A bidirectional two-hop relay network with decode-and-forward strategy is implemented using GNU Radio (software) and several USRPs (hardware) on Ubuntu (operating system). The relay communication system is comprised of three nodes; Base Station A, Base Station B, and Relay Station (the intermediate node). During the first time slot, Base Station A and Base Station B will each transmit data, e.g., a JPEG file, to Relay Station using DBPSK modulation and FDMA. For the final time slot, Relay Station will perform a bitwise XOR of the data, and transmit the XORed data to Base Station A and Base Station B, where the received data is decoded by performing another XOR operation with the original data.

Using communication signals for radar applications has been a major area of research in radar engineering. In the recent years, due to the widely available wireless signals, a new area of research called commensal radars has emerged. Commensal radars use available wireless Radio Frequency (RF) signals to detect and track targets of interest. This is achieved by placing two antennas, one towards the transmitting base station and the other towards the surveillance area. The signal received by these two antennas are correlated to determine the location and velocity of the target. When a signal passes through a channel, it reflects off the obstacles within its path. These reflections usually degrade quality of the signal and cause interference to the telecommunication systems. To mitigate the effects of the channel on a signal these systems transmit a known bit sequence within each frame. Our goal, with this thesis, is to design and implement a working prototype of a novel architecture for the commensal radar system, which uses these known bit sequences to extract the channel information and determine events of interest. The major novelties of the system are as follows. Firstly, this system will be built upon existing communication systems using Software Defined Radio (SDR) technology. Secondly, this design eliminates the need for a reference antenna, which reduces the cost of the system and creates an opportunity to make the system portable. We name this system Communication-Sensing (CommSense). Since, our plan is to use Global System for Mobile Communication (GSM) as the parent system for the prototype development, we decide to update the name to GSM based Communication-Sensing (GSM-CommSense) system. This thesis begins with theoretical analysis of the feasibility of the GSM-CommSense system. First of all, we perform a link budget analysis to determine the power requirements for the system. Then we calculate the ambiguity function and Cram´er-Rao Lower Bound (CRLB) for a two-path received signal model. With encouraging theoretical results, we design a prototype of the system that can capture real GSM base station broadcast signals. After the design of the GSMCommSense system, we capture channel data from multiple locations with varying environmental conditions. The aim for this set of experiment is to be able to distinguish between different environmental conditions. Then, we performed statistical analysis on the data by means of Probability Density Function (PDF) fitting, a goodness-of-fit test called chi-square test and a clustering algorithm called Principal Components Analysis (PCA). We have presented the results from each analysis and discussed them in detail. Upon, receiving positive results in each step we have decided to move towards using learning algorithms to categorise the data captured by the system. We have compared two widely accepted supervised learning algorithms, called Support Vector Machines (SVM) and Multi-Layer Perceptron (MLP). The results showed that with the current hardware capabilities of the system and the amount of data available per GSM frame, the performance of SVM is better than MLP. Thus, we have used SVM to classify two events of detection and classification across a wall. We have presented our findings and discussed the results in detail. We conclude our current work and provide scope for future work in development and analysis of the GSM-CommSense system.

To achieve greater performance in computing networks, a setup of critical computing aspects that ensures efficient network operation, needs to be implemented. One of these computing aspects is, Quality of Service (QoS). Its main functionality is to manage traffic queues by means of prioritizing sensitive network traffic. QoS capable networking allows efficient control of traffic especially for network critical data. However, to achieve this in Wireless Sensor Networks (WSN) is a serious challenge, since these technologies have a lot of computing limitations. It is even difficult to manage networking resources with ease in these types of technologies, due to their communication, processing and memory limitations. Even though this is the case with WSNs, they have been largely used in monitoring/detection systems, and by this proving their application importance. Realizing efficient network control requires intelligent methods of network management, especially for sensitive network data. Different network types implement diverse methods to control and administer network traffic as well as effectively manage network resources. As with WSNs, communication traffic and network resource control are mostly performed depending on independently employed mechanisms to deal with networking events occurring on different levels. It is therefore challenging to realize efficient network performance with guaranteed QoS in WSNs, given their computing limitations. Software defined networking (SDN) is advocated as a potential paradigm to improve and evolve WSNs in terms of capacity and application. A means to apply SDN strategies to these compute-limited WSNs, formulates software defined wireless sensor networks (SDWSN). In this work, a resource-aware OpenFlow-based Active Network Management (OF-ANM) QoS scheme that uses SDN strategies is proposed and implemented to apply QoS requirements for managing traffic congestion in WSNs. This scheme uses SDN programmability strategies to apply network QoS requirements and perform traffic load balancing to ensure congestion control in SDWSN. Our experimental results show that the developed scheme is able to provide congestion avoidance within the network. It also allows opportunities to implement flexible QoS requirements based on the system’s traffic state. Moreover, a QoS Path Selection and Resource-associating (Q-PSR) scheme for adaptive load balancing and intelligent resource control for optimal network performance is proposed and implemented. Our experimental results indicate better performance in terms of computation with load balancing and efficient resource alignment for different networking tasks when compared with other competing schemes. / Thesis (PhD)--University of Pretoria, 2019. / National Research Foundation / University of Pretoria / Electrical, Electronic and Computer Engineering / PhD / Unrestricted

No description available.

This Diploma thesis deals with virtualization of data networks, but mainly with concept of software-defined networking. Architecture, security risks and differences besides traditional networks are described within SDN framework. Description includes protocol OpenFlow, which is integral part of SDN concept. Brief summary mentions also NFV concept. The goal of this thesis is to determine available solutions, invent laboratory task and compile laboratory manual. Tables with currently available controllers and commutators for SDN were created and pattern of laboratoral task was realized within Mininet emulator and OpenDaylight controller. Laboratoral task itself is designed with aim to apprize students of subject of Network architecture with SDN concept and its real implementation.

This thesis deals with car remote keyless systems, analysis of these systems and most common attacks on these systems. It also deals with design and realisation of secure car remote keyless system, which should be resistant to said attacks, and with design and realisation of attack against existing car remote keyless system.

Nowadays, catalysis lies at the heart of economy growth mainly in the petroleum industry. Catalysis can offer real and potential solutions to the current challenges for a long-term sustainable energy, green chemistry, and environmental protection. In this context, one of the most important and future prosperity promising catalytic applications in the petrochemical field is hydrocarbons metathesis; it consists on the conversion of both renewable and non-petroleum fossil carbon sources to transportation fuels. Olefin metathesis has become one of the standard methodologies for constructing C-C bonds in many organic transformation reactions. This owed to the numerous types of metathesis reactions that have been developed, for example, enyne, ring-opening and closing, self and cross metathesis, etc. But the one step conversion of olefin to alkanes has not been studied much. Recently, only one such a work has been published for the hydro-metathesis of propylene by tantalum hydride supported on KCC-1 in dynamic reactor. With this knowledge, we thought to study the hydro-metathesis using liquid olefin (1-decene). Another aspect of using 1-decene comes from our previous experience on metathesis of n-decane where the first step is the conversion of decane to 1-decene and subsequently to different chain length alkanes with W-alkyl/alkylidene catalyst. In this way, it would be easy for us to use different catalysts and compare them with parent catalyst concerning TON. We found 100% conversion with TON of 1010 using supported WMe6 onto SiO2-700 [(≡Si-O-)WMe5] against the previous results for n-decane showing 20% conversion and TON of 153. In this work, we disclose the hydro-metathesis reaction of 1-decene using well-defined silica supported W(VI), Mo(VI) and Ta(V) alkyl catalysts in batch reactor condition. This work is divided into three major sections; first chapter contains an introduction to the field of catalysis and surface organometallic chemistry. In second chapter, we describe all the experimental procedures of the catalysts. The third chapter is devoted to the characterization and interpretation followed by catalytic reactions. Finally, a brief conclusion of the present study is given.

The aim of this thesis is to develop a load balancing tool for OpenFlow networks. Software-defined networking (SDN) principles are introduced (OpenFlow protocol used as an example) and compared to the legacy routing and switching technology. Openflow is the first protocol/API enabling communication between the control and infrastructure planes of the software-defined networking model. Key features of the protocol are described and several OpenFlow controllers are introduced. Current best practices in computer networks load balancing are discussed as well. The load balancing application development process is described including the test laboratory setups - Mininet (SW) and OFELIA (HW). The application test results are evaluated and possible further enhancements to the program are discussed.

Choosing correct boundary conditions, flow field characteristics and employing right thermal fluid properties can affect the simulation of convection heat transfer using nanofluids. Nanofluids have shown higher heat transfer performance in comparison with conventional heat transfer fluids. The suspension of the nanoparticles in nanofluids creates a larger interaction surface to the volume ratio. Therefore, they can be distributed uniformly to bring about the most effective enhancement of heat transfer without causing a considerable pressure drop. These advantages introduce nanofluids as a desirable heat transfer fluid in the cooling and heating industries. The thermal effects of nanofluids in both forced and free convection flows have interested researchers to a great extent in the last decade. Investigating the interaction mechanisms happening between nanoparticles and base fluid is the main goal of the study. These mechanisms can be explained via different approaches through some theoretical and numerical methods. Two common approaches regarding particle-fluid interactions are Eulerian-Eulerian and Eulerian-Lagrangian. The dominant conceptions in each of them are slip velocity and interaction forces respectively. The mixture multiphase model as part of the Eulerian-Eulerian approach deals with slip mechanisms and somehow mass diffusion from the nanoparticle phase to the fluid phase. The slip velocity can be induced by a pressure gradient, buoyancy, virtual mass, attraction and repulsion between particles. Some of the diffusion processes can be caused by the gradient of temperature and concentration. The discrete phase model (DPM) is a part of the Eulerian-Lagrangian approach. The interactions between solid and liquid phase were presented as forces such as drag, pressure gradient force, virtual mass force, gravity, electrostatic forces, thermophoretic and Brownian forces. The energy transfer from particle to continuous phase can be introduced through both convective and conduction terms on the surface of the particles. A study of both approaches was conducted in the case of laminar and turbulent forced convections as well as cavity flow natural convection. The cases included horizontal and vertical pipes and a rectangular cavity. An experimental study was conducted for cavity flow to be compared with the simulation results. The results of the forced convections were evaluated with data from literature. Alumina and zinc oxide nanoparticles with different sizes were used in cavity experiments and the same for simulations. All the equations, slip mechanisms and forces were implemented in ANSYS-Fluent through some user-defined functions. The comparison showed good agreement between experiments and numerical results. Nusselt number and pressure drops were the heat transfer and flow features of nanofluid and were found in the ranges of the accuracy of experimental measurements. The findings of the two approaches were somehow different, especially regarding the concentration distribution. The mixture model provided more uniform distribution in the domain than the DPM. Due to the Lagrangian frame of the DPM, the simulation time of this model was much longer. The method proposed in this research could also be a useful tool for other areas of particulate systems. / Thesis (PhD)--University of Pretoria, 2016. / Mechanical and Aeronautical Engineering / PhD / Unrestricted

<div>Cloud and parallel computing are fundamental components in the processing of large data sets. Deployments of distributed computers require network infrastructure that is fast, efficient, and secure. Software Defined Networking (SDN) separates the forwarding of network data by switches (data plane) from the setting and managing of network policies (control plane). While this separation provides flexibility for setting network policies affecting the establishment of network flows in the data plane, it provides little to no fault tolerance for failures, either benign or caused by corrupted/malicious applications. Such failures can cause network flows to be incorrectly routed through the network or stop such flows altogether. Without protection against faults, cloud network providers using SDN run the risk of inefficient allocation of network resources or even data loss. Furthermore, the asynchronous nature existing protocols for SDN does not provide a mechanism for consistency in network policy updates across multiple switches.</div><div>In addition, cloud and parallel applications require an efficient means for accessing local system data (input data sets, temporary storage locations, etc.). While in many cases it may be possible for a process to access this data by making calls directly to a file system (FS) kernel driver, this is not always possible (e.g. when using experimental distributed FSs where the needed libraries for accessing the FS only exist in user space).</div><div>This dissertation provides a design for fault tolerance of SDN and infrastructure for advancing the performance of user space FSs. It is divided into three main parts. The first part describes a fault tolerant, distributed SDN control plane framework. The second part expands upon the fault tolerant approach to SDN control plane by providing a practical means for dynamic control plane membership as well as providing a simple mechanism for controller authentication through threshold signatures. The third part describes an efficient framework for user space FS access.</div><div>This research makes three contributions. First, the design, specification, implementation, and evaluation of a method for fault tolerant SDN control plane that is inter-operable with existing control plane applications involving minimal instrumentation of the data plane runtime. Second, the design, specification, implementation and evaluation of a mechanism for dynamic SDN control plane membership that all ensure consistency of network policy updates and minimizes switch overhead through the use of distributed key generation and threshold signatures. Third, the design, specification, implementation, and evaluation of a user space FS access framework that is correct to the Portable Operating System Interface (POSIX) specification with significantly better performance over existing user space access methods, while requiring no implementation changes for application programmers.</div>