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Our world of people and objects is on the verge of transforming to a world of highly-interconnected wireless devices. Incredible advances in wireless communications, hardware design, and power storage have facilitated hasty spread of wireless technologies in human life. In this new world, individuals are often identified and reached via one or multiple wireless devices that they always carry (e.g., smartphones, smart wearable, implantable medical devices, etc.), and their biometrics identities are replaced by their digital fingerprints. In near future, vehicles will be controlled and monitored via wireless monitoring systems and various physical objects (e.g., home appliance and retail store items) will be connected to the Internet. The list of these changes goes on. Unfortunately, as different aspects of our lives are being immerged in and dependent to wireless devices and services, we will become more vulnerable to wireless service/connection interruptions due to adversarial behavior and our privacy will become more potent to be exposed to adversaries. An adversary can learn the procedures of a wireless system and analyze its stages, and accordingly, launch various attacks against the operations of the system or the privacy of the people. Existing data confidentiality and integrity services (e.g., advanced encryption algorithms) have been able to prevent the leakage of users' messages. However, in wireless networks, even when upper-layer payloads are encrypted, the users' privacy and the operation of a wireless network can be threatened by the leakage of transmission attributes at the physical (PHY) layer. Examples of these attributes are payload size, frequency offset (FO), modulation scheme, and the transmission rate. These attributes can be exploited by an adversary to launch passive or active attacks. A passive attacker may learn about the interests, sexual orientation, political views, and patentable ideas of the user through analyzing these features, whereas an active attacker exploits captured attributes to launch selective packet jamming/dropping and disrupt wireless services. These call for novel privacy preserving techniques beyond encryption. In this dissertation, we study the vulnerability of current wireless systems to the leakage of transmission attributes at the PHY layer and propose several schemes to prevent it. First, we design and experimentally demonstrate with USRPs an energy-efficient and highly disruptive jamming attack on the FO estimation of an OFDM system. OFDM is the core multiplexing scheme in many modern wireless systems (e.g., LTE/5G and 802.11a/n/ac) and is highly susceptible to FO. FO is the difference in the operating frequencies of two radio oscillators. This estimation is done by the receiver using the publicly-known frame preamble. We show that the leakage of FO value via the preamble can facilitate an optimally designed jamming signal without needing to know the channel between the transmitter and the legitimate receiver. Our results show that the jammer can guarantee a successful attack even when its power is slightly less than the transmitter's power. We then propose four mitigation approaches against the proposed FO attack. Next, we consider certain transmission attributes that are disclosed via unencrypted PHY/MAC headers. Example of these attributes are payload size, transmission rate, and MAC addresses. Beyond unencrypted headers, the adversary can estimate the frame size and transmission rate through identifying the payload's modulation scheme and measuring the transmission time. To prevent the leakage of these attributes, we propose Friendly CryptoJam scheme, which consists of three components: First, a modulation-aware encryption scheme to encrypt the headers. Second, an efficient modulation obfuscation techniques. Specifically, the proposed modulation obfuscation scheme embeds the modulation symbols of a frame's payload into the constellation of the highest-order modulation scheme supported by the system. Together with effective PHY/MAC header encryption at the modulation level, the proposed obfuscation scheme hides the transmission rate, payload size, and other attributes announced in the headers while avoiding any BER performance loss. Compared with prior art, Friendly CryptoJam enjoys less complexity and less susceptibility to FO estimation errors. The third component is a novel PHY-level identification method. To facilitate PHY/MAC header encryption when a MAC layer sender identifier cannot be used (e.g., due to MAC address encryption), we propose two preamble-based sender identification methods, one for OFDM and one for non-OFDM systems. A sender identifier is special message that can be embedded in the frame preamble. The extent of the applications of our embedding scheme goes beyond identifier embedding and include embedding part of the data frame, the sender's digital signature, or any meta-data that the sender provides. Our message embedding method can further be used to mitigate the FO estimation attack because the jammer can no longer optimize its jamming signal with respect to a fixed preamble signal. In addition, we considered friendly jamming technique in a multi-link/hop network to degrade the channels of the eavesdroppers and prevent successful decoding of the headers, while minimizing the required jamming power by optimally placing the friendly jamming devices.

Les réseaux de capteurs ont connu un grand essor ces dix dernières années. Ils interviennent dans tous les domaines de notre vie quotidienne et la rendent plus aisée. Malgré ce grand succès des réseaux de capteurs, plusieurs problèmes restent encore ouverts. La capacité énergétique et la fragilité du canal radio des réseaux de capteurs affectent gravement leurs performances. La communication coopérative représente une solution efficace pour lutter contre l'instabilité du canal radio et afin d'économiser plus d'énergie. Nous proposons dans ce manuscrit, d'utiliser la communication coopérative, en premier lieu, au niveau de la couche MAC afin de mettre en place un accès au canal coopératif et non égoïste. En second lieu, nous utilisons la communication coopérative au niveau de la couche réseau dans le but d'établir des chemins de routage plus stables et plus robustes. / Wireless sensor networks (WSN) have known a great development during the last decade. They intervene in all the domain of our everyday life to make it easier. Despite the success of WSN several problems have to be solved. The restricted energy capacity and the randomness of the wireless channel seriously affect the performances of the WSN. Cooperative communication represents an efficient solution to reduce the instability of the wireless channel and to optimize energy. In this thesis we propose to use cooperative communications at the MAC and network layer in order to set up a cooperative access to the channel and to establish more robust routing paths.

Recent development has lead to the emergence of distributed Wireless Sensor and Actor Networks (WSAN), which are capable of observing the physical environment, processing the data, making decisions based on the observations and performing appropriate actions. WSANs represent an important extension of Wireless Sensor Networks (WSNs) and may comprise a large number of sensor nodes and a smaller number of actor nodes. The sensor nodes are low-cost, low energy, battery powered devices with restricted sensing, computational and wireless communication capabilities. Actor nodes are resource richer with superior processing capabilities, higher transmission powers and a longer battery life. A basic operational scenario of a typical WSAN application follows the following sequence of events. The physical environment is periodically sensed and evaluated by the sensor nodes. The sensed data is then routed towards an actor node. Upon receiving sensed data, an actor node performs an action upon the physical environment if necessary, i.e. if the occurrence of a disturbance or critical event has been detected. The specific characteristics of sensor and actor nodes combined with some stringent application constraints impose unique requirements for WSANs. The fundamental challenges for WSANs are to achieve low latency, high energy efficiency and high reliability. The latency and energy efficiency requirements are in a trade-off relationship. The communication and coordination inside WSANs is managed via a Communication Protocol Stack (CPS) situated on every node. The requirements of low latency and energy efficiency have to be addressed at every layer of the CPS to ensure overall feasibility of the WSAN. Therefore, careful design of protocol layers in the CPS is crucial in attempting to meet the unique requirements and handle the abovementioned trade-off relationship in WSANs. The traditional CPS, comprising the application, network, medium access control and physical layer, is a layered protocol stack with every layer, a predefined functional entity. However, it has been found that for similar types of networks with similar stringent network requirements, the strictly layered protocol stack approach performs at a sub-optimal level with regards to network efficiency. A modern cross-layer paradigm, which proposes the employment of interactions between layers in the CPS, has recently attracted a lot of attention. The cross-layer approach promotes network efficiency optimization and promises considerable performance gains. It is found that in literature, the adoption of this cross-layer paradigm has not yet been considered for WSANs. In this dissertation, a complete cross-layer enabled WSAN CPS is developed that features the adoption of the cross-layer paradigm towards promoting optimization of the network efficiency. The newly proposed cross-layer enabled CPS entails protocols that incorporate information from other layers into their local decisions. Every protocol layer provides information identified as beneficial to another layer(s) in the CPS via a newly proposed Simple Cross-Layer Framework (SCLF) for WSANs. The proposed complete cross-layer enabled WSAN CPS comprises a Cross-Layer enabled Network-Centric Actuation Control with Data Prioritization (CL-NCAC-DP) application layer (APPL) protocol, a Cross-Layer enabled Cluster-based Hierarchical Energy/Latency-Aware Geographic Routing (CL-CHELAGR) network layer (NETL) protocol and a Cross-Layer enabled Carrier Sense Multiple Access with Minimum Preamble Sampling and Duty Cycle Doubling (CL-CSMA-MPS-DCD) medium access control layer (MACL) protocol. Each of these protocols builds on an existing simple layered protocol that was chosen as a basis for development of the cross-layer enabled protocols. It was found that existing protocols focus primarily on energy efficiency to ensure maximum network lifetime. However, most WSAN applications require latency minimization to be considered with the same importance. The cross-layer paradigm provides means of facilitating the optimization of both latency and energy efficiency. Specifically, a solution to the latency versus energy trade-off is given in this dissertation. The data generated by sensor nodes is prioritised by the APPL and depending on the delay-sensitivity, handled in a specialised manor by every layer of the CPS. Delay-sensitive data packets are handled in order to achieve minimum latency. On the other hand, delay-insensitive non critical data packets are handled in such a way as to achieve the highest energy efficiency. In effect, either latency minimization or energy efficiency receives an elevated precedence according to the type of data that is to be handled. Specifically, the cross-layer enabled APPL protocol provides information pertaining to the delay-sensitivity of sensed data packets to the other layers. Consequently, when a data packet is detected as highly delay-sensitive, the cross-layer enabled NETL protocol changes its approach from energy efficient routing along the maximum residual energy path to routing along the fastest path towards the cluster-head actor node for latency minimizing of the specific packet. This is done by considering information (contained in the SCLF neighbourhood table) from the MACL that entails wakeup schedules and channel utilization at neighbour nodes. Among the added criteria, the next-hop node is primarily chosen based on the shortest time to wakeup. The cross-layer enabled MACL in turn employs a priority queue and a temporary duty cycle doubling feature to enable rapid relaying of delay-sensitive data. Duty cycle doubling is employed whenever a sensor node’s APPL state indicates that it is part of a critical event reporting route. When the APPL protocol state (found in the SCLF information pool) indicates that the node is not part of the critical event reporting route anymore, the MACL reverts back to promoting energy efficiency by disengaging duty cycle doubling and re-employing a combination of a very low duty cycle and preamble sampling. The APPL protocol conversely considers the current queue size of the MACL and temporarily halts the creation of data packets (only if the sensed value is non critical) to prevent a queue overflow and ease congestion at the MACL By simulation it was shown that the cross-layer enabled WSAN CPS consistently outperforms the layered CPS for various network conditions. The average end-to-end latency of delay-sensitive critical data packets is decreased substantially. Furthermore, the average end-to-end latency of delay-insensitive data packets is also decreased. Finally, the energy efficiency performance is decreased by a tolerable insignificant minor margin as expected. The trivial increase in energy consumption is overshadowed by the high margin of increase in latency performance for delay-sensitive critical data packets. The newly proposed cross-layer CPS achieves an immense latency performance increase for WSANs, while maintaining excellent energy efficiency. It has hence been shown that the adoption of the cross-layer paradigm by the WSAN CPS proves hugely beneficial with regards to the network efficiency performance. This increases the feasibility of WSANs and promotes its application in more areas. / Dissertation (MEng)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted

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Approved for public release; distribution in unlimited. / OFDM is a modulation technique that achieves high data rates, increased bandwidth efficiency and robustness in multipath environments. However, OFDM has some disadvantages, such as sensitivity to channel fading, large peak to average ratio and sensitivity to frequency offset. The latter causes intercarrier interference (ICI) and a reduction in the amplitude of the desired subcarrier which results in loss of orthogonality. In this thesis, the effects of frequency offset are studied in terms of loss of orthogonality. A number of techniques for frequency offset estimation are presented and tested in computer simulations. / Lieutenant Junior Grade, Turkish Navy

Made available in DSpace on 2016-04-26T20:22:49Z (GMT). No. of bitstreams: 1 Carlos Augusto Alcantara Machado.pdf: 1837362 bytes, checksum: 989675495c83e4f542aac6415923d3a7 (MD5) Previous issue date: 2014-05-23 / The world, nowadays, searches a new civilizing mark. Freedom and equality, as achievements, respectively, of the Liberal State and of the Social State, no more fulfill the wishes of the contemporary state. We will present Fraternity, as the fundament of a new humanism, the unabridged humanism, which has its roots in Christian doctrine, but it also is a cultural element. That influences the elaboration of Law and changes it, bringing new paradigms. We will study Fraternity from the recognition of the equality of dignity of all human beings, in accordance to precepts particularly written in the Universal Declaration of Human Rights, but also in contemporary constitutional documents. We will analyze, specially, Brazilian Constitution of 1988, starting from the preamble, to, considering its hermeneutical force, but also normative force, conclude that Fraternity is not only a purely religious, philosophical or political value, but it is a legal category and has constitutional guarantees. Thus, we will present Fraternity as a point of equilibrium between traditionally assured principles as freedom and equality. In this line of approach the development of constitutionalism will permit, in humanity current stage, with the recognizing of the juridic category of fraternity, the flourishment of Fraternal Constitutionalism, indispensable element to assure to everyone the pursuit of happiness / O mundo, hoje, busca encontrar um novo marco civilizatório. A liberdade e a igualdade, como conquistas do Estado Liberal e do Estado Social, respectivamente, não mais atendem aos anseios do Estado contemporâneo. Apresentar-se-á a Fraternidade, como fundamento de um novo humanismo, o humanismo integral, que tem a sua raiz na doutrina cristã, mas se constitui em elemento cultural que influencia a elaboração do Direito e o transforma, trazendo novos paradigmas. Estudar-se-á a fraternidade partindo do reconhecimento da igualdade de dignidade de todos os seres humanos, conforme preceito consubstanciado particularmente na Declaração Universal dos Direitos do Homem, mas também em documentos constitucionais contemporâneos. Analisar-se-á, em especial, a Constituição brasileira de 1988, a partir do preâmbulo, para, considerando a sua força hermenêutica, mas também normativa, concluir-se que a fraternidade não é um valor de natureza puramente religiosa, filosófica ou política, mas é uma categoria jurídica e tem garantia constitucional. Assim, apresentar-se-á a fraternidade como ponto de equilíbrio entre princípios tradicionalmente assegurados como a liberdade e a igualdade. Nessa linha de abordagem o desenvolvimento do constitucionalismo possibilitará, no estágio atual da humanidade, com o reconhecimento da categoria jurídica da fraternidade, fazer florescer o Constitucionalismo Fraternal, elemento indispensável para garantir a todos a busca da felicidade

This diploma thesis deals with design and realization of a module for a digital signal procesor, for handheld RFID reader working in UHF band. It utilises a special chip EM4298 for RFID signals processing. Module is controlled by the microcontroller ATmega32L, which communicates with the PC through USB bus. Settings in EM4298 is made by a service program which processes received identifying data obtained from tags. Source codes for microcontroller are created in AVR Studio 4.13 program. Source codes for microcontroller are created in C++ Builder 6.0 program. Further thing is Desing and realization of analog interface and a UHF transceiver for wireless communication with tags. A Webench program was used for the analog interface design, which is freely available on the internet. For verification of parameters of the analog interface it was used PSpice 10.0 program. The UHF transceiver is build-up with a MAX2903 chip (transmitter) and AD8347 (receiver) and transmitting and receiving antennae.

Cette thèse se donne pour objet de tester, dans le contexte spécifique du droit français, la véracité et la pérennité des critiques féministe puis genrée de la définition du réfugié consistant à dénoncer la non-prise en compte des persécutions subies par les femmes et les minorités sexuelles dans le cadre de l’élection audit statut. Et c’est un constat mitigé qui ressort de l’étude car, en dépit des nombreuses pressions internationales et européennes invitant à une analyse genrée de la notion, ces critiques héritées des années 1980 apparaissent, dans une large mesure, encore d’actualité. Certes, le phénomène d’exclusion des persécutions liées au genre qu’elles dénonçaient s’est quelque peu affaibli, en ce que les persécutions subies par les femmes et les membres des minorités sexuelles ne sont, par principe, plus exclues du champ de la définition du réfugié. Mais il n’existe cependant toujours pas de volonté, politique ou juridictionnelle, visant à les intégrer pleinement dans l’analyse. En effet, les efforts consentis pour leur prise en compte se révèlent encore insuffisants, laissant demeurer des obstacles subtils à leur intégration, des obstacles d’autant plus délicats à identifier et à surmonter. / The purpose of this thesis is to test, in the specific context of French law, the veracity and durability of feminist and gendered review of the refugee definition, which consists in denouncing the failure to take into account persecutions suffered by women and sexual minorities in the election process. It is a mixed conclusion that emerges from the study because, despite the numerous international and European pressures calling for a gendered analysis of the concept, these criticisms inherited from the 1980s still appear, to a large extent, to be relevant. Admittedly, the exclusion of gender-related persecution that they denounced has somewhat weakened, because persecutions suffered by women and members of sexual minorities are no longer excluded, as a matter of principle, from the scope of the refugee definition. However, there is still no political or jurisdictional will to fully integrate them into the analysis. Indeed, the efforts made to take them into account are still insufficient, leaving subtle obstacles to their integration, obstacles that are all the more difficult to identify and overcome.