5,435 research outputs found

    An Energy Aware and Secure MAC Protocol for Tackling Denial of Sleep Attacks in Wireless Sensor Networks

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    Wireless sensor networks which form part of the core for the Internet of Things consist of resource constrained sensors that are usually powered by batteries. Therefore, careful energy awareness is essential when working with these devices. Indeed,the introduction of security techniques such as authentication and encryption, to ensure confidentiality and integrity of data, can place higher energy load on the sensors. However, the absence of security protection c ould give room for energy drain attacks such as denial of sleep attacks which have a higher negative impact on the life span ( of the sensors than the presence of security features. This thesis, therefore, focuses on tackling denial of sleep attacks from two perspectives A security perspective and an energy efficiency perspective. The security perspective involves evaluating and ranking a number of security based techniques to curbing denial of sleep attacks. The energy efficiency perspective, on the other hand, involves exploring duty cycling and simulating three Media Access Control ( protocols Sensor MAC, Timeout MAC andTunableMAC under different network sizes and measuring different parameters such as the Received Signal Strength RSSI) and Link Quality Indicator ( Transmit power, throughput and energy efficiency Duty cycling happens to be one of the major techniques for conserving energy in wireless sensor networks and this research aims to answer questions with regards to the effect of duty cycles on the energy efficiency as well as the throughput of three duty cycle protocols Sensor MAC ( Timeout MAC ( and TunableMAC in addition to creating a novel MAC protocol that is also more resilient to denial of sleep a ttacks than existing protocols. The main contributions to knowledge from this thesis are the developed framework used for evaluation of existing denial of sleep attack solutions and the algorithms which fuel the other contribution to knowledge a newly developed protocol tested on the Castalia Simulator on the OMNET++ platform. The new protocol has been compared with existing protocols and has been found to have significant improvement in energy efficiency and also better resilience to denial of sleep at tacks Part of this research has been published Two conference publications in IEEE Explore and one workshop paper

    Markov Decision Processes with Applications in Wireless Sensor Networks: A Survey

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    Wireless sensor networks (WSNs) consist of autonomous and resource-limited devices. The devices cooperate to monitor one or more physical phenomena within an area of interest. WSNs operate as stochastic systems because of randomness in the monitored environments. For long service time and low maintenance cost, WSNs require adaptive and robust methods to address data exchange, topology formulation, resource and power optimization, sensing coverage and object detection, and security challenges. In these problems, sensor nodes are to make optimized decisions from a set of accessible strategies to achieve design goals. This survey reviews numerous applications of the Markov decision process (MDP) framework, a powerful decision-making tool to develop adaptive algorithms and protocols for WSNs. Furthermore, various solution methods are discussed and compared to serve as a guide for using MDPs in WSNs

    Applying frequency scanning arrays for time-efficient analog beam probing in multi-user hybrid beamforming systems

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    Next generation of mobile communications will have to cover the unceasingly growing demand of higher data rates and reliable services. In this situation it will be a must to migrate towards higher frequencies in the range of millimeter waves (mm-Waves), where there is plenty of available bandwidth, that would allow high data rates. However, for this new range of the spectrum the attenuation suffered is very strong. Therefore, the isotropic antennas used for lower frequencies are going to be replaced for highly directive ones in order to compensate for this effect. But at the same time the use of narrow beam will introduce a new problematic aspect that was previously inexistent, which is beam selection and beam alignment. In order to address this situation, efficient beamforming and beam alignment becomes critical. The ultimate aim of this thesis is to test Frequency Scanning Arrays (FSA) for analog beam probing techniques in multi-user hybrid beamforming systems. In order to achieve it, several previous steps have been made. This thesis is aiming to apply the technology of Frequency Scanning Arrays (FSA) in multiuser hybrid beamforming systems. First the analog beam probing using traditional Exhaustive Search (ES) is implemented, with not only hybrid but also analog and digital schemes. Also, several beam selection algorithms are defined and tested. Afterwards the effect of the channel estimation is considered and a timing delay for each user is implemented, in order to make the final comparison between ES and FSA as realistic as possible. The results obtained show that in most cases analised the FSA system outperforms the ES system. These encouraging results could be a good indicator that the use of FSA analog beam probing has many promising possibilities and has to be further investigated.La próxima generación de comunicaciones móviles tendrá que cubrir la incesantemente creciente demanda de mayores velocidades de transmisión datos y servicios fiables. En esta situación será imprescindible migrar hacia frecuencias más altas en el rango de las ondas milimétricas (mm-Waves), donde hay mucho ancho de banda disponible, que permitiría altas velocidades de transferencia de datos. Sin embargo, para este nuevo rango del espectro la atenuación sufrida es muy fuerte. Por ello, las antenas isotrópicas utilizadas para frecuencias más bajas van a ser sustituidas por otras muy directivas para compensar este efecto. Pero al mismo tiempo, el uso de un haz estrecho introducirá una nueva problemática que antes no existía, que es la selección y la alineación del haz. Para hacer frente a esta situación, una eficiente formación y alineación del haz se convierte en un aspecto fundamental. El objetivo final de esta tesis es probar los Frequency Scanning Arrays (FSA) para las técnicas de sondeo del haz analógico en sistemas de conformación de haz híbrido multiusuario. Para conseguirlo, se han realizado varios pasos previos. En esencia, en esta tesis se propone aplicar la tecnología de los Frequency Scanning Arrays (FSA) en sistemas multiusuario. En primer lugar, se implementa el sondeo analógico del haz mediante la tradicional búsqueda exhaustiva (Exhaustive Search, ES) con esquemas no sólo híbridos sino también analógicos y digitales. Además, se definen y prueban varios algoritmos de selección de haz. Después se considera el efecto de la estimación del canal y se implementa un retardo temporal para cada usuario, con el fin de realizar la comparación final entre ES y FSA de la manera más realista posible. Los resultados obtenidos muestran que en la mayoría de los casos analizados el sistema FSA supera al sistema ES. Estos resultados alentadores podrían ser un buen indicador de que el uso del haz analógico FSA tiene prometedoras posibilidades y tiene que ser investigado más a fondo.La pròxima generació de comunicacions mòbils haurà de cobrir la incessant i creixent demanda d'altes velocitats de transmissió de dades i serveis cada cop més fiables. En aquesta situació serà imprescindible migrar cap a freqüències més altes en el rang de les ones mil·limètriques (mm-Waves), on hi ha un gran ample de banda disponible, que permetria altes velocitats de transferència de dades. Tot i això, per aquest nou rang de l'espectre, l'atenuació que pateix el senyal és molt gran. Per aquesta raó, les antenes isotròpiques utilitzades per a freqüències més baixes seran substituïdes per d'altres molt directives per a compensar aquest efecte. Però al mateix temps, l'ús d'un feix estret introduirà una nova problemàtica que abans no existia, que és la selecció i alineació del feix. Per fer front a aquesta situació, una formació i alineació eficient del feix esdevé un aspecte fonamental. L'objectiu final d'aquesta tesi és provar els Frequency Scanning Arrays (FSA) per a les tècniques de sondeig del feix analògic en sistemes de conformació de feix híbrid multiusuari. Per tal d'aconseguir-ho s'han dut a terme diversos passos previs. En essència, en aquesta tesi es proposa aplicar la tecnologia dels Frequency Scanning Arrays (FSA) en sistemes multiusuari. En primer lloc, s'implementa el sondeig analògic del feix mitjançant la cerca exhaustiva tradicional (Exhaustive Search, ES) amb esquemes no només híbrids sinó també analògics i digitals. A més a més, es defineixen i es proven diversos algoritmes de selecció de feix. Després es considera l'efecte de l'estimació del canal i s'implementa un retard temporal per a cada usuari, amb la finalitat de dur a terme la comparació final entre ES i FSA de la manera més realista possible. Els resultats obtinguts demostren que en la majoria dels casos analitzats el sistema FSA supera al sistema ES. Aquests resultats encoratjadors podrien ser un bon indicador que l'ús del feix analògic FSA ofereix possibilitats prometedores i ha de ser investigat més a fons

    Throughput Optimal Flow Allocation on Multiple Paths for Random Access Wireless Multi-hop Networks

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    In this paper we consider random access wireless multi-hop mesh networks with multi-packet reception capabilities where multiple flows are forwarded to the gateways through node disjoint paths. We address the issue of aggregate throughput-optimal flow rate allocation with bounded delay guarantees. We propose a distributed flow rate allocation scheme that formulates flow rate allocation as an optimization problem and derive the conditions for non-convexity for an illustrative topology. We also employ a simple model for the average aggregate throughput achieved by all flows that captures both intra- and inter-path interference. The proposed scheme is evaluated through NS-2 simulations. Our preliminary results are derived from a grid topology and show that the proposed flow allocation scheme slightly underestimates the average aggregate throughput observed in two simulated scenarios with two and three flows respectively. Moreover it achieves significantly higher average aggregate throughput than single path utilization in two different traffic scenarios examined.Comment: Accepted for publication at the 9th IEEE BROADBAND WIRELESS ACCESS WORKSHOP (BWA2013), IEEE Globecom 2013 Workshop

    Fuzzy based load and energy aware multipath routing for mobile ad hoc networks

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    Routing is a challenging task in Mobile Ad hoc Networks (MANET) due to their dynamic topology and lack of central administration. As a consequence of un-predictable topology changes of such networks, routing protocols employed need to accurately capture the delay, load, available bandwidth and residual node energy at various locations of the network for effective energy and load balancing. This paper presents a fuzzy logic based scheme that ensures delay, load and energy aware routing to avoid congestion and minimise end-to-end delay in MANETs. In the proposed approach, forwarding delay, average load, available bandwidth and residual battery energy at a mobile node are given as inputs to a fuzzy inference engine to determine the traffic distribution possibility from that node based on the given fuzzy rules. Based on the output from the fuzzy system, traffic is distributed over fail-safe multiple routes to reduce the load at a congested node. Through simulation results, we show that our approach reduces end-to-end delay, packet drop and average energy consumption and increases packet delivery ratio for constant bit rate (CBR) traffic when compared with the popular Ad hoc On-demand Multipath Distance Vector (AOMDV) routing protocol
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