread spectrum and multiple antennas provide a number of degrees of freedom that when properly exploited increase the system tolerance to interference. This thesis address the issue of quantifying the performance gain that can be achieved by using advanced signal processing technologies in the context of Ad Hoc networks, namely, interference cancellation and adaptive antenna array systems. In the context of spread spectrum different multiuser receiver schemes was introduced. The well known Minimum Mean Square Error, MMSE, is the multiuser receiver that maximizes the Signal to Interference plus Noise Ratio, SINR. The equivalent solution in the context of antenna array is known as Optimum Combining, OC, receiver. Studying the reliability of this receiver is an important issue and has been the subject of extensive work in the literature. Despite this, there is still much work to do to understand their limits in many contexts. In the first part, we derive the outage probability for the interference cancellation receiver and the optimum combining receiver. In the second part we establish an analysis of a number of opportunistic routing strategies and we quantify the performance gains achieved by employing adaptive antenna array systems in a multi-hop network

Investigation and Modeling of Electrical Stunning Parameters of Turkey Using Response Surface Methodology

Abstract: The aim of this work is to evaluate the effects of electrical stunning parameters of turkey on the quality of steak and stew using the response surface methodology. 1584 turkeys were used for the study. The parameters tested were the voltage and pulse. The responses were the sensory quality of steak and stew. The rejection rate varies between 0.23% (steak female) and 56.06% (female stew). Results show that it is possible to obtain a low rejection rates (< 1% for the steak of male turkey) at a voltage of 50 Volts and pulse of 7. In comparison of pulse, voltage remains the most important factor. The optimal conditions selected for the total output of the process obtained from the analysis of the response surfaces are: voltage, from 45 to 47 Volts; pulse from 6.5 to 7 and voltage from 50 to 52 Volts; pulse from 6.8 to 7, respectively for female and male turkeys. Under these experimental conditions, the rejection rates range from 0.23% to 0.80% and from 11.93% to 13.27% respectively for steak and stew. The results show that the voltage and pulse are both the parameters meaning on the global quality of steak and stew

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation

One of the ways in which legal services are financed, and indeed shaped, is through private insurance arrangement. Two contrasting types of legal expenses insurance contracts (LEI) seem to dominate in Europe: before the event (BTE) and after the event (ATE) legal expenses insurance. Notwithstanding institutional differences between different legal systems, BTE and ATE insurance arrangements may be instrumental if government policy is geared towards strengthening a market-oriented system of financing access to justice for individuals and business. At the same time, emphasizing the role of a private industry as a keeper of the gates to justice raises issues of accountability and transparency, not readily reconcilable with demands of competition. Moreover, multiple actors (clients, lawyers, courts, insurers) are involved, causing behavioural dynamics which are not easily predicted or influenced. Against this background, this paper looks into BTE and ATE arrangements by analysing the particularities of BTE and ATE arrangements currently available in some European jurisdictions and by painting a picture of their respective markets and legal contexts. This allows for some reflection on the performance of BTE and ATE providers as both financiers and keepers. Two issues emerge from the analysis that are worthy of some further reflection. Firstly, there is the problematic long-term sustainability of some ATE products. Secondly, the challenges faced by policymakers that would like to nudge consumers into voluntarily taking out BTE LEI

Search for stop and higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top-quark (stop) and the Higgs boson (higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 inverse femtobarns of proton-proton collision data at sqrt(s) = 8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the stop mass below 360 to 410 GeV, depending on the higgsino mass

Severe early onset preeclampsia: short and long term clinical, psychosocial and biochemical aspects

Preeclampsia is a pregnancy specific disorder commonly defined as de novo hypertension and proteinuria after 20 weeks gestational age. It occurs in approximately 3-5% of pregnancies and it is still a major cause of both foetal and maternal morbidity and mortality worldwide1. As extensive research has not yet elucidated the aetiology of preeclampsia, there are no rational preventive or therapeutic interventions available. The only rational treatment is delivery, which benefits the mother but is not in the interest of the foetus, if remote from term. Early onset preeclampsia (<32 weeks’ gestational age) occurs in less than 1% of pregnancies. It is, however often associated with maternal morbidity as the risk of progression to severe maternal disease is inversely related with gestational age at onset2. Resulting prematurity is therefore the main cause of neonatal mortality and morbidity in patients with severe preeclampsia3. Although the discussion is ongoing, perinatal survival is suggested to be increased in patients with preterm preeclampsia by expectant, non-interventional management. This temporising treatment option to lengthen pregnancy includes the use of antihypertensive medication to control hypertension, magnesium sulphate to prevent eclampsia and corticosteroids to enhance foetal lung maturity4. With optimal maternal haemodynamic status and reassuring foetal condition this results on average in an extension of 2 weeks. Prolongation of these pregnancies is a great challenge for clinicians to balance between potential maternal risks on one the eve hand and possible foetal benefits on the other. Clinical controversies regarding prolongation of preterm preeclamptic pregnancies still exist – also taking into account that preeclampsia is the leading cause of maternal mortality in the Netherlands5 - a debate which is even more pronounced in very preterm pregnancies with questionable foetal viability6-9. Do maternal risks of prolongation of these very early pregnancies outweigh the chances of neonatal survival? Counselling of women with very early onset preeclampsia not only comprises of knowledge of the outcome of those particular pregnancies, but also knowledge of outcomes of future pregnancies of these women is of major clinical importance. This thesis opens with a review of the literature on identifiable risk factors of preeclampsia