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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An Adaptive Route Optimization Scheme for Mobile IP Networks

Huang, Tien-Chi 02 August 2005 (has links)
In mobile IP, a triangular routing problem usually leads to additional delays and non-seamless handoff, which causes the loss of a large amount of in-fly packets. In this thesis we propose an adaptive route optimization scheme that considers the seamless handoff and mobility rate. The proposed scheme adopts the mobile routing table scheme and includes an efficient cost function. The cost function is a trade-off between network bandwidth utilized by the routing path, signaling messages and processing loads of agents. The primary idea is to adaptively determine when to perform route optimization. The effect of the mobility rate and the cell sojourn time of a mobile node are studied. Both new call and handoff call are considered in the cost calculation. Simulation result shows that the proposed scheme can effectively reduce the total cost composed of link and signaling costs.
2

A Pre-Setup-Path for Fast Handoff in Mobile IP

Lin, Bo-hao 07 September 2004 (has links)
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.
3

Designing optimal demand-responsive transportation feeder systems and comparing performance in heterogeneous environments

Edwards, Derek L. 27 August 2014 (has links)
The goal of this research is to develop a method of objectively comparing and optimizing the performance of demand-responsive transportation systems in heterogeneous environments. Demand-responsive transportation refers to modes of transportation that do not follow fixed routes or schedules, including taxis, paratransit, deviated-route services, ride sharing as well as other modes. Heterogeneous environments are transportation environments in which streets do not follow regular patterns, passenger behavior is difficult to model, and transit schedules and layouts are non-uniform. An example of a typical heterogeneous environment is a modern suburb with non-linear streets, low pedestrian activity, and infrequent or sparse transit service. The motivation for this research is to determine if demand-responsive transportation can be used to improve customer satisfaction and reduce operating costs in suburban and low-density urban areas where fixed-route transportation may be inefficient. This research extends existing comparison and optimization techniques that are designed to work in homogeneous environments. Homogeneous environments refer to transportation systems where the streets follow regular and repeating patterns, passengers are evenly distributed throughout the system, and the transit system is easily modeled. The performance of systems with these characteristics can be approximated with closed-form analytical expressions representing passenger travel times, vehicle distances traveled, and other performance indicators. However, in the low-density urban areas studied in this research, the street patterns and transit schedules are irregular and passenger behavior is difficult to model. In these areas, analytical solutions cannot be found. Instead, this research develops a simulation-based approach to compare and optimize performance in these heterogeneous environments. Using widely-available route-planning tools, open-source transit schedules, and detailed passenger data, it is possible to simulate the behavior of transit vehicles and passengers to such an exacting degree that analytical solutions are not needed. A major technical contribution of this research is the development of a demand-responsive transportation simulator to analyze performance of demand-responsive systems in heterogeneous environments. The simulator combines several open-source tools for route planning with a custom-built demand-responsive vehicle and passenger-itinerary optimizer to simulate individual vehicles and passengers within a large system. With knowledge of the street network, the transit schedule, passenger locations, and trip request times, the simulator will output exact passenger transit times, passenger travel distances, vehicle travel distance, and other performance indicators for a particular transportation setup in a given area. The simulator is used to develop a method of comparing various demand-responsive and fixed-route systems. By predefining a set of performance indicators, such as passenger travel time and operating cost, the simulator can be used to ascertain the performance of a wide array of transportation systems. Comparing the weighted cost of each type of system permits a transportation engineer or planner to determine what type of system will provide the best results in a given area. The simulator is extended to assist in optimization of the demand-responsive transportation system layout. A key problem that needs to be solved when implementing a demand-responsive system is to determine the size, shape, and location of the demand-responsive coverage areas, i.e., the areas in which passengers are eligible for demand-responsive transportation. Using a particle swarm optimization algorithm and the simulation-based comparison technique, the optimal size and shape for a demand-responsive coverage area can be determined. The efficacy of the comparison and optimization techniques is demonstrated within the city of Atlanta, GA. It is shown that for certain areas of the city of Atlanta, demand-responsive transportation is more efficient than the currently implemented fixed-route system. Depending on the objective of the transportation planner, passenger satisfaction as well as operating costs can be improved by implementing a demand-responsive system in certain low-density areas. The techniques introduced in this research, and the simulation tool developed to implement those techniques, provide a repeatable, accurate, and objective method with which to optimize and compare demand-responsive transportation systems in heterogeneous environments.
4

Securing home and correspondent registrations in mobile IPv6 networks

Elshakankiry, Osama January 2011 (has links)
The Mobile IPv6 (MIPv6) protocol enables mobile nodes (MNs) to remain connected to other correspondent nodes (CNs) while roaming the IPv6 Internet. Home and correspondent registrations are essential parts of the MIPv6 protocol, whereby MNs register their care-of addresses (CoAs) with their home agents (HAs) and with their CNs, respectively. Security provision for home and correspondent registrations is a fundamental part of the MIPv6 protocol and has been an open research issue since the early stages of the protocol.This thesis examines state-of-the-art protocols for securing home and correspondent registrations in MIPv6 networks. The strengths and weaknesses of these protocols are discussed. The investigation of these protocols leads to the proposal of an enhanced home registration protocol and a family of correspondent registration protocols. The Enhanced Home Registration (EHR) protocol extends the basic home registration protocol defined in MIPv6 to support the location authentication of MNs to their HAs. The EHR is based on novel ideas of segmenting the IPv6 address space, using a symmetric CGA-based technique for generating CoAs, and applying concurrent CoAs reachability tests. As a result, EHR is able to reduce the likelihood of a malicious MN being successful in luring an HA to flood a third party with useless packets using MIPv6. In addition, EHR enables HAs to help in correspondent registrations by confirming MNs' CoAs to CNs. Simulation studies of EHR have shown that it only introduces a marginal increase in the registration delay, but a significant increase in the signalling overhead as a cost of supporting the location authentication of MNs.The thesis also proposes a family of correspondent registration protocols. These protocols rely on the assistance of home networks to confirm the MNs' ownership of the claimed HoAs and CoAs. The protocols consist of three phases: a creation phase, an update phase and a deletion phase. Informal and formal protocol analyses have confirmed the protocols' correctness and satisfaction of the required security properties. The protocols have been simulated extensively and the results show that they produce lower registration delay and a reduction in the signalling overhead during update and deletion phases. This is at the cost of a varying increase, depending on the protocol variant, in the registration delay and signalling overhead during the creation phase.
5

Internal logistics : Optimizing the flow of goods with milk runs

Millegård, Jessica, Kurzbach, Sven January 2016 (has links)
In today's world the challenge of logistics becomes more and more important for all companies, which consequently contributes to the need of an integrated system of in-house logistics. Goods must flow easily between stations and departments in order to achieve the best utilization of transportation as well as maintaining a good distribution structure to handle these processes in an efficient and effective way to enhance business performance and competitiveness. This report aims to provide research on how to strategically organize, plan and structure the flow of internal logistics within an organization. The research in this study originates from 3 main methods, a theoretical review, a case study and a benchmark. The main idea of the thesis was to contribute with scientific knowledge of improvements that can be achieved within internal logistics targeting companies operating within the service sector. In order to understand the scope of the problem the current state at the case Tropical Islands was analysed and served to identify areas where possible improvements could be achieved. Further on, in combination with the theory and empirical findings the main conclusions of the thesis was the need to strategically organize the flow of internal logistics to improve efficiency and enhance competitiveness. It was made evident that planning is essential in order to successfully implement the milk runs. Other tools could be utilized to further eliminate drawbacks that might occur.
6

Ruttoptimering i en georefererad mikrospatial miljö : ett GIS visualiserat i 3D

Andersson, Martin, Meriä, Markus January 2011 (has links)
Stadsmodeller i 3D är en allt mer bidragande faktor inom GIS och vinster i tid för räddningstjänst vid användandet av 3D-GIS har påvisats. Arbetet presenterat i rapporten behandlar nätverksanalyser i 2D och 3D och har utförts på uppdrag av Gävle kommun.  Uppgiften har utförts med två huvudsakliga mål. Det första målet var att jämföra processtiderna för Dijkstras sökalgoritm mellan nätverk (ett mindre baserat på förvaltningshuset i Gävle och ett överdimensionerat nätverk) i 3D och motsvarande nätverk i 2D, för att sedan avgöra skillnaden. Det andra målet var att utveckla en applikation som tillåter vägledning i 3D för besökare från reception till önskad anställd och få rutten visualiserad i en 3D-modell. Arbetet har i huvudsak genomförts med ESRI ArcGIS Desktop 10 och ArcGIS Engine 10 Developer Kit. Programmeringen har utförts med C# i Visual Studio 2010. Applikationen fungerar dynamiskt genom att den hämtar personalinformation från en tabell med hjälp av SQL-sökningar och rutterna genereras vid varje enskild sökning. Resultaten för analyserna över processtiderna visar att det inte är någon signifikant skillnad mellan 2D- och 3D-nätverken. Den slutsats som kan dras är att processtiden inte är ett skäl att välja bort en 3D-miljö för nätverksanalyser. I framtiden finns stor potential för nätverksanalyser i 3D, framförallt i samverkan med 2D-nätverk. / City models in 3D are a growing factor in GIS and it has been demonstrated that rescue times will be reduced for emergency services with the use of 3D GIS. The work presented in this thesis deals with network analysis in 2D and 3D and has been carried out on behalf of Gävle municipality. The task has been carried out with two main objectives. The first objective was to compare processing times for Dijkstra's search algorithm for networks (one smaller network based on the house of administration (förvaltningshuset) in Gävle and one overdimensioned network) in 3D and the corresponding ones in 2D in order to determine the difference. The second objective was to develop an application which allows 3D guidance for visitors from the reception to the required personnel; the resulting route is then obtained and visualized in a 3D model. The work has mainly been conducted with ESRI ArcGIS Desktop 10 and ArcGIS Engine Developer Kit 10. The programming has been carried out with C# in Visual Studio 2010. The application works by dynamically retrieving employee information from a table by using SQL-queries and individual routes are generated for each search. The analysis results for the process times show that there are no significant differences between the 2D and 3D networks. The conclusion to be drawn is that the process time is not a reason to opt out of a 3D environment for network analysis. In the future there is great potential for network analysis in 3D, especially in conjunction with 2D networks.
7

A Route Optimization Method Using MMA (Middle Mobility Agent) for Mobile IP

Wu, Chen-Chi 11 August 2003 (has links)
Nowadays in mobile and wireless networks environment, Mobile IP is the preferred standard in supporting IP mobility among several standards. However, several problems still need to be solved. One of them is the triangle routing problem. Although drafts have been proposed by the IETF (Internet Engineering Task Force) for solving this problem, the proposed solution can not be achieved unless the draft of the Mobile IP route optimization method becomes a typical standard of the Mobile IP. In this paper, we present an extended routing agent architecture to solve this problem. The Middle Mobility Agent (MMA) in the proposed architecture can intercept datagrams earlier and determine to tunnel the incoming packet or not than the MH¡¦s original home agent. This architecture can solve the triangle routing problem by reducing packet¡¦s routing length. An analytical model and a simulation environment were set up to evaluate and measure the packet¡¦s routing length and delay time of proposed architecture. The evaluation and simulation results demonstrate that the proposed method can reduce the routing length, delay time and solve the triangle routing problem.
8

Implementation of dynamic route optimization - drivers and barriers

Karlsson, Victor, Olsson, Susanna January 2018 (has links)
Svevia is a company working with installation, occupancy and operation of infrastructure. They are currently testing and developing a new system called dynamic route optimization (DynOpt) in cooperation with B and M Systemutveckling. This system is able to contribute to a series of improvements for the company, such as automatization of certain processes, conclude demand on a more local level and create dynamic optimized routes which in the best way handles the determined local demands. Svevia sees great potentials of profits with the system, thereby has an interest of a support for decision-making regarding what may or may not be problematic during a potential implementation of such a system. This report regards a case study of the affects that DynOpt can have on its future users and what impact such effects might have on Svevia, with the goal of determining the drivers and barriers of DynOpt related to soft parameters. The soft parameters in this case study relate to how the changes DynOpt entails may affect the users and why or why not they may desire or be willing to accept these changes. The method used to conclude these drivers and barriers is to firstly gather information from the users by interviews and surveys, which then is analyzed in order to determine what advantages and disadvantages the users see with the system. The second step of the data processing consists of a SWOT-analysis execution. The strategic effects are determined through consultation with insight personnel. Lastly the remaining significant results are converted into drivers and barriers by firstly eliminating the information that may not pan out in any driver or barrier and secondly lumping together result describing similar effects into drivers and barriers. Eleven drivers and six barriers are concluded. Such results are for example the driver that the potential future users’ interest in technology may ease the implementation since DynOpt is a technological implementation. One of the barriers on the other hand is that the total driving distance will be reduced through optimization, which results in less available work for the chauffeurs which worsens their working conditions and can result in resistance to the implementation. This driver and barrier as well as the others in conjunction with a discussion, constitute the final result of the report and describe aspects that may hinder or make it easier to successfully implement DynOpt.
9

Ekonomické vyhodnocení podnikatelského záměru dopravní firmy / Economic assessment of a business plan of a transport company

POPELOVÁ, Vladimíra January 2016 (has links)
The main aim of the Dissertation was to create a method enabling evaluation of a business plan of a firm doing business in the field of freight transport. The Dissertation is based on an actual investment project in which the transport company takes part in two tender procedures. The specific nature of the transport sector complicated the possibility to use classical methods for the evaluation of investment efficiency. Application of the net pre-sent value method to an already implemented investment project confirmed that this method cannot be used to assess the business plan of the transport company. For this reason, it was necessary to draw up a price creation method for both the tender procedures able to en-sure positive profitability of the project with regard to specifics in particular tenders. The subject matter of the tender procedures was the request for proposal concerning vehicle sets of various specifications. The NAL (net advantage to leasing) method was used to decide about the manner of funding of the vehicle sets. For the other tender procedure, a calculation was made to optimize the route in terms of costs, whereby usability of the price creation method was verified in practice.
10

Mobilní aplikace - bezbariérové trasy v rámci centra města / Mobile Application - Barrier-Less Trajectories in City Centre

Podola, Adam January 2017 (has links)
This diploma thesis describes the fundamentals of the Android framework for the future development of mobile applications. The reader will be introduced to existing applications for the support of physically disabled people. It will also describe the design and implementation of a new mobile application, displaying information on selected buildings and giving the possibility of marking obstacles in the public space near the city centre of Brno. Finally, the principle of the chosen procedure of finding potentially barrier-free routes, during which the state of the obstacle database is taken into account, will be explained.

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