This research is related to computer networks. In this thesis, three main issues are addressed which affect the performance of any computer network: congestion, efficient resources utilization and link failure. Those issues are related to each other in many situations. Many approaches have been suggested to deal with those issues as well as many solutions were applied. Despite all the improvements of the technology and the proposed solutions, those issues continue to be a burden on the system’s performance. This effect is related to the increase of the Quality of Service (QoS) requirements in modern networks. The basic idea of this research is evolving the intelligence of a conventional computer network when dealing with those issues by adding some features of the Software Defined Networking (SDN). This adoption upgrades the conventional computer network system to be more dynamic and higher self-organizing when dealing with those issues. This idea is applied on a system represented by a computer network that uses the Open Shortest Path First (OSPF) routing protocol. The first improvement deals with the distribution of Internet Protocol (IP) routed flows. The second improvement deals with tunnel establishment that serves Multi-Protocol Label Switching (MPLS) routed flows and the third improvement deals with bandwidth reservation when applying network restoration represented by Fast Re-route (FRR) mechanism to sooth the effect of link failure in OSPF/MPLS routed network. This idea is also applied on another system that uses the Enhanced Interior Gateway Routing Protocol (EIGRP) to improve the performance of its routing algorithm. Adopting the SDN notion is achieved by adding an intelligent controller to the system and creating a dialog of messages between the controller and the conventional routers. This requires upgrading the routers to respond to the new modified system. Our proposed approaches are presented with simulations of different configurations which produce fine results.

In this research work we propose a 3D node deployment strategy by carefully considering the unique characteristics of underwater acoustic communication as well as 3D dynamic nature of UWSN. This strategy targets 3D UWSN and not only improves the routing protocol performance significantly in terms of end to end delay and energy consumption but also provides reliability in data transmission. This strategy has been developed step by step from a single line of vertical communication to an effective 3D node deployment for UWSN. Several simulation experiments were carried out after adding different features to the final design to observe their impact on the overall routing performance. Finally, it is verified that this design strategy improves the routing performance, provides reliability to the network and increases network lifetime. Furthermore, we compared our results to the random node deployment in 3D, which is commonly used for analysing the performance of UWSN routing protocols. The comparison results verified our effective deployment design and showed that it provides almost 150% less end-to-end delay and almost 25% less energy consumption to the random deployment. It also revealed that by increasing the data traffic, our 3D node deployment strategy has no loss of data due to several back-up paths available, which is in contrast to random node deployment, where the packet loss occurs by increasing the data traffic. Improving the routing performance by carefully analysing the impact of 3D node deployment strategy and ensuring full sensing, transmission and back-up coverage in a highly unpredictable underwater environment, is a novel approach. Embedding this strategy with any networking protocol will improve its performance significantly.

Ad hoc networks have gained significant importance and gathered huge momentum within the wireless network research community. We explore the novel idea of applying ad hoc networking for urban search and rescue operations. Several algorithms have been proposed and implemented for routing in ad hoc networks and their performance have been thoroughly analyzed. But none of the prior work deals specifically for search and rescue operations, which entail certain specific criteria such as prevention of node loss, maximizing the area of coverage and constant and instantaneous access to a main controller. In this thesis, we propose a centralized and adaptive algorithm tailored for efficient performance of mobile nodes assisting in search and rescue operations. The proposed algorithm assists in finding and maintaining stable links between the mobile nodes and base station, while optimizing the area of coverage and energy efficiency of the nodes. The algorithm is implemented using ns (network simulator), and its performance is compared with that of a widely used ad hoc routing protocol, Ad hoc On-demand Distance Vector (AODV) routing protocol. We use frequency of link breakages, network throughput and routing overhead as our performance metrics. This algorithm can also be extended to provide support for routing among mobile nodes.

Thesis (Ph.D. (Computer Science)) - Rhodes University, 2008.

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Charles G. Boncelet, Dept. of Computer & Information Sciences. Includes bibliographical references.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 41-42).

Thesis (M.S.)--Mississippi State University. Department of Computer Science and Engineering. / Title from title screen. Includes bibliographical references.

Mobile ad hoc networks create communication links without the aid of any infrastructure, forwarding packets among mobile nodes. The MANET research community has identified several fundamental challenges, among which the most prominent is discovering an optimal route between two nodes. Existing work has proposed a plethora of routing protocols. Since each protocol implements its own philosophy and algorithm to target a specific purpose, routing protocols in MANETs show very different characteristics. Selecting a particular protocol for an application or deployment environment involves evaluating many complex inter-dependent tradeoffs and can be an overwhelming task for an application designer. However, this decision can have a significant impact on the success of a system in terms of performance, cost, and responsiveness. Emerging distributed applications deployed in MANETs inherently experience highly dynamic situations, which necessitate real-time routing protocol selection in response to varying scenarios. Most of the relevant research in this area relies on simulation studies or empirical analysis to select a routing protocol, requiring an infeasible amount of time and resources for the approaches to be used in real-time decision making. In my dissertation work, I designed the Chameleon framework to facilitate real-time routing protocol decisions based on given application and environmental characteristics. My approach develops analytical models for important network layer performance measures capturing various inter-dependent factors that affect routing protocol behavior. I provide an analytical framework that expresses protocol performance metrics in terms of environment-, protocol-, and application-dependent parameters. This effort has resulted in detailed models for two important metrics: end-to-end delay and throughput. I specify detailed models for the parameters embedded in the models with respect to the ability of network deployers, protocol designers, and application developers to reasonably provide the information. Finally, in a systematic manner, I outline the Chameleon software framework to integrate the analytical models with parameters specified by these three groups of stakeholders. / text

Ο ανερχόμενος κλάδος των ασύρματων δικτύων αισθητήρων (Wireless Sensor Networks - WSNs) συνδυάζει δυνατότητα αίσθησης, υπολογισμού και επικοινωνίας σε μια μικρή συσκευή. Ενώ οι δυνατότητες ενός και μόνο κόμβου – αισθητήρα (mote) είναι ελάχιστες, η συνύπαρξη πολλών τέτοιων συσκευών δικτυακά συνδεδεμένων μπορεί να οδηγήσουν σε νέες τεχνολογικές δυνατότητες. Κύριος στόχος αυτών των μικρών συσκευών – κόμβων είναι η δειγματοληψία διάφορων φυσικών μεγεθών, η επεξεργασία αυτών των μεγεθών – μετρήσεων και τέλος, η επικοινωνία του κάθε κόμβου με άλλους με στόχο την μετάδοση αυτών των μετρήσεων – πληροφορίας ασφαλώς και αξιόπιστα. Τα κύρια χαρακτηριστικά αυτών των κόμβων όπως, μικρό μέγεθος, χαμηλό κόστος, αυτονομία και δυνατότητα επικοινωνίας είναι που τα κάνουν τόσο ευέλικτα προσδίδοντας έτσι τη δυνατότητα για ανάπτυξη και υλοποίηση χιλιάδων εφαρμογών. Τα ασύρματα δίκτυα αισθητήρων μπορούν να συμβάλουν σε κρίσιμες εφαρμογές που δεν περιορίζονται αποκλειστικά στον ερευνητικό και επιστημονικό χώρο αλλά επεκτείνονται και στον χώρο της υγείας και της ασφάλειας, όπως παρακολούθηση και επίβλεψη ασθενών, πρόβλεψη και αντιμετώπιση φυσικών καταστροφών, οικιακές εφαρμογές, και στοχεύουν στην βελτίωση της ποιότητας ζωής του ατόμου και της κοινωνίας ως σύνολο. Στο πλαίσιο της παρούσας διπλωματικής εργασίας έγινε προσπάθεια προσέγγισης μιας ανεξερεύνητης έως τώρα σε βάθος εφαρμογής Ασυρμάτων Δικτύων Αισθητήρων, των λεγόμενων «έξυπνων» πόλεων, ως προς τις επικοινωνιακές απαιτήσεις και τους περιορισμούς που θέτει και μια προσπάθεια καταγραφής και αξιολόγησης της απόδοσης και της συμπεριφοράς WSN τεχνολογιών υλικού και επικοινωνιακών τεχνικών σε σχέση με τις απαιτήσεις και τους περιορισμούς αυτούς. Παρουσιάζονται πειραματικά δεδομένα από μετρήσεις που διεξήχθησαν σε εξωτερικό περιβάλλον και εξάγονται χρήσιμα συμπεράσματα σχετικά με μελλοντικές κατευθύνσεις. / The increasingly interesting research field of Wireless Sensor Networks combines the possibility of sensing, computing and networking in a small device. While the capabilities of a single sensor node are limited, the combination of multiple such devices communicating over a network may lead to new technological possibilities and challenges. The main goal of these device nodes is the sampling of several physical values, their processing and the communication of the results to other nodes in a safe and reliable way. The main characteristics of wireless sensor nodes such as the small size, the low cost, autonomy and communication capacity render them flexible and suitable for the development of thousands of applications. Wireless sensor networks are most popular for critical applications that go beyond the research and scientific domain expanding to health, environment and security application classes, like surveillance, patient monitoring, natural disaster prediction and home applications, targeted to improve the quality of life of a single person and of society in general. In the context of this master thesis, the state of the art of a WSN application has been investigated, namely smart cities application field, with respect to the imposed networking requirements and communicational restrictions as well as the analysis and evaluation of the behavioral performance of WSN hardware and communication technologies as far as these requirements and limits are concerned. Finally, experimental results are presented based on measurements conducted outdoors and useful conclusions are extracted forming a future roadmap.

Reducing the energy consumption of available resources is still a problem to be solved in Wireless Sensor Networks (WSNs). Many types of existing routing protocols are developed to save power consumption. In these protocols, cluster-based routing protocols are found to be more energy efficient. A cluster head is selected to aggregate the data received from root nodes and forwards these data to the base station in cluster-based routing. The selection of cluster heads should be efficient to save energy. In our proposed protocol, we use static clustering for the efficient selection of cluster heads. The proposed routing protocol works efficiently in large as well as small areas. For an optimal number of cluster head selection we divide a large sensor field into rectangular clusters. Then these rectangular clusters are further grouped into zones for efficient communication between cluster heads and a base station. We perform MATLAB simulations to observe the network stability, throughput, energy consumption, network lifetime and the number of cluster heads. Our proposed routing protocol outperforms in large areas in comparison with the LEACH, MH-LEACH, and SEP routing protocols.