During the last decade, relay networks have attracted a lot of interest due to their numerous benefits. The relaying technique allows extending the coverage zone of wireless networks and offers a higher reliability for communication systems. The performance of relay networks can be improved further by the use of automatic repeat request (ARQ) and hybrid automatic repeat request (HARQ) techniques. ARQ and HARQ are retransmission mechanisms that ensure a good quality of service even in absence of channel state information at the transmitter. We, firstly, study the spectral and energy efficiency of ARQ in Nakagami-m block-fading channels. We maximize both spectral efficiency and energy efficiency with respect to the transmitted power. We derive exact expressions as well as compact and tight approximation for the solutions of these problems. Our analysis shows that the two problems of maximizing spectral efficiency and energy efficiency with respect to the transmitted power are completely different and give different solutions. Additionally, operating with a power that maximizes energy efficiency can lead to a significant drop in the spectral efficiency, and vice versa. Next, we consider a three node relay network comprising a source, a relay, and a destination. The source transmits the message to the destination using HARQ with incremental redundancy (IR). The relay overhears the transmitted message, amplifies it using a variable gain amplifier, and then forwards the message to the destination. This latter combines both the source and the relay message and tries to decode the information. In case of decoding failure, the destination sends a negative acknowledgement. A new replica of the message containing new parity bits is then transmitted in the subsequent HARQ round. This process continues until successful decoding occurs at the destination or a maximum number M of rounds is reached. We study the performance of HARQ-IR over the considered relay channel from an information theoretic perspective. We derive exact expressions and bounds for the information outage probability, the average number of transmissions, and the average transmission rate. Moreover, we evaluate the delay experienced by Poisson arriving packets over the considered relay network. We also provide analytical expressions for the expected waiting time, the sojourn time, and the energy efficiency. The derived exact expressions are validated by Monte Carlo simulations. Finally, we consider a relay network consisting of a source, K relays, and a destination. The source transmits a message to the destination using HARQ-IR. We study the performance of HARQ-IR over dualhop multibranch amplify-and-forward relay channels. We derive exact expression for outage probability of the considered network. We investigate the benefit of relaying and the effect of changing the rate and the maximum number M of rounds on the outage probability.

Master of Science / Department of Computing and Information Sciences / Daniel A. Andresen / Increasing web content and Internet traffic is making web prediction models popular. A web prediction model helps to predict user requests ahead of time, making web servers more responsive. It caches these pages at the server side or pre-sends the response to the client to reduce web latency. Several prediction techniques have been tried in the past; Markov based prediction models being the most popular ones. Among these, the All-K[superscript]th -order Markov model has been found to be most effective. In this project, a Markov tree is designed, which is a fourth order model but behaves like an All-K[superscript]th-order Markov model because of its ability to recognize different order models according to the height of the tree. It has dual characteristics of good applicability and predictive accuracy. A Markov tree gives a complete description on the frequency with which a particular state occurs, and the number of times a path to a particular state is used, to access its child nodes. Further, the model can be pruned to eliminate states that have very little contribution towards the accuracy of the model. In this work, an evolutionary model is designed that makes use of a fitness function. The fitness function is a weighted sum of precision and the extent of coverage that the model offers. This helps to generate a model with reduced complexity. Results indicate that this model performs consistently with good predictive accuracy among different log files. The evolutionary approach helps to train the model to make predictions commensurate to current web browsing patterns.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Soft-decision correlation decoding with retransmission requests for block codes is proposed and the resulting performance is analyzed. The correlation decoding rule is modified to allow retransmission requests when the received word is rendered unreliable by the channel noise. The modification is realized by a reduction in the volume in Euclidean space of the decoding region corresponding to each codeword. The performance analysis reveals the typical throughput - reliability trade-off characteristic of error control systems which employ retransmissions. Performance comparisons with hard-decision decoding reveal performance improvements beyond those attainable with hard-decision decoding algorithms. The proposed soft-decision decoding rule permits the use of a simplified codeword searching algorithm which reduces the complexity of the correlation decoder to the point where practical implementation is feasible.

This thesis is concerned with caching algorithms. We investigate three variations of the caching problem: web caching in the Torng framework, relative competitiveness and caching with request reordering. <br /><br /> In the first variation we define different cost models involving page sizes and page costs. We also present the Torng cost framework introduced by Torng in [29]. Next we analyze the competitive ratio of online deterministic marking algorithms in the BIT cost model combined with the Torng framework. We show that given some specific restrictions on the set of possible request sequences, any marking algorithm is 2-competitive. <br /><br /> The second variation consists in using the relative competitiveness ratio on an access graph as a complexity measure. We use the concept of access graphs introduced by Borodin [11] to define our own concept of relative competitive ratio. We demonstrate results regarding the relative competitiveness of two cache eviction policies in both the basic and the Torng framework combined with the CLASSICAL cost model. <br /><br /> The third variation is caching with request reordering. Two reordering models are defined. We prove some important results about the value of a move and number of orderings, then demonstrate results about the approximation factor and competitive ratio of offline and online reordering schemes, respectively.

A SOA está se tornando uma abordagem difundida no desenvolvimento de sistemas. Em sistemas maiores onde se utiliza SOA pode ocorrer problemas de alta demanda, que podem ser resolvidos com arquiteturas distribuídas como clusters. Esta dissertação apresenta a proposta de uma nova arquitetura para distribuição de requisições em clusters de web services. A arquitetura proposta tem foco na distribuição flexível de requisições, possibilitando o emprego de políticas diversificadas, estas voltadas a diferentes objetivos, aplicações e plataformas. A arquitetura também propõe trabalhar de forma dinâmica, possibilitando decisões baseadas na coleta de estado dos elementos que compõem a estrutura de atendimento. A transparência, do ponto de vista do cliente, também é tratada na arquitetura. Os testes da arquitetura foram realizados através de um protótipo que a implementa. O protótipo instancia os objetivos propostos na arquitetura, apresentando ganhos de desempenho em relação à solução existente atualmente. A flexibilidade das políticas de distribuição é destacada através da construção de uma política, cujo objetivo é melhorar a eficiência no consumo de energia de clusters. Dentre as contribuições do trabalho está a criação de uma nova arquitetura de software que atua como facilitadora para a criação de políticas de distribuição de requisições mais eficiente para web services / SOA is becoming a widespread approach to develop systems. High demand problems may appear in huge systems where SOA and web services are used. This problems can be solved by means of distributed architectures like clusters. This work presents the proposal of a new architecture for request distribution in web service clusters. The proposed architecture provides flexible request distribution. It allows the use of several policies, these related to different objectives, applications and platforms. The architecture\'s dynamic feature enables decisions based on states of the cluster\'s elements, in a transparent way, under clients\' point of view. The architecture was tested using a prototype that implements the proposed ideas in this work. The objectives of the proposal were reached by the prototype and still shown performance improving in many cases, when comparing to an existing solution. The use of a novel policy, related to energetic efficiency for clusters, is also shown on the experiments related to flexibility. Among architecture\'s contributions is a novel software architecture that acts as a facility to create and to test more efficient web services policies

La médicalisation de la naissance et plus largement de la reproduction humaine s’accélère et nous assistons à la banalisation de la césarienne et à l’émergence des césariennes sur demandes maternelles, sans indication médicale. Chez les femmes qui demandent une césarienne pour accoucher, les craintes concernant le sexe et la sexualité sont manifestes, comme l’est la question de la maîtrise de soi et des événements. Mais quant est-il au plan latent ? Dans la continuité des travaux portant sur l’image du corps, du versant maternel du traumatisme de la naissance et de la psychosexualité féminine, je propose l’hypothèse suivante : l’accouchement est pour la femme une expérience singulière tant au regard des fonctions de la reproduction humaine qu’à celui de la sexualité féminine. À ce titre, il se situe au point de contact entre la clinique de la périnatalité, du devenir mère, dans son corps et dans sa psyché, et de la clinique du féminin, du devenir ou du rester femme. Dans cette perspective, comment appréhender le contenu latent de la demande des femmes qui choisissent la césarienne sans indication médicale pour accoucher de leur premier enfant ? La demande maternelle de césarienne est-elle une modalité spécifique du traitement de la problématique sexuelle œdipienne féminine réactivée par l’accouchement ? Cette recherche qualitative, comparative et longitudinale se déroule au sein du service de gynécologie obstétrique de l’Institut hospitalier Franco-Britannique. À partir d’un échantillon composé de 24 femmes, je compare les processus psychiques des parturientes qui demandent une césarienne sans indication médicale, pour accoucher d’un premier enfant, et ceux des parturientes « tout venant ». Je les rencontre au cours d’entretiens semi-directifs de recherche réalisés à trois temps différents : au cours du troisième trimestre de la grossesse, lors de leur séjour à la maternité et à deux mois de post-partum. / In the context of the medicalization of birth and the banalization of caesarian sections,the literature and clinical experience demonstrate the rise of maternal requests for c-section,without medical indication, for the delivery of a first child. The research explores, within apsychoanalytical frame of reference, the singular somatopsychic experience that constituteschildbirth. It approaches the question of the use of the genital passage from the perspective ofinstinctive effraction, with reference to the Freudian theory of trauma articulated with that offemale psychosexual development. Could the recourse to the caesarian delivery be understoodas a specific method for the treatment of sexual excitation — genital and infantile — causedby the representations and the experience of the body during childbirth? Methodology : Aclinical, qualitative, comparative and longitudinal research conducted in three time periods ofpre- and postpartum. The research tools used are clinical semi-directed research interviews,drawings and self-assessment questionnaires. The sample was made up of 22 primiparae, 10having elected a caesarian delivery and 12 from the general patient population. Results :Elective c-section would permit the containment of the instinctive intensity caused by themanifest representations of the corporal experience of vaginal delivery; whereas in the generalpopulation group, the fear of pain would appear to play the role of a latent protective shield.The conflict between the fantasmatic realization of the oedipal desires and the necessarymaintenance of the link to the maternal imago would be replayed during the time of thedelivery for the women of both groups. The refusal of the passive position and, in certaincases, the existence of a fusional link to the preoedipal maternal imago would becharacteristic of the women having elected a caesarian delivery. For most of them, therecourse to a c-section would appear to contribute to liberation from the always prevalentprimary object; the recourse to the c-section serving the function of third party separator.Other research paths, such as the fragility of the corporal shoring as support of narcissismcould translate the emergence, appeared during the course of this research and would need tobe explored through further research.

This thesis is concerned with caching algorithms. We investigate three variations of the caching problem: web caching in the Torng framework, relative competitiveness and caching with request reordering. <br /><br /> In the first variation we define different cost models involving page sizes and page costs. We also present the Torng cost framework introduced by Torng in [29]. Next we analyze the competitive ratio of online deterministic marking algorithms in the BIT cost model combined with the Torng framework. We show that given some specific restrictions on the set of possible request sequences, any marking algorithm is 2-competitive. <br /><br /> The second variation consists in using the relative competitiveness ratio on an access graph as a complexity measure. We use the concept of access graphs introduced by Borodin [11] to define our own concept of relative competitive ratio. We demonstrate results regarding the relative competitiveness of two cache eviction policies in both the basic and the Torng framework combined with the CLASSICAL cost model. <br /><br /> The third variation is caching with request reordering. Two reordering models are defined. We prove some important results about the value of a move and number of orderings, then demonstrate results about the approximation factor and competitive ratio of offline and online reordering schemes, respectively.

In this thesis, we study the broadcast scheduling algorithms in a dynamic environment with set-typed data requests. We sketch the dimensions of broadcasting paradigms and build a family of Wp

In this paper, we present a new routing protocol which using the characteristic of Bluetooth on Bluetooth-based mobile ad hoc networks. After observing the existing ad hoc routing protocol, we found there exist some useless routing packets which was helpless to build the routing path and increasing the load of network. We present a new Bluetooth routing protocol (BRP) which use the limited routing table in master device to reducing the routing table size and routing packets. In the simulation results, we show that BRP can reduce the routing overhead in network and avoid to product useless routing packets.

WiMAX (Worldwide Interoperability for Microwave Access) provides wide transmission range and broadband network services. However, in IEEE 802.16 standard, there is no specific definition for SS (Subscriber Station) to select an optimal route in a mesh-based WiMAX network. In this thesis, we propose an Optimal Route Selection Scheme (ORSS) for SS to select a route to its BS (Base Station). ORSS basically considers three influential factors, the bandwidth SS to be assigned, the number of interference nodes around SS, and the hop counts to BS. We also investigate QoS (Quality of Service) issue in a mesh-based WiMAX network; an SS transferring the rtPS traffic type will share bandwidth with the neighboring SS of the same level that transmit the same traffic type. To ensure the selected route that can meet the bandwidth requirements of rtPS and the delay constraints, we estimate the average transmission delay from SS to BS. For the purpose of evaluation, we establish a mathematical model to analyze the proposed ORSS and discuss the impact of varying network parameters on the successful rate of route selection. Through the Matlab simulation, we validate our mathematical model. The simulation results demonstrate that our ORSS, in comparison to a previous work, is more effective in ensuring the delay constraints when selecting a route to transfer rtPS traffic.