In this thesis, a modified routing protocol, MAODV (Modified Ad Hoc On-Demand Distance Vector), is proposed for wireless Ad Hoc networks. MAODV uses ACK paths for rerouting data traffic whenever there is a route failure. We create new flags in the routing information of AODV to timely notify TCP layer the network status. After a route failure, the source node monitors ACK packets from the destination node. Every ACK packet when it is received from the destination node, its carried information is used to update the routing tables. Thus, without any interruption, TCP can take the reverse route of the ACK forwarding paths to continue to transmit the rest of data packets. In our proposed scheme, without decreasing the size of TCP congestion window (CWND), a lost packet can be immediately retransmitted as soon as the first duplicate ACK is received. We use NS-2 to simulate the proposed MAODV. From our simulation results, we have shown that when the position of route failures is near the source node, it may take more time to find new data paths. Hence, MAODV has the advantages by taking the reverse ACK paths to transmit data packets before new routing paths are found. Finally, we have demonstrated that MAODV performs better than TCP-BuS (BUffering capability and Sequence information) and the original TCP, when there are many hops between the source node and the destination node. On the other hand, when the position of route failures is near the destination node, the advantages of MAODV become not so significant because there exists some local repair mechanisms to be applied.

An ad-hoc network operates without a central entity or infrastructure, and is composed of highly mobile hosts. In ad-hoc network, routing protocols are with host mobility and bandwidth constraints. There have been many recent proposals of routing protocols for ad-hoc networks. A recent trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required. AODV(Ad-hoc On-demand Distance Vector routing) evaluates routes only on an as-needed basis and routes are maintained only as long as they are necessary. Because the network topology changes frequently in ad-hoc networks, some on-demand protocols with multi-paths or backup routes have been proposed. Sung-Ju Lee and Mario Gerla proposed an AODV-BR scheme to improve existing on-demand routing protocols by creating a mesh and providing multiple alternate routes . The algorithm establishes the mesh and multi-path using the RREP (Route Reply) of AODV, which does not transmit any extra control message. In this paper, we propose two schemes : AODV-ABR(Adaptive Backup Route) and AODV-ABL (Adaptive Backup Route and Local repair) to increase the adaptation of routing protocol to topology changes by modifying AODV-BR. In AODV-ABR, the alternative route can be creating by overhearing not only RREP packets but also data packets. AODV-ABL combines the benefits of AODV-ABR and Local Repair. Finally, we evaluate the performance improvement by simulation.

With recent growth in mobile components and advances in wireless communication technology, mobile computing is an increasingly important area of research. Enabling mobility in IP networks becomes more and more significant. Mobile IP is the only current means for offering seamless roaming to mobile computers in the Internet. It has recently progressed along the ladder to standardization within the Internet Engineering Task Force (IETF). However, Mobile IP suffers from so-called triangular-routing problem and packet loss due to handoff. In this paper, we propose a new architecture to solve these two problems noted above. We assume that network routers such as Home Agent¡BForeign Agent¡BGeneral Router can equip our Pre-Accessing Engine (Mobile IP Engine) to access IP packets before IP routing Engine. With our Mobile IP table established in Mobile IP Engine, we can set up a transmission path for each correspondent node (CN) to transmit data to mobile node (MN). Therefore, we not only solve triangular-routing problem by direct transmission path, but also decrease handoff latency from path updating function. Furthermore, we use retransmission and flush schemes to avoid packet loss and out-of-order problems. Finally, we use simulation to prove our architecture is useful.

Mobile ad hoc network is an architecture which do not exist any infrastructure or centralized administration. There are many routing protocols have been proposed so far, such as AODV, DSR and CGSR. These protocols were classified as reactive in which routes are established only when required. Due to the movement of mobile nodes, network topology changes frequently, and the routing path could be broken easily. This phenomenon will cause higher routing overhead and delivery latency. In conventional routing protocols, the source-destination pair only establishes a single path for data transmission. These routing scheme, however, suffer from the drawback of node movement. When route broken, the source node must reconstruct another new path. This paper presents an adaptive routing protocol named Adaptive Route Selection Scheme of Multiple Paths for Mobile Ad Hoc Network (ARSMA). The aim of the work is to improve the delivery ratio. In the route request phase, source nodes will discovery two routes to the destination node, one for primary path, and the other for the backup path. During the discovery procedure, each node will estimate the link expire time through the movement speed and direction of the precursor node. When a link breakage is about to occur, source node will try to switch the transmission to the backup route.The simulation result shows that ARSMA is able to achieve a remarkable improvement in delivery ratio and end-to-end dealy.

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.

<p>I grundskolan skiljer det sig mycket från elev till elev när det gäller konsten att behärska läsning. Då läsning är något som tränas genom övning är det oftast de som tycker det är svårt som håller sig borta från läsandet. DAISY är ett format som erbjuder läsare att, samtidigt som de läser en text, få den uppläst. Genom att presentera text både visuellt och auditivt kan fokus tas bort från själva ordavkodningen, vilket är det som de flesta i läs- och skrivsvårigheter har problem med. I detta arbete undersöktes läshastighet, läsförståelse och läseffektivitet på 18 åttondeklassare, varav sju uppvisade olika grader av läs- och skrivsvårigheter. Resultaten mellan när de läste en text med DAISY och när de läste en text utan DAISY jämfördes. Resultatet visade att deltagarna läste långsammare med DAISY än utan. De i läs- och skrivsvårigheter hade dock både en större läsförståelse och läseffektivitet när de använde DAISY.</p>

Texte remanié de: Th. doct.--Hist.--Paris--EPHE, 1999. / Bibliogr. p. 337-379. Index.

Reproduction de : Thèse doctorat : Histoire contemporaine : Poitiers : 2009. / Titre provenant de l'écran titre. Bibliogr. Réf. bibliogr.

In many countries across the world, fossil fuels, especially petroleum, are the largest energy source for powering the socio-economic system and the transportation sector dominates the consumption of petroleum in these societies. As the petroleum price continuously climbs and the threat of global climate changes becomes more evident, the world is now facing critical challenges in reducing petroleum consumption and exploiting alternative energy sources. A massive adoption of plug-in electric vehicles (PEVs), especially battery electric vehicles (BEVs), offers a very promising approach to change the current energy consumption structure and diminish greenhouse gas emissions and other pollutants. Understanding how individual electric vehicle drivers behave subject to the technological restrictions and infrastructure availability and estimating the resulting aggregate supply-demand effects on urban transportation systems is not only critical to transportation infrastructure development, but also has determinant implications in environment and energy policy enactment. Driving PEVs inevitably changes individual’s travel and activity behaviors and calls for fundamental changes to the existing transportation network and travel demand modeling paradigms to accommodate changing cost structures, technological restrictions, and supply infrastructures. A prominent phenomenon is that all PEV drivers face a distance constraint on their driving range, given the unsatisfactory battery-charging efficiency and scarce battery-charging infrastructures in a long period of the foreseeable future. Incorporating this distance constraint and the resulting behavioral changes into transportation network equilibrium and travel demand models (static and/or dynamic) raises a series of important research questions. This dissertation focuses on analyzing the impact of a massive adoption of BEVs on urban transportation network flows. BEVs are entirely dependent on electricity and cannot go further once the battery is depleted. As a modeling requirement in its simplest form, a distance constraint should be imposed when analyzing and modeling individual behaviors and network congestions. With adding this simple constraint, this research work conceptualizes, formulates and solves mathematical programming models for a set of new BEV-based network routing and equilibrium problems. It is anticipated that the developed models and methods can be extensively used in a systematic way to analyze and evaluate a variety of system planning and policy scenarios in decision-making circumstances of BEV-related technology adoption and infrastructure development. / text

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