Dynamic Retransmission Limit Scheme in MAC Layer for Routing in Multihop Ad hoc Networks

We consider a wireless ad hoc network with random access channel. We present a model that takes into account topology, routing, random access in MAC layer, and forwarding probability. In this paper, we focus on drawing benefit from the interaction of the MAC (governed by IEEE 802.11 or slotted Aloha) and routing by defining a new cross-layer scheme for routing based on the limit number of retransmission. By adjusting dynamically and judiciously this parameter in a saturated network, we have realized that both stability of forwarding queues and average throughput are significantly improved in linear networks with symmetric traffic: a gain of 100% can be reached. While in asymmetric topology network with asymmetric traffic, we achieve a better average delay (resp., throughput) for each connection without changing the average throughput (resp., delay). In addition, we show the efficiency of our new scheme in case of multimedia applications with delay constraint. A detailed performance study is presented using analytical and simulation evaluation

Bladder Metastasis of Gastric Adenocarcinoma

Teaching point: Metastatic involvement has to be considered in the differential diagnosis for diffuse bladder wall thickenin

Current Priorities for Public Health Practice in Addressing the Role of Human Genomics in Improving Population Health

In spite of accelerating human genome discoveries in a wide variety of diseases of public health significance, the promise of personalized health care and disease prevention based on genomics has lagged behind. In a time of limited resources, public health agencies must continue to focus on implementing programs that can improve health and prevent disease now. Nevertheless, public health has an important and assertive leadership role in addressing the promise and pitfalls of human genomics for population health. Such efforts are needed not only to implement what is known in genomics to improve health but also to reduce potential harm and create the infrastructure needed to derive health benefits in the future

The Scientific Foundation for Personal Genomics: Recommendations from a National Institutes of Health–Centers for Disease Control and Prevention Multidisciplinary Workshop

The increasing availability of personal genomic tests has led to discussions about the validity and utility of such tests and the balance of benefits and harms. A multidisciplinary workshop was convened by the National Institutes of Health and the Centers for Disease Control and Prevention to review the scientific foundation for using personal genomics in risk assessment and disease prevention and to develop recommendations for targeted research. The clinical validity and utility of personal genomics is a moving target with rapidly developing discoveries but little translation research to close the gap between discoveries and health impact. Workshop participants made recommendations in five domains: (1) developing and applying scientific standards for assessing personal genomic tests; (2) developing and applying a multidisciplinary research agenda, including observational studies and clinical trials to fill knowledge gaps in clinical validity and utility; (3) enhancing credible knowledge synthesis and information dissemination to clinicians and consumers; (4) linking scientific findings to evidence-based recommendations for use of personal genomics; and (5) assessing how the concept of personal utility can affect health benefits, costs, and risks by developing appropriate metrics for evaluation. To fulfill the promise of personal genomics, a rigorous multidisciplinary research agenda is needed

Evaluation des performances dans les réseaux ad hoc sans fils

Dans cette thèse, nous nous focalisons sur la caractérisation des performances des réseaux ad hoc à accès aléatoire au canal en utilisant des paramètres de plusieurs couches avec aptitude de transfert d'information. Les métriques de performances qui nous intéressent sont la stabilité des files d'attentes de transfert, le débit, le délai et la consommation d'énergie. Principalement, la compréhension de l'interaction entre les couches MAC/PHY et routage, d'une part, et l'interaction des noeuds entre eux pour cause d'interférences, d'autre part, constituent le centre de notre travail. Cette thèse est divisée en deux parties. Dans la première partie, nous proposons et évaluons un nouveau protocole de routage entre-couche prenant en compte la consommation d'énergie dans le protocole OLSR. Nos simulations sont importantes pour la compréhension du réel impact des couches MAC/PHY non idéales sur le routage. Les résultats montrent que les approches de routages qui ne prennent pas en compte les effets des basses couches doivent être révisées.Dans la deuxièmement partie, nous avons basé notre étude sur un modèle analytique qui prend en compte la topologie, le routage, l'accès aléatoire dans la couche MAC et une probabilité de transfert. Nous distinguons trois propriétés clés du réseau qui font que notre contribution dans cette thèse est nouvelle si elles sont considérées ensemble. La première est l'ordonnancement des paquets dans la couche réseau. En utilisant un ordonnancement WFQ (Weighted fair queueing), nous avons principalement étudié l'impact de la coopération et la région de stabilité dans le réseau. Cette dernière est aussi caractérisée dans le cas d'un réseau hybride, où un réseau ad hoc est interconnecté avec un autre cellulaire. La deuxième est l'asymétrie du réseau ad hoc en termes de topologie, trafic et paramètres des noeuds. Cependant, une étude sur un réseau à une seule dimension est aussi réalisée. En développant le modèle du réseau, nous sommes arrivés à un modèle analytique avec le IEEE 802.11e DCF dans le contexte d'un réseau ad hoc multi-sauts. Le taux d'accès au canal et la probabilité de collision sont maintenant exprimés en fonction de l'intensité du trafic, de la topologie, et du routage. La troisième est le nombre limite de retransmissions dans la couche MAC dédié pour chaque connexion. D'une part, ce dernier est responsable de l'asymétrie du taux de service des files d'attentes et de la distribution générale du temps de service. D'autre part, il a un impact direct sur les performances d'un réseau chargé. Nous avons pu bénéficier de l'interaction de la couche MAC et routage en définissant un nouveau mécanisme entre-couche basé sur le nombre limite de retransmissions. Des résultats numériques et des simulations sont présents pour assister et confirmer notre travailThis thesis focuses on the characterization of random access ad hoc networks performance using multi-layer parameters and forwarding capability. The performance metrics of interest are stability of forwarding queues, throughput, delay and energy consumption. Mainly, the comprehension of the interactions between the MAC/PHY layers and the network layer, on the one hand, and the interactions among all nodes due to interferences, on the other hand, are in the center of this thesis. This dissertation is divided in two parts. In the first part, we propose and evaluate a new cross-layer energy power-aware routing protocol. Our simulations were important to understand the real impact of a non-ideal MAC/PHY layers on routing. The results show that routing approaches that do not account for lower layers impact have to be revised. In the second part, we based our study on an analytical model that takes into account topology, routing, random access in MAC layer and forwarding probability. We distinguish three key features of the network model that make our contribution in this thesis novel when considered together. The first one is packet scheduling in the network layer. Using a weighted fair queueing, we mainly studied the cooperation effect and the stability region in the network. This latter was also characterized in an hybrid network when interconnecting ad hoc and cellular networks. The second one is the asymmetry of the ad hoc network in terms of topology, traffic and nodes' parameters. Nevertheless, one dimensional study is also presented. By developing the network model, we reached a new analytical modeling of the IEEE 802.11e DCF in the context of multi-hop ad hoc networks. The attempt rate and collision probability are now function of the traffic intensity, on topology and on routing decision. The third one is the finite limit number of retransmissions in MAC layer dedicated to each connection. On the one hand, this latter is responsible for asymmetric queue service rate and for getting a general service time distribution. On the other hand, it has a direct impact on the performance of a loaded network. Finally, we got benefit from the interaction of the MAC and routing by defining a new cross-layer scheme for routing based on the limit number of retransmissions. Numerical results and simulations are presented to assist and confirm our workAVIGNON-BU Centrale (840072102) / SudocSudocFranceF

Acknowledgement

All my thanks is for our father in heaven for his eternal love to us. I would like to thank Eitan, my supervisor, for his many suggestions and constant support during this small research. I am also thankful for the two Lebanese of the team Ahmad and Sara for they have been a support to me, and they encourage me on the road of the research. My companion of the office, Urtzi, was my example in the manner he works. I thank him, because he was gentle and a man of peace. I thank Bala for he helped me in his knowledge, and he was present to listen to me. I thank Tania for she was always smiling, and present in the critical situations. Each day my first good morning was to Florence, I wish to here good days full of graces. It was a pleasure to me to meet Robin. I thank all the persons on the team and specially the chief Philippe, for he guides the team in an intelligent manner