One feature that distinguishes a mobile ad hoc network (MANET) from traditional wired networks is that all hosts are allowed to move freely without the need for static access points. This distinct feature, however, presents a great challenge to the design of the routing scheme and the support of multimedia services, since the link quality and the network topology may be fast changing as hosts roam around. This dissertation investigates three major areas in mobile ad hoc networks: (a) Dynamic IP routing in highly mobile environments; (b) Quality-of-Service (QoS) Routing support; and (c) Integration of ad hoc networks with wide area mobile networks. Dynamic routing in MANETs is a multi-objective task that presents stringent requirements. These requirements include: high accuracy, low overhead, robust path maintenance, scalability, in terms of network control overhead, as the network population grows, etc. A new routing approach for routing in ad hoc wireless networks, called Relative Distance Micro-Discovery Ad Hoc Routing (RDMAR) is proposed. RDMAR is an on-demand protocol that reactively discovers and repairs routes within a local region of the network. As demonstrated through simulations, the localisation of routing control messaging serves to minimise communication overhead and overall network congestion. The protocol has been an IETF (Internet Engineering Task Force) candidate since September 1999. To support bandwidth (QoS) sensitive multimedia applications, a new set of slot reservation and distributed channel assignment protocols for mobile ad hoc networks, called MBCA (Minimum Blocking Channel Assignment) and BRCA (Bandwidth Reallocation Channel Assignment), is presented. A fundamental feature of the proposed channel assignment algorithms is that they make use of the congestion states (i.e., available and used bandwidth) of the network. The performance results assert that a basic dynamic channel assignment (DCA) scheme can be significantly improved using the proposed MBCA and BRCA heuristics. Finally, a generic platform for accommodating relaying in the GSM (Global System for Mobile Communications) cellular network is presented. A prototype network layer system model tailored for operation within a GSM-MANET integrated system has been developed for the adaptive routing of calls in the presence of shadowing. The proposed system model is intended to support seamless communication by handing over (rerouting) a suffering call to another mobile terminal, which lies in a more advantageous position and can help as intermediate node of communication between the mobile terminal and base station.

No description available.

The design of the most commonly-used Internet and Local Area Network protocols provide no way of verifying the sender of a packet is who it claims to be. Protocols and applications exist that provide authentication but these are generally for special use cases. A malicious host can easily launch an attack while pretending to be another host to avoid being discovered. At worst, the behavior may implicate a legitimate host causing it and the user to be kicked off the network. A malicious host may further conceal its location by sending the attack packets from one or more remotely-controlled hosts. Current research has provided techniques to support traceback, the process of determining the complete attack path from the victim back to the attack coordinator. Most of this research focuses on IP traceback, from the victim through the Internet to the edge of the network containing the attack packet source, and Stepping-Stone traceback, from source to the host controlling the attack. However, little research has been conducted on the problem of Data-Link Layer Traceback (DLT), the process of tracing frames from the network edge to the attack source, across what is usually a layer-2 network. We propose a scheme called Tagged-fRAme tracebaCK (TRACK) that provides a secure, reliable DLT technique for Ethernet networks. TRACK defines processes for Ethernet switches and a centralized storage and lookup host. As a frame enters a TRACK-enabled network, a tag is added indicating the switch and port on which the frame entered the network. This tag is collected at the network edge for later use in the traceback operation. An authentication method is defined to prevent unauthorized entities from generating or modifying tag data. Simulation results indicate that TRACK provides accurate DLT operation while causing minimal impact on network and application performance. / Master of Science

Communication networks are vulnerable to natural as well as man-made disasters. The geographical layout of the network influences the impact of these disasters. It is therefore, necessary to identify areas that could be most affected by a disaster and redesign those parts of the network so that the impact of a disaster has least effect on them. In this work, we assume that disasters which have a circular impact on the network. The work presents two new algorithms, namely the WHF-PG algorithm and the WHF-NPG algorithm, designed to solve the problem of finding the locations of disasters that would have the maximum disruptive effect on the communication infrastructure in terms of capacity.

In this thesis, we consider a network environment which consists of wired Internet and a wireless broadband network (WiMAX); data from wired or wireless network are all conveyed through WiMAX links to its destination. In order to promise the quality of real-time traffic and allow more transmission opportunity for other traffic types, we propose an Adaptive Bandwidth Allocation (ABA) algorithm for BS to adequately allocate bandwidth. Our ABA algorithm would first reserve required minimum bandwidth for high-priority traffic, such as video streaming. By allocating minimum bandwidth to real-time traffic, the delay time constraint can be satisfied. Other traffic types, such as non-real-time, which have no real-time requirement, may gain extra bandwidth to improve their throughput. For best-effort traffic, the remaining bandwidth can be used to avoid any possible starvation. We build four-dimension Markov chains to evaluate the performance of the proposed ABA algorithm. In the analytical model, we first divide transmission on WiMAX into upload and download phases, and analyze the ABA performance by using Poisson process to generate traffic. At last, by comparing to a previous work, we observe the impacts of different traffic parameters on WiMAX network performance in terms of average delay time, average throughput, and average packet-drop ratio.

A common trend, in general as well as in the field of combat vehicles, is the rapidly increasing demand for data network capacity and even more in transferred data. To handle this increased demand, different countries with their armed forces and equipment manufacturers evaluate methods to increase the data transmission capacity in combat vehicles. The different types of transmitted data are of different criticality and have different security demands. An easy solution to this is to have separated networks for each type of traffic, but that is quite expensive and uses a lot of hardware. This thesis focuses on a different solution, with a shared network for all types of data transmissions. This is done by evaluating different types of data networks and add-on protocols and then testing the networks practically with varying transmission rates. In the thesis, all the practical testing is done with data networks according to the Ethernet standard, which is the standard evaluated with a throughput that is high enough for the use case. Ethernet as a standard is not suitable for critical data traffic and therefore add-on protocols for Ethernet to optimize the system for critical data traffic are tested. With these optimizations made, Ethernet can be considered more suitable for critical traffic, but this depends entirely on the system requirements.

The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases.

Vertical axis wind turbines (VAWTs) have with time been outrivaled by the today common and economically feasible horizontal axis wind turbines (HAWTs). However, VAWTs have several advantages such as the possibility to put the drive train at ground level, lower noise emissions and better scaling behavior which still make them interesting for research. The work within this thesis is made in collaboration between the Department of Construction and Energy Engineering at Halmstad University and the Division for Electricity at Uppsala University. A 200 kW VAWT owned by the latter and situated close to Falkenberg in the southwest of Sweden has been the main subject of the research even if most learnings has been generalized to fit a typical vertical turbine. This particular turbine has a wooden tower which is semi-guy-wired, i.e. the tower is both firmly attached to the ground and supported by guy-wires. This thesis has two main topics both regarding VAWTs: eigenfrequency of the tower and the noise generated from the turbine. The eigenfrequency of a semi-guy-wired tower is studied and an analytical expression describing this is produced and verified by experiments and simulations. The eigenfrequency of the wire itself and how it is affected by wind load are also studied.  The noise characteristics of VAWTs have been investigated, both theoretically and by noise measurement campaigns. Both noise emission and frequency distribution of VAWTs has been studied. The work has resulted in analytical expressions for tower and wire eigenfrequency of a semi-guy-wired tower as well as recommendations for designing future towers for VAWTs. The noise emission of VAWTs has been studied and proven low compared to HAWTs. The noise frequency distribution of the 200 kW VAWT differs significantly from that of a similar size HAWTs with for example lower levels for frequencies below 3000 Hz.

Η παρούσα διπλωματική εργασία αφορά την μοντελοποίηση και προσομοίωση της συμπεριφοράς ενσύρματων τηλεπικοινωνιακών καναλιών. Αρχικά, αναλύθηκε το θεωρητικό υπόβαθρο των ενσύρματων τηλεπικοινωνιακών καναλιών και αναπτύχθηκαν τα βασικά μοντέλα που υλοποιήθηκαν στην διπλωματική εργασία. Στην συνέχεια, περιγράφηκε η πλατφόρμα ανάπτυξης STM32-H107 όπου πραγματοποιήθηκε η προσομοίωση του συστήματος και αναλύθηκαν τα βασικά περιφερειακά του επεξεργαστή που χρησιμοποιήθηκαν. Στις τελευταίες ενότητες, αναλύθηκαν το γραφικό περιβάλλον του χρήστη, το σύστημα που τρέχει στην πλατφόρμα και η επικοινωνία μεταξύ των δύο, ενώ μετρήθηκε η αξιοπιστία του συστήματος μέσα από μετρήσεις και σύγκριση των επιθυμητών τιμών SNR που εισήγαγε ο χρήστης με αυτές που επιτύγχανε το σύστημα. / This master thesis deals with the modeling and the simulation of wired telecommunication channels’ behavior. Firstly, the theoretical background of wired telecommunication channels was explained and their basic models were developed. Also, the development board STM32-H107, which was used for the simulation of the system, was described, and the basic processor’s peripherals were analyzed. In the final chapters, the graphical user interface and the application which run on the board, as well as their communication, were presented. System’s reliability was evaluated through comparing the real SNR with the desired SNR.

Apresentamos um novo Protocolo de Controle de Transporte fim-a-fim, implementado somente do lado do transmissor, chamado TCP HolyWood ou, abreviadamente, TCP-HW. Em um ambiente de rede cabeada simulada, TCP HolyWood supera em vazão media três dos mais importantes protocolos TCPs já elaborados. Estamos falando de TCP Reno, TCP Westwood, e TCP Vegas; e em variação de retardo media ao TCP Reno bem como ao TCP Vegas. Alem disso, de acordo com o índice de Jain, nossa proposta e tão imparcial quanto o padrão, TCP Reno. / We introduce a new end-to-end, sender side Transport Control Protocol called TCP HolyWood or in short TCP-HW. In a simulated wired environment, TCP HolyWood outperforms in average throughput, three of the more important TCP protocols ever made, we are talking about TCP Reno, TCP Westwood, and TCP Vegas; and in average jitter to TCP Reno and TCP Vegas too. In addition, according to Jain’s index, our proposal is as fair as TCP Reno, the Standard.