Distributed fault tolerant topology control in wireless ad-hoc sensor networks

The development of practical, localization algorithms is probably the most needed and most challenging task in wireless ad-hoc sensor networks (WASNs). Localized algorithms are a special type of distributed algorithms where only a subset of nodes in the WASN participate in sensing, communication, and computation. We have developed a generic localized algorithm for solving optimization problems in wireless ad-hoc networks that has five components: (i) data acquisition mechanism, (ii) optimization mechanism, (iii) search expansion rules, (iv) bounding conditions and (v) termination rules. the main idea is to request and process data only locally and only from nodes who are likely to contribute to rapid formation of the final solution. The approach enables two types of optimization: The first, guarantees the fraction of nodes that are contacted while optimizing for solution quality. The second, provides guarantees on solution qualities while minimizing the number of nodes that are contacted and/or amount of communication. The localized optimization approach is applied to two fundamental problems in sensor networks: location discovery and exposure-based coverage. We demonstrate its effective-ness on a number of examples

Wireless ad-hoc sensor networks will provide one of the missing connections between the Internet and the physical world. One of the fundamental problems in sensor networks is the calculation of coverage. Exposure is directly related to coverage in that it is a measure of how well an object, moving on an arbitrary path, can be observed by the sensor network over a period of time.In addition to the informal definition, we formally define exposure and study its properties. We have developed an efficient and effective algorithm for exposure calculation in sensor networks, specifically for finding minimal exposure paths. The minimal exposure path provides valuable information about the worst case exposure-based coverage in sensor networks. The algorithm works for any given distribution of sensors, sensor and intensity models, and characteristics of the network. It provides an unbounded level of accuracy as a function of run time and storage. We provide an extensive collection of experimental results and study the scaling behavior of exposure and the proposed algorithm for its calculation.

We present a protocol that manages wireless ad-hoc sensor networks in several scenarios including large scale, high density and high mobility deployments. One of the main applications is to communicate important information from inaccessible areas by spreading just "enough" mobile sensors which must self-configure and assemble. According to our protocol, connectionless probabilistic (CoP) routing, the information is routed in a multi-hop, cluster level fashion by enabling each sensor to make individual decisions regarding its mode of operation. The aim is to prolong the network's lifetime by minimizing the energy spent for each communication. CoP is capable of addressing high mobility requirements as it is completely independent of any kind of topological knowledge and control messages. We show by extended experiments that CoP performs very well in terms of consumed energy by comparing it to a standard directed flooding and a greedy forwarding protocol.

A wireless ad hoc network is composed of several tiny and inexpensive device such as wireless sensor networks (WSNs) which have limited energy. In this network energy, efficiency is one of the most crucial requirements. Data transmitting in minimum power level is one way of maximizing energy efficiency. Thus, transmission power level of nodes should be managed in a smart way to improve energy efficiency. Topology control is one of the main algorithms used in a wireless network to decrease transmission power level while preserving network connectivity. Topology control could improve energy efficiency by reasonably tuning the transmission power level while preserving network connectivity in order to increase network capacity and lifetime. In pursuit of energy efficiency and connectivity, nodes can be selfish and are conflicting with each other. Therefore to overcome the conflict, game theory is used to construct energy efficient topology, as well as minimizing energy consumption. In this paper, the main goal and most recent energy efficient topology control algorithms in WSNs and ad hoc network are classified and studied according to their specific goals.

Wireless ad-hoc sensor networks have caught the fancy of many researchers through the world in a very small span of time. Although notable progress has been made in several key areas, several researchers falter in the way they look at sensor networks i.e. just another kind of wireless ad hoc networks, albeit one composed of energy constrained nodes. A key aspect that makes sensor networks different from traditional networks is their strong link to the physical world. We develop this perspective by studying an interesting class of sensor network applications called aggregation applications.We argue that when a user queries for aggregates like maximum, average etc., he is interested in knowing the statistics of the underlying physical process. In general, this is not equivalent to the statistics gathered from a bunch of nodes. We introduce a distinction between aggregates calculated over a region and aggregates calculated over a discrete set of nodes. We classify them as spatial and nodal aggregates respectively. Till now, researchers have followed the approach of doing nodal aggregation in response to every user query in sensor networks. For a continuous physical process and a random deployment of sensor nodes, which are a norm for sensor networks, the conventional approach of doing nodal aggregation produces inaccurate results.We verify our claim by studying a specific aggregation function namely the average over a region (spatial average) in detail. We use a voronoi-based approach to propose an algorithm for calculating spatial average in sensor networks. The algorithm can work in two modes -- centralized and distributed. The energy and accuracy tradeoff associated with each of the two modes is analyzed in detail. The efficacy of the proposed algorithm is tested over a wide variety of physical processes including real precipitation data of South America acquired over a span of past 50 years. We will show that our algorithm gives a 2-8 times performance gain as compared to the conventional approach of doing nodal aggregation. We further explore the robustness of our algorithm to link failures and channel impairments.Although not 100% accurate, our approach is a simple, efficient and a practical solution for calculating the spatial average. We have implemented our algorithm on Berkeley motes. Our first prototype implementation occupies less than 12K flash ROM and consumes less than 1.6K run-time memory. Our algorithm can be easily integrated with available frameworks for doing aggregation in sensor networks. For a minimal cost, our algorithm can be used to provide a spatial aggregation service on a network of motes.

In wireless, every device can moves anywhere without any infrastructure also the information can be maintained constantly for routing the traffic. The open issues of wireless Adhoc network the attacks which are chosen the forwarding attack that is dropped by malicious node to corrupt the network performance then the information integrity exposure. Aim of the problem that existing methods in Adhoc network for malicious node detection which cannot assure the traceability of the node as well as the fairness of node detection. In this paper, the proposed heterogeneous cluster based secure routing scheme provides trust based secure network for detection of attacks such as wormhole and black hole caused by malicious nodes presence in wireless Adhoc network. The simulation result shows that the proposed model is detect the malicious nodes effectively in wireless Adhoc networks. The malicious node detection efficiency can be achieved 96% also energy consumption also 10% better than existing method.

Wireless Ad hoc Sensor Networks (WASNs) are self organizing, self-configuring and multi-hop wireless networks, in which each node communicates with other nodes directly or indirectly through intermediate nodes without any infrastructure. Besides these characteristics challenges like limited energy, dynamic topology, low bandwidth and security exists. The arrangement of nodes in WASN is called topology which changes dynamically with respect to time and mobility. Energy conservation is a major challenge because of the limited battery resource. In order to conserve energy in the network layer many techniques were used. These techniques can be classified mainly into two categories. The first technique is making small number of nodes awake to transfer bulk amount of data and to maintain the network connectivity and making the remaining nodes to be in sleep mode to conserve energy. This technique is effective for low traffic conditions. In the second technique, topology in the network is controlled by power control technique. This technique is effective for high data traffic. To conserve energy in an efficient manner, a Dynamic Traffic Energy Efficient Topology (DTEET) dynamically adjusts network topology for various network traffic conditions in WASN either in low traffic or high traffic is proposed. And the proposed protocol DTEET is stimulated by using AODV as routing protocol using network simulator ns2.34 and compared with AODV and DSR [1,2]. The simulation results revealed that the proposed scheme performs well in terms of energy, delay, delivery ratio and mobility

Topology control algorithms in wireless Ad Hoc networks can be divided into two categories according to optimization goal, they are geometry structure and energy efficiency. The former constructs the network topology on the basis of geometry structure; the latter focuses on the energy efficiency of network. Based on abundant literature, this paper summarizes the recent situation of Ad Hoc network topology control field, introduces theories, properties and process of some typical topology control algorithms.

Connected dominated subsets (CDS) of nodes in wireless sensor network are always selected to form a virtual backbone. Construction of r-hop 2-connected dominating sets can reduce the size of CDS and the total amount of information to be transmitted. The 2-connected properties can provide higher fault tolerance and robustness as well. In this paper an approximation r-hop 2-connected dominating set algorithm for wireless sensor and ad-hoc networks is presented. The main strategy is partition to three phases: in the first phase, an r-hop independent dominating set is established; in the second phase, the r-hop dominating set is interconnected successively to form a connected subgraph; in the third phase, more vertices are selected and added into dominating set to make it 2-connected. Extensive simulations according to the algorithm steps have been conducted. Performance with detailed analysis has been shown at last.

Energy is vital parameter for wireless ad hoc sensor network. Particularly it has more powerful requirement under dynamic environment. Clustering has made present wireless sensor network system energy aware due to data aggregation, data fusion and data compression at cluster heads. That results non redundant message generation and transmission, leads to minimum radio overhead. But, under fully dynamic network condition the result is not much satisfactory in Wireless Ad hoc Sensor Networks (WASNs). In this paper, an analytical approach has been presented to understand energy complexity of the network under highly dynamic, random and realistic mobile network environment of the sensor nodes in Cluster based WASN. It can help to design a novel energy efficient cluster routing protocol for wireless ad hoc sensor networks with mobility.

The emergence of wireless ad-hoc networks is considered extremely attractive in terms of new applications' enabler. The integration of reliable sensors in nodes of wireless ad-hoc networks has posed various interesting challenges to the community of researchers and engineers. We focus in this paper on two fundamental issues: supporting high mobility of sensors and guaranteeing continuity of sensing, while providing for the correlation of collected data. We propose an efficient scheme for the management of data, sensor mobility, and sensing security

The paper proposes a new clustering approach based on genetic algorithms (GA) and devoted to improving energy efficiency in ad-hoc wireless sensor networks (WSN). A special designed MATLAB framework operates as test bench to evaluate different implementations. The solutions of the optimization algorithms provide the number of clusters along with the cluster structures. Real-time implementations of such algorithms justify the necessity to minimize their execution time. We have devised custom genetic operators in order to improve the GA convergence. The process of fine tuning of the GA parameters proved to be also extremely important. Intensive simulation studies have confirmed the validity and efficiency of the proposed solutions. Using our approach, we have improved the speed of convergence for the GA up to 50%, as compared with existing approaches, while reducing considerably the minimum communication distance in the ad-hoc WSN.

Coverage is a typical problem in wireless sensor networks to fulfil the issued sensing tasks. In general, sensing coverage represents how well an area is monitored by sensors. The quality of a sensor network can be reflected by the levels of coverage and connectivity that it offers. The coverage problem has been studied extensively, especially when combined with connectivity and energy efficiency. Constructing a connected fully covered, and energy efficient sensor network is valuable for real world applications due to the limited resources of sensor nodes. In this paper, we survey recent contributions addressing energyefficient coverage problems in the context of static WASNs, networks in which sensor nodes do not move once they are deployed and present in some detail of the algorithms, assumptions, and results. A comprehensive comparison among these approaches is given from the perspective of design objectives, assumptions, algorithm attributes and related results.

The sensor networks are characterized by tiny, inexpensive, and advanced communication technology. However, wireless ad-hoc sensor networks (WASNs) have some issues such as the limited amount of energy, multipath fading, and some other issues when they applied in disaster situations. For reducing power consumption, we show mathematical analysis of energy saving, and enhanced error symbol probability. The simulation results prove our analysis. As for the multipath fading, we also show the mathematical analysis of fading channel characteristics and channel model, as well as how to mitigate the multipath fading by modulation and diversity techniques. From the simulation results, we prove the proposed system with amplify-and-forward (AF) relaying can achieve a 2.5 dB performance gain the BER 10-4 whereas the achievable improvement is almost a 4 dB at the BER 10-5 when using maximal ratio combining.

It is our great pleasure to welcome you to the 3rd ACM Workshop on Security of Ad Hoc and Sensor Networks (SASN'05), held in conjunction with the 12th ACM Conference on Computer and Communications Security (CCS'05), November 7, 2005, in Alexandria, Virginia.This year we received a total of 39 submissions on various aspects of ad-hoc and sensor network security. The program committee selected 6 as regular papers that cover a variety of topics, including trust establishment in Mobile Ad-Hoc Networks (MANETs), security of vehicular ad-hoc networks, secure group communication, key pre-distribution for sensor networks, jamming attacks against sensor network MAC protocols, and defense against Denial-of-Service (DoS) attacks. This year we continue the tradition of SASN'03 and SASN'04 to encourage the presentation and discussion of work-in-progress on ad-hoc and sensor network security. Among the 39 submissions, the program committee selected 7 papers to present in work-in-progress sessions, covering topics on anonymous routing for MANETs, key distribution for inter-group multicast in ad-hoc networks, improved topology assumptions for threshold cryptography in MANETs, RFID security, tracing in mobile wireless sensor networks, time synchronization attacks in sensor networks, and coordinated deployment for improving secure communications and sensing coverage in wireless sensor networks. In addition, the program includes a panel on Advances in Sensor and Ad-hoc Network Security and an invited keynote talk by Radha Poovandran (University of Washington) on Information Assurance in MANETs and Wireless Sensor Networks. We hope that these proceedings will serve as a valuable reference for security researchers and developers.