In this research, a new reputation-based model is utilized to disincentivize collusion of defenders and attackers in Software Defined Networks (SDN), and also, to disincentivize dishonest mining strategies in Blockchain. In the context of SDN, the model uses the reputation values assigned to each entity to disincentivize collusion with an attacker. Our analysis shows that not-colluding actions become Nash Equilibrium using the reputationbased model within a repeated game setting. In the context of Blockchain and mining, we illustrate that by using the same socio-rational model, miners not only are incentivized to conduct honest mining but also disincentivized to commit to any malicious activities against other mining pools. We therefore show that honest mining strategies become Nash Equilibrium in our setting. This thesis is laid out in the following manner. In chapter 2 an introduction to game theory is provided followed by a survey of previous works in game theoretic network security, in chapter 3 a new reputation-based model is introduced to be used within the context of a Software Defined Network (SDN), in chapter 4 a reputation-based solution concept is introduced to force cooperation by each mining entity in Blockchain, and finally, in chapter 5, the concluding remarks and future works are presented. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

<p><p>In order to keep up with the increasing demand on speed and reliability in modern wireless systems, new standards have to be introduced. By using Multiple Input Multiple Output technology (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) technologies the performance can be increased dramatically. Forthcoming standards such as WLAN 802.11n, WiMax and 3GPP LTE are all taking advantage of MIMO technology. To perform realistic tests with these standards it is often not enough to run software simulations in for example Matlab. Instead, as many real world parameters as possible need to be included. This can be done using a testbed, like the LiUMIMO, that actually transmits and receives data through the air.</p><p>The LiUMIMO is designed as a Software Defined Radio (SDR), only the RF front end and the data log are implemented in hardware, while all signal processing will be performed in Matlab.</p></p>

Future Wireless Local Area Networks (WLANs) with high carrier frequencies and wide channels need a dense deployment of Access Points (APs) to provide good performance. In densely deployed WLANs associations of stations and handovers need to be managed more intelligently than today. This dissertation studies when and how a station should perform a handover and to which AP from a theoretical and a practical perspective. We formulate and solve optimization problems that allow to compute the optimal AP for each station in normal WLANs and WLANs connected via a wireless mesh backhaul. Moreover, we propose to use software defined networks and the OpenFlow protocol to optimize station associations, handovers and traffic rates. Furthermore, we develop new mechanisms to estimate the quality  of a link  between a station and an AP. Those mechanisms allow optimization algorithms to make better decisions about when to initiate a handover. Since handovers in today’s WLANs are slow and may disturb real-time applications such as video streaming, a faster procedure is developed in this thesis. Evaluation results from wireless testbeds and network simulations show that our architectures and algorithms significantly increase the performance of WLANs, while they are backward compatible at the same time.

Our research aims at contributing to the evolution of modern wireless communications and to the development of software-defined radio (SDR) and cognitive radio, in particular. It promotes a general resource management framework that facilitates the integration of computing and radio resource management. This dissertation discusses the need for computing resource management in software-defined and cognitive radios and introduces an SDR computing resource management framework with cognitive capabilities. The hard real-time computing requirements of software-defined digital signal processing chains (SDR applications), the associated radio propagation and quality of service (QoS) implications, and heterogeneous multiprocessor platforms with limited computing resources (SDR platforms) define the context of these studies. We examine heterogeneous computing techniques, multiprocessor mapping and scheduling in particular, and elaborate a flexible framework for the dynamic allocation and reallocation of computing resources for wireless communications. The framework should facilitate partial reconfigurations of SDR platforms, dynamic switches between radio access technologies (RATs), and service and QoS level adjustments as a function of the environmental conditions. It, therefore, assumes the facilities of the platform and hardware abstraction layer operating environment (P-HAL-OE). We suggest a modular framework, distinguishing between the computing system modeling and the computing resource management. Our modeling proposal is based on two computing resource management techniques, which facilitate managing the strict timing constraints of real-time systems. It is scalable and can account for many different hardware architectures and computing resource types. This work focuses on processing and interprocessor bandwidth resources and processing and data flow requirements. Our computing resource management approach consists of a general-purpose mapping algorithm and a cost function. The independence between the algorithm and the cost function facilitates implementing many different computing resource management policies. We introduce a dynamic programming based algorithm, the tw-mapping, where w controls the decision window. We present a general and parametric cost function, which guides the mapping process under the given resource constraints. An instance of it facilitates finding a mapping that meets all processing and data flow requirements of SDR applications with the available processing and bandwidth resources of SDR platforms. Several SDR reconfiguration scenarios and analyses based on simulations demonstrate the suitability and potentials of our framework for a flexible computing resource management. We extend our SDR computing resource management concepts to the cognitive radio context. The two primary objectives of cognitive radio are highly reliable communications whenever and wherever needed and the efficient use of the radio spectrum. We formulate a third objective as the efficient use of computing resources. We analyze the cognitive capabilities of our framework─the cognitive radio’s interface to SDR platforms─and indicate the potentials of our cognitive computing resource management proposal. The cognitive computing resource management needs to be coordinated with the radio resource management. We, therefore, introduce the joint resource management concept for cognitive radios. We present three cognitive cycles and discuss several interrelations between the radio, computing, and application resources, where application resources refer to the available SDR and user applications. Our approach potentiates flexibility and facilitates radio against computing resource tradeoffs. It promotes cognition at all layers of the wireless system for a cooperative or integrated resource management that may increase the performance and efficiency of wireless communications. / El objetivo de las investigaciones que se están llevando a cabo dentro del grupo de investigación es contribuir a la evolución de las radiocomunicaciones modernas y, en particular, al desarrollo de los conceptos software radio (SDR) y cognitive radio. El planteamiento general es el de extender la flexibilidad global del sistema de comunicaciones planteando la definición y desarrollo de un entorno en el que pudiesen explorarse las relaciones entre la computación y las prestaciones del sistema de comunicaciones móviles facilitando la integración de los recursos de computación con los recursos radio. Dentro de este marco, la presente tesis plantea la discusión de la necesidad de la gestión de los recursos de computación en entornos SDR y cognitive radio y define un entorno de operación que asume las características especificas del concepto SDR a la vez que incorpora capacidades cognitivas en la gestión de los recursos de computación de las plataformas que den soporte a las nuevas generaciones de sistemas móviles. Los estrictos requerimientos de procesado en tiempo real de las cadenas de procesado digital de la señal definidas por software (aplicaciones SDR), las implicaciones asociadas con la propagación radio y el concepto de calidad de servicio (QoS) y plataformas heterogéneas de múltiples procesadores con recursos de computo limitados (plataformas SDR) definen el contexto de estos estudios. Se examinan técnicas de cómputo de propósito general para definir un entorno de operación que fuese capaz de asignar de forma flexible y dinámica los recursos de cómputo necesarios para facilitar las radiocomunicaciones a los niveles de QoS deseados. Ello debería facilitar los cambios dinámicos de una tecnología de acceso radio a otra, permitiendo el ajuste del tipo de servicio o calidad de servicio en función de las preferencias de los usuarios y las condiciones del entorno. Dicho entorno de operación asume las potencialidades del platform and hardware abstraction layer operating environment (P-HAL-OE). La estructura del entorno de operación se define de forma modular y consiste en un modelado genérico y flexible de las plataformas de computación SDR y en una gestión de recursos de computación abierta y capaz de ajustarse a diferentes objetivos y políticas. En el trabajo se exponen dos técnicas de gestión que pretenden asegurar la consecución estricta de los límites temporales típicos de los sistemas en tiempo real. En cuanto al modelado, este es escalable y capaz de capturar un amplio abanico de arquitecturas hardware y recursos de computación. En el presente trabajo nos centramos en los recursos y requerimientos del procesado y transferencia de datos. Se introduce un algoritmo de mapeo genérico e independiente de la función de coste. La independencia entre el algoritmo y la función de coste facilita la implementación de diferentes políticas de gestión de recursos computacionales. El tw-mapping es un algoritmo basado en dynamic programming, donde w controla la ventana de decisión. Se presenta una función de coste genérica y parametrizable que permite guiar el proceso de gestión de los recursos. Una instancia de ella facilita encontrar una solución al proceso de asignación de recursos que cumpla todos los requerimientos de procesado y trasferencia de datos de las aplicaciones SDR con los recursos disponibles de las plataformas SDR. Diferentes escenarios y varios análisis basados en simulaciones demuestran la adecuación del entorno de trabajo definido y desarrollado, así como sus potencialidades para una gestión flexible de los recursos de cómputo. Se extienden los conceptos mencionados previamente para entornos cognitive radio. Los principales objetivos del concepto cognitive radio son la disponibilidad de comunicaciones altamente robustas en cualquier lugar y momento en que sean necesarias y el uso eficiente del espectro. Como tercer objetivo formulamos el uso eficiente de los recursos de cómputo. Analizamos las capacidades cognitivas de nuestro entorno de operación─la interfaz del sistema cognitive radio a las plataformas SDR─y resaltamos las potencialidades de nuestra propuesta de gestión cognitiva de los recursos computacionales. Dicha gestión cognitiva de los recursos computacionales plantea una integración con la gestión de los recursos radio. Para ello introducimos el concepto de gestión de recursos conjunta para entornos cognitive radio. Se presentan tres ciclos cognitivos y se discuten algunas interrelaciones entre los recursos radio, de cómputo y de aplicación, donde los recursos de aplicación se refieren a las aplicaciones SDR y de usuario disponibles. Nuestra propuesta de gestión de recursos conjunta potencia la flexibilidad y facilita los intercambios entre recursos radio y de computación

Modern datacenters require a network with high cross-section bandwidth, fine-grained security, support for virtualization, and simple management that can scale to hundreds of thousands of hosts at low cost. This thesis first presents the firmware for Rain Man, a novel datacenter network architecture that meets these requirements, and then performs a general scalability study of the design space. The firmware for Rain Man, a scalable Software-Defined Networking architecture, employs novel algorithms and uses previously unused forwarding hardware. This allows Rain Man to scale at high performance to networks of forty thousand hosts on arbitrary network topologies. In the general scalability study of the design space of SDN architectures, this thesis identifies three different architectural dimensions common among the networks: source versus hop-by-hop routing, the granularity at which flows are routed, and arbitrary versus restrictive routing and finds that a source-routed, host-pair granularity network with arbitrary routes is the most scalable.

The evolution of wireless technology has necessitated the support of multiple communication standards by mobile devices. At present, multiple chipsets/radios operating at predefined sets of modulation schemes, frequency bands, bandwidths and output power levels are used to achieve this objective. This leads to higher component counts, increased cost and limits the capacity to cope with future communication standards. In order to tackle different wireless standards using a single chipset, digital circuits have been increasingly deployed in radios and demonstrated re-configurability in different modulation schemes (multimode) and frequency bands (multiband). Despite efforts and progress made in digitizing the entire radio, the power amplifier (PA) is still designed using an conventional approach and has become the bottleneck in digital transmitters, in terms of low average power efficiency, poor compatibility with modern CMOS technology and limited re-configurability. This research addresses these issues from two aspects. The first half of the thesis investigates signal encoding issues between the modulator and PA. We propose, analyze and evaluate a new hybrid amplitude/time signal encoding scheme that significantly improves the coding efficiency and dynamic range of a digitally modulated power amplifier (DMPA) without significantly increasing design complexity. The proposed hybrid amplitude/time encoding scheme combines both the amplitude domain and the time domain to optimally encode information. Experimental results show that hybrid amplitude/time encoding results in a 35% increase in the average coding efficiency with respect to conventional time encoding, and is only 6.7% lower than peak efficiency when applied to a Wireless Local Area Network (WLAN) signal with a peak to average power ratio equal to 9.9 dB. A new DMPA architecture, based on the proposed hybrid encoding, is also proposed. The second half of this thesis presents the design, analysis and implementation of a CMOS PA that is amenable to the proposed hybrid encoding scheme. A multi-way current mode class-D PA architecture has been proposed and realized in 130 nm CMOS technology. The designed PA has satisfied the objectives of wide bandwidth (1.5 GHz - 2.7 GHz at 1 dB output power), and high efficiency (PAE 63%) in addition to demonstrating linear responses using the proposed digital encoding. A complete digital transmitter combining the encoder and the multi-way PA was also investigated. The overall efficiency is 27% modulating 7.3 dB peak to average power ratio QAM signals.

Datacenters are a significant capital expense for many enterprises. Yet, they are difficult to manage and are hard to design and maintain. The initial design of a datacenter network tends to follow vendor guidelines, but subsequent upgrades and expansions to it are mostly ad hoc, with equipment being upgraded piecemeal after its amortization period runs out and equipment acquisition is tied to budget cycles rather than changes in workload. These networks are also brittle and inflexible. They tend to be manually managed, and cannot perform dynamic traffic engineering. The high-level goal of this dissertation is to reduce the total cost of owning a datacenter by improving its network. To achieve this, we make the following contributions. First, we develop an automated, theoretically well-founded approach to planning cost-effective datacenter upgrades and expansions. Second, we propose a scalable traffic management framework for datacenter networks. Together, we show that these contributions can significantly reduce the cost of operating a datacenter network. To design cost-effective network topologies, especially as the network expands over time, updated equipment must coexist with legacy equipment, which makes the network heterogeneous. However, heterogeneous high-performance network designs are not well understood. Our first step, therefore, is to develop the theory of heterogeneous Clos topologies. Using our theory, we propose an optimization framework, called LEGUP, which designs a heterogeneous Clos network to implement in a new or legacy datacenter. Although effective, LEGUP imposes a certain amount of structure on the network. To deal with situations when this is infeasible, our second contribution is a framework, called REWIRE, which using optimization to design unstructured DCN topologies. Our results indicate that these unstructured topologies have up to 100-500\% more bisection bandwidth than a fat-tree for the same dollar cost. Our third contribution is two frameworks for datacenter network traffic engineering. Because of the multiplicity of end-to-end paths in DCN fabrics, such as Clos networks and the topologies designed by REWIRE, careful traffic engineering is needed to maximize throughput. This requires timely detection of elephant flows---flows that carry large amount of data---and management of those flows. Previously proposed approaches incur high monitoring overheads, consume significant switch resources, or have long detection times. We make two proposals for elephant flow detection. First, in the Mahout framework, we suggest that such flows be detected by observing the end hosts' socket buffers, which provide efficient visibility of flow behavior. Second, in the DevoFlow framework, we add efficient stats-collection mechanisms to network switches. Using simulations and experiments, we show that these frameworks reduce traffic engineering overheads by at least an order of magnitude while still providing near-optimal performance.

The superior reconfigurability of software defined radio mobile devices has made it one of the most promising technology on the wireless network and in the mobile communication industry. The evolution from a static and rigid system to a highly dynamic environment, which offers many advantages over current systems, has been made possible thanks to the concepts of programmability and reconfigurability introduced by the software defined radio technology and the higher level of flexibility and openness of this technology's devices. Clearly, the software defined radio mobile device's flexibility is a great advantage since the customer is able to use the same device in different parts of the world, with different wireless technologies. Despite the advantages, there are still issues to be discussed regarding security. According to the Software Defined Radio Forum some of the concerns are the radio configuration download, storage and installation, user's privacy, and cloning. To address the SDR Forum concerns a raud-prevention framework is proposed. The framework is composed by new pieces of hardware, new modules and new protocols that together greatly enhance the overall security of software defined radio mobile devices and this new highly dynamic environment. The framework offers security monitoring against malicious attacks and viruses that may affect the configuration data; protects sensitive information through the use of protected storage; creates and protects an identity for the system; employs a secure and efficient protocol for radio configuration download and update; and finally, establishes an anti-cloning scheme, which not only guarantees that no units can be cloned over the air but also elevates the level of difficulty to clone units if the attacker has physical access to those units. Even if cloned units exist, the anti-cloning scheme is able to identify them and deny any service.

The recent popularity and convenience of Wireless communication and the need for integration demands the development of Software Defined Radio (SDR). First defined by Mitoal, the SDR processed the entire bandwidth using a high resolution and high speed ADC and remaining operations were done in DSP. The current trend in SDRs is to design highly reconfigurable analog front ends which can handle narrow-band and wideband standards, one at a time. Charge sampling has been widely used in these architectures due to the built in antialiasing capabilities, jitter robustness at high signal frequencies and flexibility in filter design. This work proposed a 1GHz wideband front end aimed at SDR applications using Transform Domain (TD) sampling techniques. Frequency Domain (FD) sampling, a special case of TD sampling, efficiently parallelizes the signal for digital processing, relaxing the sampling requirements and enabling parallel digital processing at a much lower rate and is a potential candidate for SDR. The proposed front end converts the RF signal into current and then it is downconverted using passive mixers. The front end has five parallel paths, each acting on a part of the spectrum effectively parallelizing the front end and relaxing the requirements. An overlap introduced between successive integration windows for jitter robustness was exploited to create a novel sinc2 downsample by two filter topology. This topology was compared to a conventional topology and found to be equivalent and area efficient by about 44%. The proposed topology was used as a baseband filter for all paths in the front end. The chip was sent for fabrication in 45nm technology. The active area of the chip was 6:6mm2. The testing and measurement of the chip still remains to be done.

Developing a flexible receiver, which can be reconfigured to multiple standards, is the key to solving the problem of embedding numerous and ever-changing functionalities in mobile handsets. Difficulty in efficiently reconfiguring analog blocks of a receiver chain to multiple standards calls for moving the ADC as close to the antenna as possible so that most of the processing is done in DSP. Different standards are sampled at different frequencies and a programmable anti-aliasing filtering is needed here. Windowed integration samplers have an inherent sinc filtering which creates nulls at multiples of fs. The attenuation provided by sinc filtering for a bandwidth B is directly proportional to the sampling frequency fs and, in order to meet the anti-aliasing specifications, a high sampling rate is needed. ADCs operating at such a high oversampling rate dissipate power for no good use. Hence, there is a need to develop a programmable discrete-time down-sampling circuit with high inherent anti-aliasing capabilities. Currently existing topologies use large numbers of switches and capacitors which occupy a lot of area.A novel technique in reducing die area on a discrete-time sinc2 ↓2 filter for charge sampling is proposed. An SNR comparison of the conventional and the proposed topology reveals that the new technique saves 25 percent die area occupied by the sampling capacitors of the filter. The proposed idea is also extended to implement higher downsampling factors and a greater percentage of area is saved as the down-sampling factor is increased. The proposed filter also has the topological advantage over previously reported works of allowing the designers to use active integration to charge the capacitance, which is critical in obtaining high linearity. A novel technique to implement a discrete-time sinc3 ↓2 filter for windowed integration samplers is also proposed. The topology reduces the idle time of the integration capacitors at the expense of a small complexity overhead in the clock generation, thereby saving 33 percent of the die area on the capacitors compared to the currently existing topology. Circuit Level simulations in 45 nm CMOS technlogy show a good agreement with the predicted behaviour obtained from the analaysis.