Cognitive privacy for personal clouds

This paper proposes a novel Cognitive Privacy (CogPriv) framework that improves privacy of data sharing between Personal Clouds for different application types and across heterogeneous networks. Depending on the behaviour of neighbouring network nodes, their estimated privacy levels, resource availability, and social network connectivity, each Personal Cloud may decide to use different transmission network for different types of data and privacy requirements. CogPriv is fully distributed, uses complex graph contacts analytics and multiple implicit novel heuristics, and combines these with smart probing to identify presence and behaviour of privacy compromising nodes in the network. Based on sensed local context and through cooperation with remote nodes in the network, CogPriv is able to transparently and on-the-fly change the network in order to avoid transmissions when privacy may be compromised. We show that CogPriv achieves higher end-to-end privacy levels compared to both noncognitive cellular network communication and state-of-the-art strategies based on privacy-aware adaptive social mobile networks routing for a range of experiment scenarios based on real-world user and network traces. CogPriv is able to adapt to varying network connectivity and maintain high quality of service while managing to keep low data exposure for a wide range of privacy leakage levels in the infrastructure

Cooperative smartphone relay selection based on fair power utilization for network coverage extension

This paper presents a relay selection algorithm based on fair battery power utilization for extending mobile network coverage and capacity by using a cooperative communication strategy where mobile devices can be utilized as relays. Cooperation improves the network performance for mobile terminals, either by providing access to out-of-range devices or by facilitating multi-path network access to connected devices. In this work, we assume that all mobile devices can benefit from using other mobile devices as relays and investigate the fairness of relay selection algorithms. We point out that signal strength based relay selection inevitably leads to unfair relay selection and devise a new algorithm that is based on fair utilization of power resources on mobile devices. We call this algorithm Credit based Fair Relay Selection (CF-RS) and in this paper show through simulation that the algorithm results in fair battery power utilization, while providing similar data rates compared with traditional approaches. We then extend the solution to demonstrate that adding incentives for relay operation adds clear value for mobile devices in the case they require relay service. Typically, mobile devices represent self-interested users who are reluctant to cooperate with other network users, mainly due to the cost in terms of power and network capacity. In this paper, we present an incentive based solution which provides clear mutual benefit for mobile devices and demonstrate this benefit in the simulation of symmetric and asymmetric network topologies. The CF-RS algorithm achieves the same performance in terms of achievable data rate, Jain's fairness index and utility of end devices in both symmetric and asymmetric network configurations

INDIGO: An In Situ Distributed Gossip Framework for Sensor Networks

Abstract—With the onset of Cyber-Physical Systems (CPS), distributed algorithms on Wireless Sensor Networks(WSNs) have been receiving renewed attention. The distributed consensus problem is a well studied problem having a myriad of applications which can be accomplished using asynchronous distributed gossip algorithms on Wireless Sensor Networks(WSN). However, a practical realization of gossip algorithms for WSNs is found lacking in the current state of the art. In this paper, we propose the design, development and analysis of a novel in-situ distributed gossip framework called INDIGO. A key aspect of INDIGO is its ability to execute on a generic system platform as well as on a hardware oriented testbed platform in a seamless manner allowing easy portability of existing algorithms. We evaluate the performance of INDIGO with respect to the distributed consensus problem as well as the distributed optimization problem. We also present a data driven analysis of the effect, certain operating parameters like sleep time and wait time have on the performance of the framework and empirically attempt to determine a sweet spot. The results obtained from various experiments on INDIGO validate its efficacy, reliability and robustness and demonstrate its utility as a framework for the evaluation and implementation of asynchronous distributed algorithms

Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions.

Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node's cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted

Experimental evaluation of a UWB-based cooperative positioning system for pedestrians in GNSS-denied environment

Cooperative positioning (CP) utilises information sharing among multiple nodes to enable positioning in Global Navigation Satellite System (GNSS)-denied environments. This paper reports the performance of a CP system for pedestrians using Ultra-Wide Band (UWB) technology in GNSS-denied environments. This data set was collected as part of a benchmarking measurement campaign carried out at the Ohio State University in October 2017. Pedestrians were equipped with a variety of sensors, including two different UWB systems, on a specially designed helmet serving as a mobile multi-sensor platform for CP. Different users were walking in stop-and-go mode along trajectories with predefined checkpoints and under various challenging environments. In the developed CP network, both Peer-to-Infrastructure (P2I) and Peer-to-Peer (P2P) measurements are used for positioning of the pedestrians. It is realised that the proposed system can achieve decimetre-level accuracies (on average, around 20 cm) in the complete absence of GNSS signals, provided that the measurements from infrastructure nodes are available and the network geometry is good. In the absence of these good conditions, the results show that the average accuracy degrades to meter level. Further, it is experimentally demonstrated that inclusion of P2P cooperative range observations further enhances the positioning accuracy and, in extreme cases when only one infrastructure measurement is available, P2P CP may reduce positioning errors by up to 95%. The complete test setup, the methodology for development, and data collection are discussed in this paper. In the next version of this system, additional observations such as the Wi-Fi, camera, and other signals of opportunity will be included

Contributions to the routing of traffic flows in multi-hop IEEE 802.11 wireless networks

The IEEE 802.11 standard was not initially designed to provide multi-hop capabilities. Therefore, providing a proper traffic performance in Multi-Hop IEEE 802.11 Wireless Networks (MIWNs) becomes a significant challenge. The approach followed in this thesis has been focused on the routing layer in order to obtain applicable solutions not dependent on a specific hardware or driver. Nevertheless, as is the case of most of the research on this field, a cross-layer design has been adopted. Therefore, one of the first tasks of this work was devoted to the study of the phenomena which affect the performance of the flows in MIWNs. Different estimation methodologies and models are presented and analyzed. The first main contribution of this thesis is related to route creation procedures. First, FB-AODV is introduced, which creates routes and forwards packets according to the flows on the contrary to basic AODV which is destination-based. This enhancement permits to balance the load through the network and gives a finer granularity in the control and monitoring of the flows. Results showed that it clearly benefits the performance of the flows. Secondly, a novel routing metric called Weighted Contention and Interference routing Metric (WCIM) is presented. In all analyzed scenarios, WCIM outperformed the other analyzed state-of-the-art routing metrics due to a proper leveraging of the number of hops, the link quality and the suffered contention and interference. The second main contribution of this thesis is focused on route maintenance. Generally, route recovery procedures are devoted to the detection of link breaks due to mobility or fading. However, other phenomena like the arrival of new flows can degrade the performance of active flows. DEMON, which is designed as an enhancement of FB-AODV, allows the preemptive recovery of degraded routes by passively monitoring the performance of active flows. Results showed that DEMON obtains similar or better results than other published solutions in mobile scenarios, while it clearly outperforms the performance of default AODV under congestion Finally, the last chapter of this thesis deals with channel assignment in multi-radio solutions. The main challenge of this research area relies on the circular relationship between channel assignment and routing; channel assignment determines the routes that can be created, while the created routes decide the real channel diversity of the network and the level of interference between the links. Therefore, proposals which join routing and channel assignment are generally complex, centralized and based on traffic patterns, limiting their practical implementation. On the contrary, the mechanisms presented in this thesis are distributed and readily applicable. First, the Interference-based Dynamic Channel Assignment (IDCA) algorithm is introduced. IDCA is a distributed and dynamic channel assignment based on the interference caused by active flows which uses a common channel in order to assure connectivity. In general, IDCA leads to an interesting trade-off between connectivity preservation and channel diversity. Secondly, MR-DEMON is introduced as way of joining channel assignment and route maintenance. As DEMON, MR-DEMON monitors the performance of the active flows traversing the links, but, instead of alerting the source when noticing degradation, it permits reallocating the flows to less interfered channels. Joining route recovery instead of route creation simplifies its application, since traffic patterns are not needed and channel reassignments can be locally decided. The evaluation of MR-DEMON proved that it clearly benefits the performance of IDCA. Also, it improves DEMON functionality by decreasing the number of route recoveries from the source, leading to a lower overhead.El estándar IEEE 802.11 no fue diseñado inicialmente para soportar capacidades multi-salto. Debido a ello, proveer unas prestaciones adecuadas a los flujos de tráfico que atraviesan redes inalámbricas multi-salto IEEE 802.11 supone un reto significativo. La investigación desarrollada en esta tesis se ha centrado en la capa de encaminamiento con el objetivo de obtener soluciones aplicables y no dependientes de un hardware específico. Sin embargo, debido al gran impacto de fenómenos y parámetros relacionados con las capas físicas y de acceso al medio sobre las prestaciones de los tráficos de datos, se han adoptado soluciones de tipo cross-layer. Es por ello que las primeras tareas de la investigación, presentadas en los capítulos iniciales, se dedicaron al estudio y caracterización de estos fenómenos. La primera contribución principal de esta tesis se centra en mecanismos relacionados con la creación de las rutas. Primero, se introduce una mejora del protocolo AODV, que permite crear rutas y encaminar paquetes en base a los flujos de datos, en lugar de en base a los destinos como se da en el caso básico. Esto permite balacear la carga de la red y otorga un mayor control sobre los flujos activos y sus prestaciones, mejorando el rendimiento general de la red. Seguidamente, se presenta una métrica de encaminamiento sensible a la interferencia de la red y la calidad de los enlaces. Los resultados analizados, basados en la simulación de diferentes escenarios, demuestran que mejora significativamente las prestaciones de otras métricas del estado del arte. La segunda contribución está relacionada con el mantenimiento de las rutas activas. Generalmente, los mecanismos de mantenimiento se centran principalmente en la detección de enlaces rotos debido a la movilidad de los nodos o a la propagación inalámbrica. Sin embargo, otros fenómenos como la interferencia y congestión provocada por la llegada de nuevos flujos pueden degradar de forma significativa las prestaciones de los tráficos activos. En base a ello, se diseña un mecanismo de mantenimiento preventivo de rutas, que monitoriza las prestaciones de los flujos activos y permite su reencaminamiento en caso de detectar rutas degradadas. La evaluación de esta solución muestra una mejora significativa sobre el mantenimiento de rutas básico en escenarios congestionados, mientras que en escenarios con nodos móviles obtiene resultados similares o puntualmente mejores que otros mecanismos preventivos diseñados específicamente para casos con movilidad. Finalmente, el último capítulo de la tesis se centra en la asignación de canales en entornos multi-canal y multi-radio con el objetivo de minimizar la interferencia entre flujos activos. El reto principal en este campo es la dependencia circular que se da entre la asignación de canales y la creación de rutas: la asignación de canales determina los enlaces existentes la red y por ello las rutas que se podrán crear, pero son finalmente las rutas y los tráficos activos quienes determinan el nivel real de interferencia que se dará en la red. Es por ello que las soluciones que proponen unificar la asignación de canales y el encaminamiento de tráficos son generalmente complejas, centralizadas y basadas en patrones de tráfico, lo que limita su implementación en entornos reales. En cambio, en nuestro caso adoptamos una solución distribuida y con mayor aplicabilidad. Primero, se define un algoritmo de selección de canales dinámico basado en la interferencia de los flujos activos, que utiliza un canal común en todos los nodos para asegurar la conectividad de la red. A continuación, se introduce un mecanismo que unifica la asignación de canales con el mantenimiento preventivo de las rutas, permitiendo reasignar flujos degradados a otros canales disponibles en lugar de reencaminarlos completamente. Ambas soluciones demuestran ser beneficiosas en este tipo de entornos.Postprint (published version

Improving the performance of wireless sensor networks using directional antennas

Over the last decades, lots of new applications have emerged thanks to the availability of small devices capable of wireless communications that form Wireless Sensor Networks (WSNs). These devices allow sensing, processing, and communication of multiple physical variables while keeping a low power consumption. During the last years, most of the research efforts were spent on the development and optimization of wireless communication protocols, aiming to maximize the reliability of the network while achieving the lowest possible power consumption. In this thesis, we study how to improve the performance of these WSNs by using directional antennas. Directional antennas can provide a higher gain and reduce the interference with other nodes by concentrating the radiated power in a certain direction. We present the different kinds of directional antennas available for WSNs, and we select the 6-element SPIDA antenna as a case of study. We present an electromagnetic model of this antenna, and we incorporate it into the COOJA network simulator. We report the first complete characterization of this antenna, including the radiation pattern and S11 parameters. The characterization shows that the antenna has a maximum gain of 6.8 dBi, a Half-Power Beamwidth (HPBW) of 113° and a module of S11 parameter of -7.5 dB at the central frequency (fc = 2.4525 GHz). We also present a novel way to optimize the antenna without changing its design by isolating multiple director elements. We show that with this technique, the performance of the antenna can be improved in terms of maximum gain, narrower HPBW, and a lower module of the S11 parameter without making any changes in the antenna itself. We evaluate the impact of supporting directional communications in the different layers of the network stack. We analyze the different challenges that arise and propose optimizations to overcome them in order to take advantage of the benefits of directional communication. We present an analysis of the state-of-the-art in neighbor discovery protocols for WSNs with directional antennas, and we propose, implement end evaluate two novel fully directional protocols: Q-SAND and DANDi. We compare both of them with SAND, a fully directional neighbor discovery protocol. DANDi is a fully directional asynchronous and dynamic neighbor discovery protocol where the contention resolution relies on a collision detection mechanism. To the best of our knowledge, DANDi is the fastest neighbor discovery protocol for WSN with directional antennas, with the additional advantage of being able to discover every reliable communication link in a network without requiring any prior information of the network topology. We combine the directional neighbor discovery protocol with MAC and routing optimizations in order fully take advantage of the benefits of using directional antennas. We focus on convergecast, a typical data collection application where every node sends packets periodically to a sink node. We present DirMAC, a novel MAC protocol that fully supports directional communication, together with four different heuristics to optimize the performance of the protocols. One of these heuristics has the added major benefit of being completely distributed and with no need for offline processing. Our evaluation shows that optimizations at both the MAC and routing layers are needed in order to reap the benefits of using directional antennas for convergecast. Our results show that the performance of the network can be greatly improved in terms of packet delivery rate, energy consumption, and energy per received packet, and that we obtain the largest performance improvements in networks with dense traffic. Simulations with different node densities show that when using directional antennas the PDR increases up to 29%, while energy consumption and energy per received packet decreases by up to 55% and 46% respectively. Experiments with real nodes validate these results showing a significant performance increase when using directional antennas in our scenarios, with a reduction in the RDC and EPRP of 25% and 15% respectively, while maintaining a PDR of 100%.Durante las últimas décadas, la disponibilidad de pequeños dispositivos con comunicación inalámbrica ha permitido el desarrollo de muchas nuevas aplicaciones. Estos dispositivos forman Redes de Sensores Inalámbricos (RSI, o WSN por sus siglas en inglés) que permiten sensar, procesar y comunicar datos provenientes de variables físicas, mientras que mantienen un bajo consumo energético. En los últimos años, la mayor parte de los esfuerzos de la comunidad científica estuvieron concentrados en el desarrollo y optimización de los protocolos de comunicación inalámbricos, buscando maximizar la confiabilidad de la red y minimizar el consumo energético. En esta tesis estudiamos cómo mejorar el rendimiento de las RSI usando antenas direccionales. Las antenas direccionales pueden proporcionar una mayor ganancia y reducir la interferencia con otros nodos al concentrar la potencia radiada en una cierta dirección. Comenzamos presentando los distintos tipos de antenas direccionales disponibles para las RSI, y seleccionamos la antena SPIDA de 6 elementos como caso de estudio. Luego presentamos un modelo electromagnético de la antena, que incorporamos al simulador de red COOJA. Construimos un primer prototipo con el que realizamos la primera caracterización completa de ésta antena, incluyendo el patrón de radiación y el parámetro S11. La caracterización muestra que la antena tiene una ganancia máxima de 6,8 dBi, un ancho de haz a mitad de potencia (HPBW por sus siglas en inglés) de 113° y un módulo del parámetro S11 de -7,5 dB en la frecuencia central (fc = 2,4525 GHz). También mostramos una forma innovadora de optimizar la antena sin cambiar su diseño utilizando varios elementos directores al mismo tiempo. Mostramos que con esta técnica se puede mejorar el rendimiento de la antena en términos de ganancia máxima, ancho de haz a mitad de potencia, y módulo del parámetro S11. Luego evaluamos el impacto de usar comunicaciones direccionales en las diferentes capas del stack de red. Analizamos los diferentes desafíos que surgen y proponemos optimizaciones para sortearlos. Presentamos un análisis del estado del arte en protocolos de descubrimiento de vecinos en RSI con antenas direccionales, y proponemos, implementamos y evaluamos dos protocolos direccionales : Q-SAND y DANDi. DANDi es un protocolo de descubrimiento de vecinos direccional, asíncrono y dinámico, donde la contienda por el canal se resuelve con un mecanismo basado en la detección de colisiones. Hasta donde sabemos, DANDi es el protocolo de descubrimiento de vecinos más rápido para RSI con antenas direccionales, con la ventaja adicional de que permite descubrir todos los enlaces de comunicación confiables de una red sin requerir ningún conocimiento previo de la topología. Luego combinamos los protocolos de descubrimiento de vecinos con optimizaciones en las capas de ruteo y acceso al medio para construir una aplicación de recolección de datos, donde cada nodo envía paquetes periódicamente a un nodo centralizador. Presentamos DirMAC, un protocolo de acceso al medio innovador que soporta comunicaciones direccionales, junto con cuatro heurísticas que permiten optimizar el rendimiento de los protocolos (una de ellas con la ventaja adicional que es totalmente distribuida). Los resultados muestran que usar antenas direccionales en este tipo de aplicaciones permite mejorar sustancialmente el rendimiento de la red, mostrando las mayores mejoras en redes con alto tráfico. Las simulaciones con diferentes densidades de nodos muestran que al usar antenas direccionales se puede aumentar el ratio de entrega de paquetes en hasta 29%, mientras que el consumo energético y la energía por paquete recibido bajan en hasta 55% y 46% respectivamente. Los experimentos en nodos reales validan estos resultados, mostrando una reducción en el consumo energético y en la energía por paquete recibido de 25% y 15% respectivamente, mientras que mantienen un ratio de entrega de paquetes de 100%