Developing Energy Aware Distributed Aggregation Tree Technique for Wireless Sensor Networks

Wireless sensor network WSN consists of small sensor nodes with limited resources, which are sensing, gathering and transmitting data to base station. Sensors of various types are deployed ubiquitously and widely in varied environments for instance, wildlife reserves, battlefields, mobile networks and office building. Sensor nodes are having restricted and non replenishable power resources and this is regarded as one of the main of their critical limits. All applied techniques and protocols on sensor nodes must take into consideration their power limitation. Data aggregation techniques are used by sensor nodes in order to minimize the power consumption by organizing the communication among sensor nodes and eliminating the redundant of sensed data. This paper proposed lightweight modification on data aggregation technique named Energy Aware Distributed Aggregation Tree EADAT. The main principle of this development is using the available information in sensor nodes to pass the role of parent node among sensor nodes in each cluster. The process of passing parent node role is based on nominating the sensor nodes which have higher power on regular bases. A model based on tree network architecture is designed for validation purpose and is used with NS2 simulator to test the proposed development. EADAT and EADAT with proposed development are applied on the designed model and the results were promisin

Integrated placement and routing of relay nodes for fault-tolerant hierarchical sensor networks

In two-tiered sensor networks, using higher-powered relay nodes as cluster heads has been shown to lead to further improvements in network performance. Placement of such relay nodes focuses on achieving specified coverage and connectivity requirements with as few relay nodes as possible. Existing placement strategies typically are unaware of energy dissipation due to routing and are not capable of optimizing the routing scheme and placement concurrently. We, in this thesis, propose an integrated integer linear program (ILP) formulation that determines the minimum number of relay nodes, along with their locations and a suitable communication strategy such that the network has a guaranteed lifetime as well as ensuring the pre-specified level of coverage (ks) and connectivity (kr). We also present an intersection based approach for creating the initial set of potential relay node positions, which are used by our ILP, and evaluate its performance under different conditions. Experimental results on networks with hundreds of sensor nodes show that our approach leads to significant improvement over existing energy-unaware placement schemes

EFFICIENT CAMERA SELECTION FOR MAXIMIZED TARGET COVERAGE IN UNDERWATER ACOUSTIC SENSOR NETWORKS

In Underwater Acoustic Sensor Networks (UWASNs), cameras have recently been deployed for enhanced monitoring. However, their use has faced several obstacles. Since video capturing and processing consume significant amounts of camera battery power, they are kept in sleep mode and activated only when ultrasonic sensors detect a target. The present study proposes a camera relocation structure in UWASNs to maximize the coverage of detected targets with the least possible vertical camera movement. This approach determines the coverage of each acoustic sensor in advance by getting the most applicable cameras in terms of orientation and frustum of camera in 3-D that are covered by such sensors. Whenever a target is exposed, this information is then used and shared with other sensors that detected the same target. Compared to a flooding-based approach, experiment results indicate that this proposed solution can quickly capture the detected targets with the least camera movement

Controlled Mobility in Mobile Sensor Networks: Advantages, Issues and Challenges

International audienceRecently, wireless self-organizing networks are attracting a lot of interest in the research community. Moreover, in the last decade many mobile devices have appeared in the market. Exploiting mobility in a wireless environment, instead of considering it as a kind of disturbance, is a fundamental concept that the research community is beginning to appreciate now. Of course, the advantages obtainable through the use of the mobility imply the knowledge of the different types of mobility and the way to include it in the management architecture of the wireless networks. In this work we claim that mobility and wireless sensor networks can be considered as two synergetic elements of the same reality. For this purpose, we sketch a macro-classification of the different objectives which can be pursued by controlled mobility. Moreover, we identify and highlight the interactions between this specific type of mobility and the layers of the control stack. Lastly, this paper reports a case study in which we show how controlled mobility can be exploited practically

Survey on the state of the art of wireless sensor networks

Este artículo presenta un estudio del estado del arte de las redes de sensores inalámbricas, las cuales siguen un desarrollo creciente y presentan una gran variedad de aplicaciones. Estas redes constituyen un campo actual y emergente de estudio donde se combina el desarrollo de computadores, comunicaciones inalámbricas y dispositivos móviles e integración con otras disciplinas como agricultura, biología, medicina, etc. Se presenta el concepto principal, los componentes, topologías, estándares, aplicaciones, problemas y desafíos, luego se profundiza en soluciones de seguridad y se concluye con herramientas básicas de simulación.This article presents a survey of the state of the art of wireless sensor networks, which follows a growing development and a wide variety of applications. These networks provide a current and emerging field of study where combines the development of computers, wireless communications and mobile devices and integration with other disciplines such as agriculture, biology, medicine, etc. Presents the main concept, components, topologies, standards,  applications,  problems  and  challenges,  deepens  security  solutions  and conclude with basic tools of simulation

Managing malicious transactions in mobile database systems

Title from PDF of title page, viewed on March 15, 2013Thesis advisor: Vijay KumarVitaIncludes bibliographic references (p. 53-55)Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2012Database security is one of the most important issues for any organization, especially for financial institutions such as banks. Protecting database from external threats is relatively easier and a number of effective security schemes are available to organizations. Unfortunately, this is not so in the case of threats from insiders. Existing security schemes for such threats are some variation of external schemes that are not able to provide desirable security level. As a result, still authorized users (insiders) manage to misuse their privileges for fulfilling their malicious intent. It is a fact that most external security breaches succeed mainly with the help of insiders. An example for an insider is the Enron scandal of 2001 which led to bankruptcy of Enron Corporation. The firm was widely regarded as one of the most innovative, fastest growing and best managed business in the United States. When Enron filed for bankruptcy its share prices fall from US$90 to$1 causing a loss of nearly $11 billion dollar to its stakeholders. Financial officers and executives misled outside investors, auditors and Enron's board of directors about corporation's net income and liabilities. These insiders kept reported income and reported cash flow up, asset value inflated and liabilities off the book to meet Wall Street expectations. Enron's$63.4 billion in assets made it the largest corporate bankruptcy in American history at that time. Existing security policies are inadequate to prevent the attacks from insiders. Current database protections mechanisms do not fully protect occurrence of these malicious transactions. These requires human intervention in some form or other to detect malicious transactions. In a database, a transaction can affect the execution of the subsequesnt transactions thereby spreading the damage and hence making the attack recovery more complex. The problem of malicious attack becomes more pronounced when we are dealing with mobile database systems. This thesis proposes a solution to mitigate insider attack by identifying such malicious transactions. It develops a formal framework for characterizing mobile transaction by identifying essential components like order of data access, order of operations and user profile.Introduction -- Mobile database system -- Research problem -- Solution and scheme -- Simulation and results -- Future work -- Conclusio

On backoff mechanisms for wireless Mobile Ad Hoc Networks

Since their emergence within the past decade, which has seen wireless networks being adapted to enable mobility, wireless networks have become increasingly popular in the world of computer research. A Mobile Ad hoc Network (MANET) is a collection of mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure. MANETs have received significant attention in recent years due to their easiness to setup and to their potential applications in many domains. Such networks can be useful in situations where there is not enough time or resource to configure a wired network. Ad hoc networks are also used in military operations where the units are randomly mobile and a central unit cannot be used for synchronization. The shared media used by wireless networks, grant exclusive rights for a node to transmit a packet. Access to this media is controlled by the Media Access Control (MAC) protocol. The Backoff mechanism is a basic part of a MAC protocol. Since only one transmitting node uses the channel at any given time, the MAC protocol must suspend other nodes while the media is busy. In order to decide the length of node suspension, a backoff mechanism is installed in the MAC protocol. The choice of backoff mechanism should consider generating backoff timers which allow adequate time for current transmissions to finish and, at the same time, avoid unneeded idle time that leads to redundant delay in the network. Moreover, the backoff mechanism used should decide the suitable action to be taken in case of repeated failures of a node to attain the media. Further, the mechanism decides the action needed after a successful transmission since this action affects the next time backoff is needed. The Binary exponential Backoff (BEB) is the backoff mechanisms that MANETs have adopted from Ethernet. Similar to Ethernet, MANETs use a shared media. Therefore, the standard MAC protocol used for MANETs uses the standard BEB backoff algorithms. The first part of this work, presented as Chapter 3 of this thesis, studies the effects of changing the backoff behaviour upon a transmission failure or after a successful transmission. The investigation has revealed that using different behaviours directly affects both network throughput and average packet delay. This result indicates that BEB is not the optimal backoff mechanism for MANETs. Up until this research started, no research activity has focused on studying the major parameters of MANETs. These parameters are the speed at which nodes travel inside the network area, the number of nodes in the network and the data size generated per second. These are referred to as mobility speed, network size and traffic load respectively. The investigation has reported that changes made to these parameters values have a major effect on network performance. Existing research on backoff algorithms for MANETs mainly focuses on using external information, as opposed to information available from within the node, to decide the length of backoff timers. Such information includes network traffic load, transmission failures of other nodes and the total number of nodes in the network. In a mobile network, acquiring such information is not feasible at all times. To address this point, the second part of this thesis proposes new backoff algorithms to use with MANETs. These algorithms use internal information only to make their decisions. This part has revealed that it is possible to achieve higher network throughput and less average packet delay under different values of the parameters mentioned above without the use of any external information. This work proposes two new backoff algorithms. The Optimistic Linear-Exponential Backoff, (OLEB), and the Pessimistic Linear-Exponential Backoff (PLEB). In OLEB, the exponential backoff is combined with linear increment behaviour in order to reduce redundant long backoff times, during which the media is available and the node is still on backoff status, by implementing less dramatic increments in the early backoff stages. PLEB is also a combination of exponential and linear increment behaviours. However, the order in which linear and exponential behaviours are used is the reverse of that in OLEB. The two algorithms have been compared with existing work. Results of this research report that PLEB achieves higher network throughput for large numbers of nodes (e.g. 50 nodes and over). Moreover, PLEB achieves higher network throughput with low mobility speed. As for average packet delay, PLEB significantly improves average packet delay for large network sizes especially when combined with high traffic rate and mobility speed. On the other hand, the measurements of network throughput have revealed that for small networks of 10 nodes, OLEB has higher throughput than existing work at high traffic rates. For a medium network size of 50 nodes, OLEB also achieves higher throughput. Finally, at a large network size of 100 nodes, OLEB reaches higher throughput at low mobility speed. Moreover, OLEB produces lower average packet delay than the existing algorithms at low mobility speed for a network size of 50 nodes. Finally, this work has studied the effect of choosing the behaviour changing point between linear and exponential increments in OLEB and PLEB. Results have shown that increasing the number of times in which the linear increment is used increases network throughput. Moreover, using larger linear increments increase network throughput

On the performance of probabilistic flooding in wireless mobile ad hoc networks

Broadcasting in MANET’s has traditionally been based on flooding, but this can induce broadcast storms that severely degrade network performance due to redundant retransmission, collision and contention. Probabilistic flooding, where a node rebroadcasts a newly arrived one-to-all packet with some probability, p, was an early suggestion to reduce the broadcast storm problem. The first part of this thesis investigates the effects on the performance of probabilistic flooding of a number of important MANET parameters, including node speed, traffic load and node density. It transpires that these parameters have a critical impact both on reachability and on the number of so-called “saved rebroadcast packets” achieved. For instance, across a range of rebroadcast probability values, as network density increases from 25 to 100 nodes, reachability achieved by probabilistic flooding increases from 85% to 100%. Moreover, as node speed increases from 2 to 20 m/sec, reachability increases from 90% to 100%. The second part of this thesis proposes two new probabilistic algorithms that dynamically adjust the rebroadcasting probability contingent on node distribution using only one-hop neighbourhood information, without requiring any assistance of distance measurements or location-determination devices. The performance of the new algorithm is assessed and compared to blind flooding as well as the fixed probabilistic approach. It is demonstrated that the new algorithms have superior performance characteristics in terms of both reachability and saved rebroadcasts. For instance, the suggested algorithms can improve saved rebroadcasts by up to 70% and 47% compared to blind and fixed probabilistic flooding, respectively, even under conditions of high node mobility and high network density without degrading reachability. The final part of the thesis assesses the impact of probabilistic flooding on the performance of routing protocols in MANETs. Our performance results indicate that using our new probabilistic flooding algorithms during route discovery enables AODV to achieve a higher delivery ratio of data packets while keeping a lower routing overhead compared to using blind and fixed probabilistic flooding. For instance, the packet delivery ratio using our algorithm is improved by up to 19% and 12% compared to using blind and fixed probabilistic flooding, respectively. This performance advantage is achieved with a routing overhead that is lower by up to 28% and 19% than in fixed probabilistic and blind flooding, respectively