Energy-Efficient Querying of Wireless Sensor Networks

Due to the distributed nature of information collection in wireless sensor networks and the inherent limitations of the component devices, the ability to store, locate, and retrieve data and services with minimum energy expenditure is a critical network function. Additionally, effective search protocols must scale efficiently and consume a minimum of network energy and memory reserves. A novel search protocol, the Trajectory-based Selective Broadcast Query protocol, is proposed. An analytical model of the protocol is derived, and an optimization model is formulated. Based on the results of analysis and simulation, the protocol is shown to reduce the expected total network energy expenditure by 45.5 percent to 75 percent compared to current methods. This research also derives an enhanced analytical node model of random walk search protocols for networks with limited-lifetime resources and time-constrained queries. An optimization program is developed to minimize the expected total energy expenditure while simultaneously ensuring the proportion of failed queries does not exceed a specified threshold. Finally, the ability of the analytical node model to predict the performance of random walk search protocols in large-population networks is established through extensive simulation experiments. It is shown that the model provides a reliable estimate of optimum search algorithm parameters

PERFORMANCE ANALYSIS AND OPTIMIZATION OF QUERY-BASED WIRELESS SENSOR NETWORKS

This dissertation is concerned with the modeling, analysis, and optimization of large-scale, query-based wireless sensor networks (WSNs). It addresses issues related to the time sensitivity of information retrieval and dissemination, network lifetime maximization, and optimal clustering of sensor nodes in mobile WSNs. First, a queueing-theoretic framework is proposed to evaluate the performance of such networks whose nodes detect and advertise significant events that are useful for only a limited time; queries generated by sensor nodes are also time-limited. The main performance parameter is the steady state proportion of generated queries that fail to be answered on time. A scalable approximation for this parameter is first derived assuming the transmission range of sensors is unlimited. Subsequently, the proportion of failed queries is approximated using a finite transmission range. The latter approximation is remarkably accurate, even when key model assumptions related to event and query lifetime distributions and network topology are violated. Second, optimization models are proposed to maximize the lifetime of a query-based WSN by selecting the transmission range for all of the sensor nodes, the resource replication level (or time-to-live counter) and the active/sleep schedule of nodes, subject to connectivity and quality-of-service constraints. An improved lower bound is provided for the minimum transmission range needed to ensure no network nodes are isolated with high probability. The optimization models select the optimal operating parameters in each period of a finite planning horizon, and computational results indicate that the maximum lifetime can be significantly extended by adjusting the key operating parameters as sensors fail over time due to energy depletion. Finally, optimization models are proposed to maximize the demand coverage and minimize the costs of locating, and relocating, cluster heads in mobile WSNs. In these models, the locations of mobile sensor nodes evolve randomly so that each sensor must be optimally assigned to a cluster head during each period of a finite planning horizon. Additionally, these models prescribe the optimal times at which to update the sensor locations to improve coverage. Computational experiments illustrate the usefulness of dynamically updating cluster head locations and sensor location information over time

AN ENERGY EFFICIENT CROSS-LAYER NETWORK OPERATION MODEL FOR MOBILE WIRELESS SENSOR NETWORKS

Wireless sensor networks (WSNs) are modern technologies used to sense/control the environment whether indoors or outdoors. Sensor nodes are miniatures that can sense a specific event according to the end user(s) needs. The types of applications where such technology can be utilised and implemented are vast and range from households’ low end simple need applications to high end military based applications. WSNs are resource limited. Sensor nodes are expected to work on a limited source of power (e.g., batteries). The connectivity quality and reliability of the nodes is dependent on the quality of the hardware which the nodes are made of. Sensor nodes are envisioned to be either stationary or mobile. Mobility increases the issues of the quality of the operation of the network because it effects directly on the quality of the connections between the nodes

Biologically inspired, self organizing communication networks.

PhDThe problem of energy-efficient, reliable, accurate and self-organized target tracking in Wireless Sensor Networks (WSNs) is considered for sensor nodes with limited physical resources and abrupt manoeuvring mobile targets. A biologically inspired, adaptive multi-sensor scheme is proposed for collaborative Single Target Tracking (STT) and Multi-Target Tracking (MTT). Behavioural data obtained while tracking the targets including the targets’ previous locations is recorded as metadata to compute the target sampling interval, target importance and local monitoring interval so that tracking continuity and energy-efficiency are improved. The subsequent sensor groups that track the targets are selected proactively according to the information associated with the predicted target location probability such that the overall tracking performance is optimized or nearly-optimized. One sensor node from each of the selected groups is elected as a main node for management operations so that energy efficiency and load balancing are improved. A decision algorithm is proposed to allow the “conflict” nodes that are located in the sensing areas of more than one target at the same time to decide their preferred target according to the target importance and the distance to the target. A tracking recovery mechanism is developed to provide the tracking reliability in the event of target loss. The problem of task mapping and scheduling in WSNs is also considered. A Biological Independent Task Allocation (BITA) algorithm and a Biological Task Mapping and Scheduling (BTMS) algorithm are developed to execute an application using a group of sensor nodes. BITA, BTMS and the functional specialization of the sensor groups in target tracking are all inspired from biological behaviours of differentiation in zygote formation. Simulation results show that compared with other well-known schemes, the proposed tracking, task mapping and scheduling schemes can provide a significant improvement in energy-efficiency and computational time, whilst maintaining acceptable accuracy and seamless tracking, even with abrupt manoeuvring targets.Queen Mary university of London full Scholarshi

Performance evaluation of Vehicular Ad Hoc Networks over high speed environment using NCTUns

Català: Cada any aproximadament un milió dues-centes mil persones moren en accidents de trànsit. D'aquesta dada es desprèn que els accidents de trànsit són la quarta causa de mortalitat al món. Degut a això, un gran nombre de governs i els majors fabricants de vehicles del món estan invertint temps i diners en recerca i desenvolupament per millorar la seguretat a les carreteres. Amb aquest objectiu, apareix el concepte de VANET: Vehicular Ad-hoc NETwork. Una VANET està basada en vehicles i estacions base intel·ligents que comparteixen informació a través de comunicacions inalàmbriques. Aquest intercanvi de dades podria tenir un gran impacte en la seguretat viària i la qualitat en la conducció però a més a més seria una nova font d' entreteniment mòbil. La millora en seguretat implicaria una reducció en el nombre d'accidents i les comunicacions inalàmbriques usades en mobilitat permetrien una optimització del transport. L'evolució de les VANETs en els últims anys i les seves aplicacions útils a les carreteres són les principals raons per dur a terme aquest projecte. El gran suport a aquest tipus de xarxes inalàmbriques sembla indicar que les VANETs són les xarxes del futur en entorns mòbils. En relació al projecte, el primer problema observat és que el protocol que s'usa específicament en VANETs (802.11p) només està disponible en pocs simuladors de xarxa i està en fase de desenvolupament. Per tant, la majoria de les funcions no estan implementades i això fa que el protocol no sigui madur. En conseqüència, es va triar un protocol àmpliament usat com és 802.11b per fer les proves en el simulador NCTUns. L?objectiu del projecte és avaluar el funcionament de VANETs usant el protocol 802.11b i el protocol d?encaminament AODV en un escenari d?autopista. Ajustant diferents paràmetres com el nombre de cotxes, la seva velocitat i el seu rang de cobertura és possible obtenir variacions en les mesures de pèrdues, throughput i retard extrem-a-extrem en la xarxa. El resultat final és que les mesures permeten saber quines són les comunicacions que es produeixen a la xarxa per cadascuna de les configuracions i la seva incidència en les condicions de conducció.Castellano: Cada año cerca de un millón doscientas mil personas fallecen en accidentes de tráfico. De este dato se desprende que los accidentes de tráfico son la cuarta causa de mortalidad en el mundo. Debido a esto, un gran número de gobiernos y los mayores fabricantes de vehículos del mundo están invirtiendo tiempo y dinero en investigación y desarrollo para mejorar la seguridad en las carreteras. Con este objetivo, aparece el concepto de VANET: Vehicular Ad-hoc NETwork. Una VANET se basa en vehículos y estaciones base inteligentes que comparten información por medio de comunicaciones inalámbricas. Este intercambio de datos podría tener un gran impacto en la seguridad vial y en la calidad de la conducción pero además sería una nueva fuente de entretenimiento móvil. La mejora en la seguridad implicaría una reducción en el número de accidentes y las comunicaciones inalámbricas utilizadas en movilidad permitirían optimizar el transporte. La evolución de las VANETs en los últimos años y sus aplicaciones útiles en las carreteras son las principales razones para llevar a cabo este proyecto. El gran apoyo a este tipo de redes inalámbricas parece indicar que las VANETs son las redes del futuro en entornos móviles. En relación al proyecto, el primer problema observado es que el protocolo específicamente utilizado en VANETs (802.11p) sólo está disponible en pocos simuladores de red y se encuentra en fase de desarrollo. Por lo tanto, la mayoría de funciones no están implementadas y esto hace que el protocolo no sea maduro. En consecuencia, se escogió un protocolo ampliamente utilizado como es 802.11b para realizar las pruebas en el simulador NCTUns. El objetivo del proyecto es evaluar el funcionamiento de VANETs utilizando el protocolo 802.11b y el protocolo de encaminamiento AODV en un escenario de autopista. Ajustando diferentes parámetros como el número de coches, su velocidad y su rango de cobertura es posible obtener variaciones en las medidas de pérdidas, throughput y retardo extremo-a-extremo en la red. El resultado final es que las medidas permiten saber cuáles son las comunicaciones que se producen en la red para cada una de las configuraciones y su incidencia en las condiciones de conducción.English: Every year about 1.2 million people die because of traffic accidents [1]. This means that traffic accidents are the fourth cause of mortality in the world. Therefore, several governments and the most important car manufacturers are investing time and money on research and development in order to improve road safety. At this respect, appears the concept of VANET: Vehicular Ad-hoc NETwork. A VANET is based on smart cars and base-stations that share information via wireless communications. This interchange of data may have a great impact on safety and driving quality but also could be another source of mobile entertainment. This improvement on safety would imply reducing the number of accidents. In addition, the use of wireless communications in mobility would lead to an optimization of transport. The evolution of VANETs in the last years and their useful applications on the road has been the main reason to develop this project. The great support of many people to this type of wireless networks suggests that VANETs are the networks of the future in mobile environments. Regarding the project, the first problem encountered is that the network protocol specially designed for VANETs, IEEE 802.11p, is only available in a few of the network simulators and is on phase of development. This fact means that most of the functions are not implemented so it cannot be considered as a mature protocol. As a consequence, a widely used protocol as IEEE 802.11b was chosen and all the tests were performed on NCTUns simulator. So the purpose of this project is to evaluate the performance of VANETs by using 802.11b protocol and AODV routing protocol in a highway scenario. By adjusting different parameters like number of cars, their speed and their range of coverage, variations on measures of loss ratio, throughput and end-to- end delay were detected on the network. Finally, the measures help to know about network communications for each of the cases and their incidence on driving conditions

AN ENERGY EFFICIENT CROSS-LAYER NETWORK OPERATION MODEL FOR MOBILE WIRELESS SENSOR NETWORKS

Wireless sensor networks (WSNs) are modern technologies used to sense/control the environment whether indoors or outdoors. Sensor nodes are miniatures that can sense a specific event according to the end user(s) needs. The types of applications where such technology can be utilised and implemented are vast and range from households’ low end simple need applications to high end military based applications. WSNs are resource limited. Sensor nodes are expected to work on a limited source of power (e.g., batteries). The connectivity quality and reliability of the nodes is dependent on the quality of the hardware which the nodes are made of. Sensor nodes are envisioned to be either stationary or mobile. Mobility increases the issues of the quality of the operation of the network because it effects directly on the quality of the connections between the nodes

Cross layer based protocols for energy aware and critical data delivery related applications using wireless sensor networks

Wireless Sensor Networks (WSNs) have been an exciting topic in recent years. The services offered by a WSN can be classified into three major categories: monitoring, alerting, and information on demand. WSNs have been used for a variety of applications related to the environment (agriculture, water and forest fire detection), the military, buildings, health (elderly people and home monitoring), disaster relief, and area or industrial monitoring. In most WSNs tasks like processing the sensed data, making decisions and generating emergency messages are carried out by a remote server, hence the need for efficient means of transferring data across the network. Because of the range of applications and types of WSN there is a need for different kinds of MAC and routing protocols in order to guarantee delivery of data from the source nodes to the server (or sink). In order to minimize energy consumption and increase performance in areas such as reliability of data delivery, extensive research has been conducted and documented in the literature on designing energy efficient protocols for each individual layer. The most common way to conserve energy in WSNs involves using the MAC layer to put the transceiver and the processor of the sensor node into a low power, sleep state when they are not being used. Hence the energy wasted due to collisions, overhearing and idle listening is reduced. As a result of this strategy for saving energy, the routing protocols need new solutions that take into account the sleep state of some nodes, and which also enable the lifetime of the entire network to be increased by distributing energy usage between nodes over time. This could mean that a combined MAC and routing protocol could significantly improve WSNs because the interaction between the MAC and network layers lets nodes be active at the same time in order to deal with data transmission. In the research presented in this thesis, a cross-layer protocol based on MAC and routing protocols was designed in order to improve the capability of WSNs for a range of different applications. Simulation results, based on a range of realistic scenarios, show that these new protocols improve WSNs by reducing their energy consumption as well as enabling them to support mobile nodes, where necessary. A number of conference and journal papers have been published to disseminate these results for a range of applications

A Novel Communication Approach For Wireless Mobile Smart Objects

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2007Telsiz ağlar gezgin kullanıcılara nerede olduklarına bağlı olmadan her yerde iletişim kurma ve bilgiye erişim imkanı sağlar. Hiçbir sabit altyapıya gerek duymadan bu imkanı sağlayan tasarsız ağların zaman içinde gelişmesiyle, askeri, ticari ve özel maksatlar için tercih edilir hale gelmiştir. Diğer yandan, bilimsel ve teknolojik gelişmeler ağ elemanlarını daha küçük ve ucuz hale getirdikçe birçok uygulamanın vazgeçilmez parçaları olmuşlardır. Bu ağ elemanları, taşıyıcılara (örneğin gemiler, uçaklar, büyük araçlar, arabalar, insanlar, hayvanlar, vb.) monteli nesneler veya kendi taşıyıcısı olan (aktörler, duyargalar) nesneler olabilir. Fakat bu ağ elemanları ve uygulamalarında bir takım zorluklar yaşanmaktadır. Bu tezde, gezgin tasarsız ve duyarga ağlardaki yaşanan zorlukları ve beklentileri dikkate alarak, gezgin tasarsız ve duyarga ağlar için yeni bir özgün, durumsuz veri akış yaklaşımı ve yönlendirme algoritması önerilmektedir. Durumsuz Ağırlıklı Yönlendirme (DAY, “Stateless Weighted Routing – SWR”) algoritması olarak adlandırdığımız bu algoritma, diğer yöntemlere göre daha az yönlendirme yükü, daha az enerji tüketimi, daha az yol oluşturma gecikmesi sağlamaktadır. Veri, varışa doğru, çoklu yollar üzerinden taşınmaktadır. Çoklu yol oluşturma, güvenirliği sağlamakta, boşluk problemini büyük oranda çözmekte ve en kısa yolu da içeren daha gürbüz yollar oluşmasını sağlamaktadır. DAY aynı zamanda büyük ölçekli ağlarda da uygulanabilir. Bu amaçla, birden fazla veri toplanma düğümü (sink) içeren sürümü olan Çoklu Veri Toplanma Düğümlü- Durumsuz Ağırlıklı Yönlendirme (ÇVTD-DAY - “Multiple Sink-Stateless Weighted Routing - MS-SWR”) yöntemi de büyük ölçekli tasarsız ve duyarga ağları için önerilmiştir. ÇVTD-DAY yöntemi, DAY yönteminde herhangi bir yöntemsel ve algoritmik değişiklik yapmadan birden fazla veri toplanma düğümünün olduğu ağlarda uygulanabilir. Hem DAY, hem ÇVTD-DAY’nin başarımı benzetimler ile ölçüldü. Elde edilen sonuçlar, DAY ‘nin gezgin tasarsız ve duyarga ağlar için istenenleri karşıladığını, karşılaştırılan diğer yöntemlere göre üstün olduğunu ve olası en iyi çözüme yakınlığını, öte yandan ÇVTD-DAY‘nin de büyük ölçekli ağlarda uygulanabilir olduğunu göstermektedir.Wireless networks provide mobile user with ubiquitous communication capability and information access regardless of location. Mobile ad hoc networks, that manage it without a need to infrastructure networks, as evolved in time, become more preferable for military, commercial and special purposes. On the other hand, technological advances made network components smaller and cheaper. These network components involves a wide variety of objects such as objects mounted on crafts/platforms (e.g. ships, aircrafts, trucks, cars, humans, animals), and objects that have their own platforms (e.g. actuators, sensor nodes). However, these network components and their involved applications exhibit some challenges to implement. By considering the challenges and expectations of mobile ad hoc networks and sensor network, we propose a novel stateless data flow approach and routing algorithm namely Stateless Weighted Routing (SWR) for mobile ad hoc and sensor networks. The SWR has low routing overhead providing very low energy consumption, and has low route construction delay than other proposed schemes. Multiple paths to the destination are established for data transmission. Constructing multiple paths provides reliability, eliminates the void problem substantially, and provides more robust routes including the shortest path. The SWR is applicable to large scale networks. We propose the multiple-sink version of the SWR that is namely MS-SWR, to be used in large scale ad hoc and sensor networks with multiple sinks. The MS-SWR can be used with multiple sinks without any functional and algorithmic modification in the SWR protocol. The performance of the SWR and the MS-SWR are evaluated by simulations. The performance of the system shows that the SWR satisfies the requirements of mobile ad hoc networks and outperforms the existing algorithms. The SWR is also tested against a hypothetic routing scheme that finds the shortest available path with no cost in order to compare the performance of the SWR against such an ideal case. Tests also indicate that MS-SWR is scalable for large scale networks.DoktoraPh

Secure Integrated Routing and Localization in Wireless Optical Sensor Networks

Wireless ad hoc and sensor networks are envisioned to be self-organizing and autonomous networks, that may be randomly deployed where no fixed infrastructure is either feasible or cost-effective. The successful commercialization of such networks depends on the feasible implementation of network services to support security-aware applications. Recently, free space optical (FSO) communication has emerged as a viable technology for broadband distributed wireless optical sensor network (WOSN) applications. The challenge of employing FSO include its susceptibility to adverse weather conditions and the line of sight requirement between two communicating nodes. In addition, it is necessary to consider security at the initial design phase of any network and routing protocol. This dissertation addresses the feasibility of randomly deployed WOSNs employing broad beam FSO with regard to the network layer, in which two important problems are specifically investigated. First, we address the parameter assignment problem which considers the relationship amongst the physical layer parameters of node density, transmission radius and beam divergence of the FSO signal in order to yield probabilistic guarantees on network connectivity. We analyze the node isolation property of WOSNs, and its relation to the connectivity of the network. Theoretical analysis and experimental investigation were conducted to assess the effects of hierarchical clustering as well as fading due to atmospheric turbulence on connectivity, thereby demonstrating the design choices necessary to make the random deployment of the WOSN feasible. Second, we propose a novel light-weight circuit-based, secure and integrated routing and localization paradigm within the WOSN, that leverages the resources of the base station. Our scheme exploits the hierarchical cluster-based organization of the network, and the directionality of links to deliver enhanced security performance including per hop and broadcast authentication, confidentiality, integrity and freshness of routing signals. We perform security and attack analysis and synthesis to characterize the protocol’s performance, compared to existing schemes, and demonstrate its superior performance for WOSNs. Through the investigation of this dissertation, we demonstrate the fundamental tradeoff between security and connectivity in WOSNs, and illustrate how the transmission radius may be used as a high sensitivity tuning parameter to balance there two metrics of network performance. We also present WOSNs as a field of study that opens up several directions for novel research, and encompasses problems such as connectivity analysis, secure routing and localization, intrusion detection, topology control, secure data aggregation and novel attack scenarios

Diseño de una ciudad inteligente para redes vehiculares

English: road safety has become a main issue for governments and car manufacturers in the last twenty years. The development of new vehicular technologies has favored companies, researchers and institutions to focus their efforts on improving road safety. During the last decades, the evolution of wireless technologies has allowed researchers to design communication systems where vehicles participate in the communication networks. Thus, the concept of Intelligent Transportation Systems (ITS) appeared. This concept is used when talking about communication technologies between vehicles and infrastructure that improve transport safety, its management, environmental performance, etc. Due to the high economic cost of real-life tests and experimentation, the use of simulators becomes really useful when developing ITS. Nonetheless, simulators not always include all the capabilities needed to simulate these kinds of networks. Thus, in this project the NCTUns simulator is modified in order to add new capabilities that allow users simulate ITS. Furthermore, smart city scenarios are simulated in order to evaluate how the use of these networks allows real-time statistic collection and calculation, and how modifications made in NCTUns work.Castellano: la seguridad en la carretera se ha convertido en un problema principal para gobiernos y fabricantes de automóviles en los últimos años. El desarrollo de nuevas tecnologías vehiculares ha permitido a compañías, investigadores e instituciones a centrar sus esfuerzos para mejorar la seguridad vial. Durante las últimas décadas, la evolución de la tecnología de comunicación inalámbrica ha permitido a investigadores el diseño de sistemas de comunicación en los cuales los vehículos forman parte de la red de comunicación. De esta forma, se creó el concepto de Sistema de Transporte Inteligente (STI), concepto utilizado al hablar sobre las tecnologías de comunicación entre vehículos e infraestructura, que mejoran la seguridad vial en el transporte, su mejor gestión, eficiencia medioambiental, etc. Debido al alto coste económico de probar STI en situaciones reales, el uso de simuladores es realmente útil a la hora de desarrollar este tipo de sistemas. Así, en este proyecto el simulador NCTUns ha sido modificado con el objetivo de añadir nuevas posibilidades al simulador que ayuden a diseñar STI. Además, un escenario de una ciudad inteligente ha sido simulado con el objetivo de evaluar como el uso de estas redes permite la recolección y el cálculo de estadísticas en tiempo real, además de comprobar cómo funcionan los cambios realizados en el simulador.Català: la seguretat a la carretera ha esdevingut un problema principal pels governs i pels fabricants d'automòbils en els últims anys. El desenvolupament de noves tecnologies de vehicles ha afavorit a les empreses, els investigadors i les institucions que centrin els seus esforços a millorar la seguretat viària. Durant les últimes dècades, l'evolució de les tecnologies sense fils ha permès als investigadors a dissenyar sistemes de comunicació on els vehicles poden participar en les xarxes de comunicació. D'aquesta manera, es crea el concepte de Sistema de Transport Intel·ligent (STI), concepte utilitzat en parlar sobre les tecnologies de comunicació entre vehicles i infraestructura que milloren la seguretat vial en el transport, la seva millor gestió, l'eficiència mediambiental, etc. A causa de l'alt cost econòmic de provar STI en situacions reals, l'ús de simuladors és realment útil a l'hora de desenvolupar STI. Així, en aquest projecte el simulador NCTUns ha estat modificat amb l'objectiu d'afegir noves possibilitats al simulador que ajudin a dissenyar STI a futurs usuaris. A més, un escenari d'una ciutat intel·ligent ha estat simulat amb l'objectiu d'avaluar com l'ús de la xarxa permet la recol·lecció i el càlcul d'estadístiques en temps real, a més de comprovar com funcionen els canvis realitzats en el simulador