Network performance maps can be used as a tool to predict network conditions at a given location, based on previous measurements at that location. By using measurement data from other users in similar locations, these predictions can be significantly improved. This thesis looks into the accuracy of predictions when using different approaches to distribute this data between users, we compare the accuracy of predictions achieved by using a central server containing all known measurements to the accuracy achieved when using a crowd-based approach with opportunistic exchanges between users. Using data-driven simulations, this thesis also compares and evaluates the impact of using different exchange policies. Based on these simulations we conclude which of the exchange policies provides the most accurate predictions.

CluSys is a simulation platform that is developed by LuK GmbH & Co. KG to support product development engineers. It integrates different simulation calculation kernels and provides a collaborative environment for tool-independent chain simulation processes. The data between simulation modules in chain simulations is exchanged by defining intercommunications between individual parameters manually. This thesis provides a concept to automate the data exchange process between the parameters of different simulation models based on their physical meaning. Different approaches implemented in contemporary simulation environments are discussed, analyzed and a customized solution compatible with CluSys based on abstract interface approach is developed. This concept is implemented using an SQL database creating a parameter dictionary and an automatic intercommunication interface that uses the dictionary to recognize the parameters and define data exchange processes between them automatically. The implemented solution makes the data exchange between parameters of different simulation models independent of their labels, module names or units.

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No description available.

Unmanned aerial vehicle (UAV) networks, a flying platform, are a promising wireless communications infrastructure with wide-ranging applications in both commercial and military domain. Owing to the appealing characteristics, such as high mobility, high feasibility, and low cost, UAV networks can be applied in various scenarios, such as emergency communications, cellular networks, device-to-device (D2D) networks, and sensor networks, regardless of infrastructure and spatial constraints. To handle complicated missions, provide wireless coverage for a large range, and have a long lifetime, a UAV network may consist of a large amount of UAVs, working cooperatively as a swarm, also referred to as swarm UAV networks. Although high mobility and numerous UAVs offer high flexibility, high scalability, and performance enhancement for swarm UAV networks, they also incur some technical challenges. One of the major challenges is the routing protocol design. With high mobility, a dynamic network topology may be encountered. As a result, traditional routing protocols based on routing path discovery are not applicable in swarm UAV networks, as the discovered routing path may be outdated especially when the amount of UAVs is large causing considerable routing path discovery delay. Multicast is an essential and key technology in the scenarios, where swarm UAV networks are employed as aerial small base station (BSs), like relay or micro BS. Swarm UAV networks consisting of a large amount of UAVs will encounter severe multicast delay with existing multicast methods using acknowledgement (ACK) feedback and retransmissions. This issue will be deteriorated when a swarm UAV network is deployed far away from BSs, causing high packet loss. Data exchange is another major technical challenge in swarm UAV networks, where UAVs exchange data packets with each other, such as requesting and retrieving lost packets. Due to numerous UAVs, data exchange between UAVs can cause message and signaling storm, resulting in a long data exchange delay and severe ovehead. In this dissertation, I focus on developing novel routing protocols, multicast schemes, and data exchange schemes, enabling efficient, robust, and high-performance routing, multicast, and data exchange in swarm UAV networks. To be specific, two novel flooding-based routing protocols are designed in this dissertation, where random network coding (RNC) is utilized to improve the efficiency of the flooding-based routing in swarm UAV networks without relying on network topology information and routing path discovery. Using the property of RNC that as long as sufficient different versions of encoded packets/generations are accumulated, original packets could be decoded, RNC is naturally able to accelerate the routing process. This is because the use of RNC can reduce the number of encoded packets that are required to be delivered in some hop. In a hop, the receiver UAV may have already overheard some generations in previous hops, so that it only needs to receive fewer generations from the transmitter UAV in the current hop. To further expedite the flooding-based routing, the second flooding-based routing protocol is designed, where each forwarding UAV creates a new version of generation by linearly combining received generations rather than by decode original packets. Despite the flooding-based routing significantly hastened by RNC, the inherent drawback of the flooding-based routing is still unsolved, namely numerous hops. Aiming at reducing the amount of hops, a novel enhanced flooding-based routing protocol leveraging clustering is designed, where the whole UAV network will be partitioned into multiple clusters and in each cluster only one UAV will be selected as the representative of this cluster, participating in the flooding-based routing process. By this way, the number of hops is restricted by the number of representatives, since packets are only flooded between limited representatives rather than numerous UAVs. To address the multicast issue in swarm UAV networks, a novel multicast scheme is proposed based on clustering, where a UAV experiencing packet loss will retrieve the lost packets by requesting other UAVs in the same cluster without depending on retransmissions of BSs. In this way, the lost packet retrieval is carried out through short-distance data exchange between UAVs with reliable transmissions and a short delay. Tractable stochastic geometry tools are used to model swarm UAV networks with a dynamic network topology, based on which comprehensive analytical performance analysis is given. To enable efficient data exchange between UAVs in swarm UAV networks, a data exchange scheme is proposed utilizing unsupervised learning. With the proposed scheme, all UAVs are assigned to multiple clusters and a UAV can only carry out data exchange within its cluster. By this way, UAVs in different clusters perform data exchange in a parallel fashion to expedite data exchange. The agglomerative hierarchical clustering, a type of unsupervised learning, is used to conduct clustering in order to guarantee that UAVs in the same cluster are able to supply and supplement each other's lost packets. Additionally, a data exchange mechanism, including a novel random backoff procedure, is designed, where the priorities of UAVs in data exchange determined by the number of their lost packets or requested packets that they can provide. As a result, each request-reply process would be taken fully advantage, maximally supplying lost packets not only to the UAV sending request, but also to other UAVs in the same cluster. For all the developed technologies in this dissertation, their technical details and the corresponding system procedures are designed based on low-complexity and well-developed technologies, such as the carrier sense multiple access/collision avoidance (CSMA/CA), for practicability in practice and without loss of generality. Moreover, extensive simulation studies are conducted to demonstrate the effectiveness and superiority of the proposed and developed technologies. Additionally, system design insights are also explored and revealed through simulations. / Doctor of Philosophy / Compared to fixed infrastructures in wireless communications, unmanned aerial vehicle (UAV) networks possess some significant advantages, such as low cost, high mobility, and high feasibility, making UAV networks have a wide range of applications in both military and commercial fields. However, some characteristics of UAV networks, including dynamic network topology and numerous UAVs, may become technical barriers for wireless communications. One of the major challenges is the routing protocol design. Routing is the process of selecting a routing path, enabling data delivered from a node (source) to another desired node (destination). Traditionally, routing is performed based on routing path discovery, where control packets are broadcasted and the path, on which a control packet first reaches the destination, will be selected as routing path. However, in UAV networks, routing path discovery may experience a long delay, as control packets go through many UAVs. Besides, the discovered routing path may be outdated, as the topology of UAV networks change over time. Another key technology in wireless communications that may not work well in UAV networks is multicast, where a transmitter, like a base station (BS), broadcasts data to UAVs and all UAVs are required to receive this data. With numerous UAVs, multicast delay may be severe, since the transmitter will keep retransmitting a data packet to UAVs until all UAVs successfully receive the packet. This issue will be deteriorated when a UAV network is deployed far away from BSs, causing high packet loss. Data exchange between UAVs is a fundamental and important system procedure in UAV networks. A large amount of UAV in a UAV network will cause serious data exchange delay, as many UAVs have to compete for limited wireless resources to request or send data. In this dissertation, I focus on developing novel technologies and schemes for swarm UAV networks, where a large amount of UAVs exist to make UAV networks powerful and handle complicated missions, enable efficient, robust, and high-performance routing, multicast, and data exchange system procedures. To be specific, two novel flooding-based routing protocols are designed, where random network coding (RNC) is utilized to improve the efficiency of flooding-based routing without relying on any network topology information or routing path discovery. The use of RNC could naturally expedite flooding-based routing process. With RNC, a receiver can decode original packets as long as it accumulates sufficient encoded packets, which may be sent by different transmitters in different hops. As a result, in some hops, fewer generations may be required to be transmitted, as receivers have already received and accumulated some encoded in previous hops. To further improve the efficiency of flooding-based routing, another routing protocol using RNC is designed, where UAVs create new encoded packets by linearly combining received encoded packets rather than linearly combing original packets. Apparently, this method would be more efficient. UAVs do not need to collect sufficient encoded packets and decode original packets, while only linearly combining all received encoded packets. Although RNC could effectively improve the efficiency of flooding-based routing, the inherent drawback is still unsolved, which is a large amount of hops caused by numerous UAVs. Thus, an enhanced flooding-based routing protocol using clustering is designed, where the whole UAV network will be partitioned into multiple clusters. In each cluster only one UAV will be selected as the representative of this cluster, participating in the flooding-based routing process. By this way, the number of hops could be greatly reduced, as packets are only flooded between limited representatives rather than numerous UAVs. To address the multicast issue in swarm UAV networks, a novel multicast scheme is proposed, where a UAV experiencing packet loss will retrieve its lost packets by requesting other UAVs in the same cluster without depending on retransmissions of BSs. In this way, the lost packet retrieval is carried out through short-distance data exchange between UAVs with reliable transmissions and a short delay. Then, the optimal number of clusters and the performance of the proposed multicast scheme are investigated by tractable stochastic geometry tools. If all UAVs closely stay together in a swarm UAV network, long data exchange delay would be significant technical issue, since UAVs will cause considerable interference to each other and all UAVs will compete for spectrum access. To cope with that, a data exchange scheme is proposed leveraging unsupervised learning. To avoid interference between UAVs and a long-time waiting for spectrum access, all UAVs are assigned to multiple clusters and different clusters use different frequency bands to carry out data exchange simultaneously. The agglomerative hierarchical clustering, a type of unsupervised learning, is used to conduct clustering, guaranteeing that UAVs in the same cluster are able to supply and supplement each other's lost packets. Additionally, a data exchange mechanism is designed, facilitating that a UAV with more lost packets or more requested packets has a higher priority to carry out data exchange. In this way, each request-reply process would be taken fully advantage, maximally supplying lost packets not only to the UAV sending request, but also to other UAVs in the same cluster. For all the developed technologies in this dissertation, their technical details and the corresponding system procedures are designed based on low-complexity and well-developed technologies, such as the carrier sense multiple access/collision avoidance (CSMA/CA), for practicability in reality and without loss of generality. Moreover, extensive simulation studies are conducted to demonstrate the effectiveness and superiority of the developed technologies. Additionally, system design insights are also explored and revealed through simulations.

During the last decades the road traffic has increased tremendously leading to congestion, safety issues and increased environmental impacts. As a result, many countries are continuously trying to find improvements and new solutions to solve these issues. One way of improving the traffic conditions is by the use of so called intelligent transport systems, where information and communication technologies are being used for traffic management and control. One such system commonly used for traffic management purposes are variable speed limit systems. These systems are making use of signs to show speed limits adjusted to the prevailing road or traffic conditions. The rapid development in telecommunication technologies has enabled communication between vehicles, and between vehicles and the infrastructure, so called cooperative systems. This opens up for  the possibility to further improve the performance of a standard variable speed limit system by adding cooperative system features. The overall aim of this thesis is to investigate the potential benefits of incorporating infrastructure to vehicle communication and autonomous control to an existing variable speed limit system. We show how such a cooperative variable speed limit system can be modeled and evaluated by the use of microscopic traffic simulation. Results from the evaluation indicate increased flow harmonization in terms of narrowing of the acceleration rate distribution and reduced exhaust emissions. Further, we compare four control algorithms for deciding on speed limits in variable speed limit systems. Differences in the resulting traffic performance between the control algorithms are quantified by the use of microscopic traffic simulation. It is concluded that the dened objective for the algorithms have a decisive influence on the effects of the variable speed limit system. The results from this thesis are useful for further development of variable speed limit systems, both with respect to incorporating cooperative features and by improving the speed setting control algorithms.

Data exchange between different information systems is a complex issue. Each system, designed for a specific purpose, is defined using a vocabulary of the specific business. While Web services allow interoperations and data communications between multiple systems, the clients of the services must understand the vocabulary of the targeting data resources to select services or to construct queries. In this thesis we explore an ontology-based approach to facilitate clients’ queries in the vocabulary of the clients’ own domain, and to automate the query processing. A governmental inter-department data query process has been used to illustrate the capability of the semantic approach.

Η παρούσα εργασία εξετάζει το πρόβλημα του συγχρονισμού των παραγωγικών διαδικασιών και το πρόβλημα της ανταλλαγής πληροφοριών μεταξύ οργανισμών και επιχειρήσεων κατά τη διάρκεια της συνεργασίας τους για την πραγματοποίηση της επιχειρηματικής διαδικασίας παραγωγής ενός προϊόντος και της παροχής υπηρεσιών. Παρουσιάζεται ένα ολοκληρωμένο πλαίσιο βασισμένο στην σύγχρονη πληροφορική τεχνολογία για το συγχρονισμό των παραγωγικών διαδικασιών που εκτελούνται από τους παραγωγικούς πόρους των συνεργαζόμενων οργανισμών και επιχειρήσεων καθώς και για την ολοκλήρωση των πληροφορικών τους συστημάτων. Ο στόχος του πλαισίου είναι η υποστήριξη της συνεργασίας των οργανισμών και επιχειρήσεων με χρήση πληροφορικής τεχνολογίας καθώς και η διαχείριση της πληροφορίας που ανταλλάσσεται μεταξύ τους για τη διεκπεραίωση των εμπορικών τους συναλλαγών με τον πιο αποδοτικό τρόπο προκειμένου να επιτευχθεί μείωση του συνολικού κόστους λειτουργίας της αλυσίδας των συνεργαζόμενων οργανισμών. Η προτεινόμενη προσέγγιση εφαρμόζεται για την υποστήριξη των εμπορικών δραστηριοτήτων που πραγματοποιούνται μεταξύ οργανισμών και επιχειρήσεων κατά τη διάρκεια της ναυπηγοεπισκευαστικής διαδικασίας. Στη ναυπηγοεπισκευαστική βιομηχανία η εφαρμογή της πληροφορικής τεχνολογίας βρίσκεται στα αρχικά της στάδια. Τα λογισμικά συστήματα τα οποία χρησιμοποιούνται, χαρακτηρίζονται ως "νησίδες αυτοματισμού" διότι το κάθε ένα αντιμετωπίζει τμήμα της όλης διαδικασίας. Ταυτόχρονα είναι δύσκολη η ολοκλήρωση και η επικοινωνία των υπαρχόντων συστημάτων λόγω του διαφορετικού τρόπου αποθήκευσης των δεδομένων και του διαφορετικού επιπέδου αυτοματισμού της κάθε εφαρμογής. Επίσης ο μεγάλος όγκος των δεδομένων που ανταλλάσσεται, δημιουργεί πρόσθετη πολυπλοκότητα λόγω της δυσκολίας μεταφοράς τους και της ανάγκης εισαγωγής τους σε διαφορετικά συστήματα προκειμένου να γίνει η απαραίτητη επεξεργασία τους για τη συνέχιση της επιχειρηματικής διαδικασίας. Επιπλέον στην πραγματοποίηση μιας ναυπηγοεπισκευής λαμβάνουν μέρος εξωτερικοί υπεργολάβοι και προμηθευτές με αποτέλεσμα η διαδικασία συγχρονισμού των εργασιών με τις εργασίες που εκτελούνται από τους παραγωγικούς πόρους του ναυπηγείου να περιπλέκεται. Στο προτεινόμενο πλαίσιο, περιγράφεται η προσέγγιση ολοκλήρωσης λογισμικών συστημάτων με σκοπό την οργανωμένη διαχείριση και δόμηση της πληροφορίας. Συγκεκριμένα η πληροφορία που ανταλλάσσεται μοντελοποιείται με βάση σύγχρονα πρότυπα ανταλλαγής και αναπαράστασης δεδομένων, με στόχο την ανάπτυξη λογισμικού που αναλαμβάνει την ανταλλαγή δεδομένων μεταξύ των συνεργαζόμενων οργανισμών και επιχειρήσεων. Με τη χρήση ενός τέτοιου συστήματος επιτυγχάνεται η ανταλλαγή δεδομένων με ακρίβεια και αξιοπιστία, λόγω της μειωμένης ανθρώπινης παρέμβασης. Επιπλέον με τη χρήση του διαδικτύου επιτυγχάνεται η γρήγορη μεταφορά της πληροφορίας και η ελαχιστοποίηση του χρόνου και του κόστους ανταλλαγής της. Τέλος γίνεται εφαρμογή μεθοδολογίας που προτείνεται στη βιβλιογραφία για τον χρονοπρογραμματισμό των εργασιών που εκτελούνται τόσο από τους παραγωγικούς πόρους του ναυπηγείου όσο και από τους παραγωγικούς πόρους εξωτερικών υπεργολάβων και προμηθευτών. / This work examines the problem of synchronization of production processes and the problem of exchange of information during the collaboration of enterprises, for the realization of the business process within a supply chain. An integrated framework is described, based on the modern information technology for the synchronization of production processes performed by the manufacturing resources of cooperating enterprises as well as for the integration of their information technology (IT) systems. The objective of the framework, is to facilitate the collaboration of enterprises with the adoption of modern standards for data exchange and representation, as well as the management of information that is exchanged among them for the implementation of their commercial and production transactions, with the most efficient way so that to achieve reduction of total cost of operation of the overall supply chain. The proposed approach is applied to support the commercial and production operations in a real life shiprepair environment. In the shiprepair industry the implementation of IT systems, is still immature. The IT systems, which are used, are characterized as "islands of automation" because each one implements only partially the business process. In addition, the integration of existing software systems is difficult, because of the different storage mechanism used by each individual system and the different level of automation of each software application used. Furthermore, the large volume of the exchanged data creates additional complexity, because of the difficulty in the transmission and import of data in heterogeneous software systems used by each shiprepair partner, required to enable the essential data processing for the continuation of the shiprepair business process. Finally, during the shiprepair production process, subcontractors and suppliers are also involved; therefore the synchronization of their work with the work that is executed by the shipyard resources is complicated. The proposed framework, suggests an approach for the integration of IT systems, aiming at the structured management of information. In particular, the information that is exchanged, is modeled based on modern standards for data exchange and representation, aiming at the development of software that implements the exchange of data between the cooperating enterprises. Using such a system, the exchange of data is realized with precision and reliability, due to decreased human intervention in data typing operations. Moreover, with the use of the Internet, fast transmission of information is achieved in parallel to the minimisation of time and cost for data exchange. Finally, this work, describes the implementation of a scheduling methodology suggested in the literature, for planning of the work performed by the manufacturing resources of the cooperating partners in the project type manufacturing system. Finally, the implementation of the suggested approach in a real life shiprepair supply chain is described.

With the growing number of complex requirements for building and facility projects, diverse domain experts iteratively exchange building design and product data during the design, construction, and facility management phases. Such data exchanges, however, frequently involve unintended geometric transformations, inaccurate project requirements, and insufficient syntactic and semantic elements in building model data. To ensure the interoperability of building information models, this dissertation includes an examination of rules categorized from the Precast Concrete Institute model views and a generalization of the rule logic and structures of each rule set. Moreover, rule logic is coded and implemented on modularized validation platforms of a validation tool referred to as the IfcDoc tool, an automated model view documentation and validation application. This dissertation is expected to help domain experts evaluate whether building design data fulfill the data exchange specifications of their domain and the objectives of a proposed project. Furthermore, to identify unreliable and inconsistent IFC mapping procedures of BIM authoring tools, software developers using the proposed approach would implement an automated debugging process in their IFC interfaces according to the specifications of a targeted model view.

Un processus de conception que ce soit d'un produit ou d'un service est composé d'un grand nombre d'activités reliées par des échanges nombreux de données et d'informations. La qualité de ces échanges, appelés collaborations, nécessite d'être capable d'envoyer et de recevoir des informations et données utiles, compréhensibles et univoques pour les différents concepteurs impliqués. La problématique de ces travaux de thèse se focalise donc sur la définition et l'évaluation de la performance des collaborations, et par extension, du processus de conception dans sa totalité. Cette évaluation de la performance exige la définition de plusieurs éléments clefs tels que : les objets à évaluer, les indicateurs de performance et les variables d'actions. Afin de définir l'objet d'évaluation, ces travaux s'appuient sur une étude de la littérature afin de proposer un méta-modèle de la conception collaborative. La mesure de la performance de ces collaborations est quant à elle basée sur le concept d'interopérabilité. Cette mesure estime ainsi l'interopérabilité technique et sémantique des différentes collaborations élémentaires. Ces travaux se concluent par la proposition d'un cadre méthodologique outillé d'évaluation de la performance des collaborations. Par une approche en deux étapes (modélisation puis évaluation), ce cadre facilite l'identification des collaborations peu performantes et de leurs causes. Ce cadre est illustré et partiellement validé à l'aide d'un exemple académique et d'une étude de cas dans le cadre de la conception. / A design process, whether for a product or for a service, is composed of a large number of activities connected by many data and information exchanges. The quality of these exchanges, called collaborations, requires being able to send and receive data and information which are useful, understandable and unambiguous to the different designers involved. The research question is thus focused on the definition and evaluation of the performance of collaborations, and by extension, of the design process in its entirety. This performance evaluation requires the definition of several key elements such as object(s) to be evaluated, the performance indicator(s) and action variable(s).In order to define the object of evaluation, this research relies on a study of the literature resulting in a meta-model of collaborative process. The measurement of the performance of these collaborations is for its part based on the concept of interoperability. The measurement of the performance of the collaborations is for its part based on the concept of interoperability. Furthermore, this measure estimates the technical and conceptual interoperability of the different elementary collaborations. This work is concluded by proposing a tooled methodological framework for collaborations' performance evaluation. Through a two-step approach (modeling and evaluation), this framework facilitates the identification of inefficient collaborations and their causes. This framework is illustrated and partially validated using an academic example and a case study in design domain.