Dynamic Event Coverage in Hybrid Wireless Sensor Networks

Wireless Sensor Networks (WSNs) is composed of sinks and sensor nodes, which can monitor large-scale environment. The sensor nodes have several advantages, such as low cost, small size, and capability of mobility, and they can do data sensing, data processing and wireless communication. However, the greatest challenge is the constraints of energy. The most critical issue is how to minimize the energy consumption and keep tracking the mobile target in WSNs. In this paper, we propose a tracking approach for tracking mobile target in hybrid wireless sensor network which consisting of static and mobile node. While static nodes are random distributed in the Field of Interested (FoI) and mobile nodes are moved to fill the coverage hole. We predict the area where the target may cross and construction the local barrier coverage to detect the target. In order to reduce the energy consumption, we wakeup the portion of constructed local barrier coverage to tracking the target. The simulation shows the proposed scheme can reduce the energy consumption and missing rate.

Success of Wireless Sensor Networks largely depends whether the deployed network can provide desired coverage with acceptable network lifetime. This paper proposes a distributed protocol for ensuring area coverage using a combination of mobile and static sensor nodes. Most of the assumptions made in our approach are realistic (sensing model, movement thresholds based on real radio characteristics etc.) and implementable in real-life applications. We demonstrate that, for different type of initial deployments, our proposed movement algorithms consume only 30-40% of the energy consumed by the basic virtual force algorithm. We formulated our problem as Integer Linear Program to arrive at idealistic optimal solutions that form basis of our performance comparison. We validated our results through extensive discrete event simulations.

In large scale Wireless Sensor Networks (WSNs), the random deployment of the sensor nodes does not guarantee the desired level of the area coverage especially when the network is sparse. One of the solutions to overcome this problem is to use a mobile robot that is equipped with, in addition to the sensing unit, an actuator unit that controls its movement. In this case, the mobile robot is considered as a mobile sensor node that has the capability to monitor the uncovered regions in the sensor field. However, the main challenge in this case is how to control the movement of the mobile robot such that the area coverage is maximized and the time required to sample the uncovered regions is minimized. In this paper, we propose a fuzzy logic-based approach that controls the mobile robot movement in the sensor field in order to maximize the area coverage. The inputs of the fuzzy system determine the next point that the mobile node will select when it moves in the sensor field. Simulation results have shown that the proposed approach outperforms the random and standard moving patterns.

Random Geometric Graphs have been a very influential and well-studied model of large networks, such as sensor networks, where the network nodes are represented by the vertices of the RGG, and the direct connectivity between nodes is represented by the edges. This assumes homogeneous wireless nodes with uniform transmission ranges. In real life, there exist heterogeneous wireless networks in which devices have dramatically different capabilities. The connectivity of a WSN is related to the positions of nodes, and those positions are heavily affected by the method of sensor deployment. As sensors may be spread in an arbitrary manner, one of the fundamental issues in a wireless sensor network is the coverage problem. In this paper, I study connectivity and coverage in hybrid WSN based on dynamic random geometric graph.

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.

When detecting a target or monitoring a physical phenomenon in a region, the deployment problem is fundamental in these applications. Traditionally, stationary sensor networks are deployed to carry out the sensing operations. It is well known that the mobility of sensor nodes can improve the coverage and the probability of the detecting, so we deal with the problem of detecting a target using hybrid sensor networks which contain both stationary sensors and mobile sensors. In this paper, to begin with, we prove that the node deployment problem is NP-complete. Then, one polynomial algorithm for node deployment in hybrid wireless sensor networks is proposed, which aims at minimizing the number of all sensors to reduce the cost. The simulations verify the efficiency of our algorithm.

A Hybrid Wireless Sensor network (HWSN) with static and mobile nodes is considered. Static sensors monitor the environment and report events occurring in the sensing field. Mobile sensors are then dispatched to visit these event locations to conduct more advanced analysis. Mobile sensor will collect the information about the event and in turn will send it to the base station. As WSN is vulnerable to attacks, a big challenge is to provide security for the communication that takes place between the base station and mobile sensor. Therefore the goal of the paper is to provide security for the data that is transferred between the base station and mobile sensor. In this paper data security will be provided using Sensor Network Encryption Protocol (SNEP) which is one of the building block of SPINS. This paper contributes in defining a suitable data security mechanism.

Toward the end of the 20th century, the Internet has been able to provide a large number of users with the ability to move diverse forms of information readily and thus has revolutionized business, industry, defense, science, education, research, and human interactions. In the last 10 years, sensor networking combines the technology of modern microelectronic sensors, embedded computational processing systems, and modern computer networking methodology. It is believed that sensor networking in the 21st century will be equally significant by providing measurement of the spatial-temporal physical phenomena around us, leading to a better understanding and utilization of this information in a wide range of applications. Sensor networking will be able to bring a finer-grained and fuller measurement and characterization of the world around us to be processed and communicated, so the decision makers can utilize the information to take actions in near-real-time. The potential applications enabled by SNs include security and surveillance, environmental monitoring and control, target detection and tracking, etc. Wireless sensor networks utilize the extensive networking concepts of ad hoc networks and apply them to specific sensor network scenarios. This mini-special issue comprises three papers covering three quiet diverse aspects of wireless sensor networks. The first paper, “Lifetime Maximization Based on Coverage and Connectivity in Wireless Sensor Networks,” is by T. Zhao et al. They studied the problem of network lifetime maximization for QoS specific information retrieval for the reconstruction of a spatially correlated signal field in a wireless sensor network for two wireless transmission cases. In one case, they assumed there exist single-hop transmissions between sensors and the access point, and in the other case, the measurements are sent to the access point through multi-hop transmissions. To address both of these problems, they formulated the problems using integer programming based on the theories of coverage and connectivity in sensor networks and then derived upper bounds for the network lifetime that provides benchmarks for the performance of suboptimal methods. Several lowcomplexity suboptimal algorithms for joint node scheduling and data routing were then proposed to approach the performance upper bounds. The second paper, “Using Heterogeneity to Enhance Random Walk-based Queries,” is by M. Zuniga et al. They presented a study of the impact of heterogeneous node connectivity on random walk-based queries. The main contribution of the work is showing that with a small percentage (e.g., 10%) of high-degree nodes in the network and using a simple distributed push-pull mechanism, significant cost savings can be obtained (e.g., between 30% and 70%) depending on the coverage of the high-degree nodes. Their work provides interesting theoretical results for line topologies showing that when cluster-heads have a coverage of k nodes to the right and left and are uniformly distributed, a fraction of 4/5k J Sign Process Syst (2009) 57:381–383 DOI 10.1007/s11265-009-0377-9

Coverage in wireless sensor networks is a critical issue since it reflects the cost and detection capability of the network. Sensor coverage model is closely to the sensing functions of different types of sensors while network coverage is a collaborative measure from geographically distributed sensors. The coverage problems in wireless sensor networks have been formulated in various ways with different assumptions, constraints and objectives. In this work, a collaborative coverage model is proposed in the target surveillance application, while sensor sensing probabilistic model is introduced. Furthermore, a collaborative target coverage optimization algorithm (CTCOMSN) is presented to prolong the network lifetime in energy constraint mobile sensor networks. Simulation results show that CTCOMSN can prolong the lifetime greatly while improving the sensing quality.

Aiming at the uneven random coverage distribution of wireless sensor networks sensor nodes, the sparrow search algorithm (SSA) is used to optimize the node coverage of wireless sensor networks. To improve the global search capability of SSA, the algorithm is improved and applied to the wireless sensor networks of bridge monitoring. For enhancing the coverage of the wireless sensor networks, this article uses two improved methods. One is to use the good point set theory to make the initial population evenly distributed; another is to introduce a weight factor to speed up its convergence. The experiments have proved the reliability and rationality of the algorithm. The improved algorithm is superior to other meta-heuristic algorithms and provides a new idea for optimizing bridge monitoring wireless sensor networks coverage.

Wireless sensor networks (WSNs) use sensors to monitor phenomena such as temperature, humidity, groundwater levels and transmit this information to a base station using wireless channels. WSNs find applications in military, ecological, and health-related areas. A hybrid wireless sensor network includes two networks: an ad hoc wireless network and a wireless sensor network. The nodes in the ad hoc network act as base stations conducting surveillance on the WSN. In this dissertation, we focus on the key management issues in hybrid wireless sensor networks. The key management issues in hybrid wireless sensor networks can be divided into three categories according to which layer they affect: ad hoc network layer, wireless sensor network layer, and integrated cross layer. At the ad hoc network layer, we propose two elliptic curve discrete logarithm problem (ECDLP) based schemes for secure group communication (SGC). Unlike the vast majority of secure group communication protocols using the discrete logarithm problem (DLP) based Diffie-Hellman as the basic key agreement protocol, our solutions use the ECDLP-based Diffie-Hellman protocol. We also extend our research on secure group communication to the wireless sensor network layer. We formally define the grouping and secure group communication problems in WSNs. We further propose and evaluate four centralized group rekeying (CGK) schemes for SGC in WSNs. Our proposed key management protocol at the integrated cross layer, mKeying, includes two schemes, a key distribution scheme, KeyDist, supporting multiple base stations in the network, and a centralized key revocation scheme, KeyRev, for removing compromised sensor nodes from the sensor network. Through these protocols for key distribution, key revocation, and group communication, we present an integrated approach to provide security in hybrid wireless sensor networks.

The wireless sensor network composes of sensors with limited battery power. And, consequently, to save sensor's energy effectively so as to extend the lifetime of the sensor network is one of important issues for the network deployment. In this article, we assume that limited sense nodes are equipped with high power and moving capabilities in the cluster based sensor network. The main objective of these high power nodes is to support the cluster header, which is going to exhaust its power, for data forwarding. The power consumption required for the movement is much larger than that of data forwarding. If the mobile node moves frequently, it will exhaust its power shortly. In this paper, a novel approach is proposed to effectively guide the movement of the high power nodes by considering the above issues. The simulation results show that the proposed approach can balance the sensor energy and extend the network lifetime when compared to the LEACH-C scheme for the same network environment.

In hybrid wireless sensor networks composed of both static and mobile sensor nodes, the random deployment of stationary nodes may cause coverage holes in the sensing field. Hence, mobile sensor nodes are added after the initial deployment to overcome the coverage holes problem. To achieve optimal coverage, an efficient algorithm should be employed to find the best positions of the additional mobile nodes. This paper presents a genetic algorithm that searches for an optimal or near optimal solution to the coverage holes problem. The proposed algorithm determines the minimum number and the best locations of the mobile nodes that need to be added after the initial deployment of the stationary nodes. The performance of the genetic algorithm was evaluated using several metrics, and the simulation results demonstrated that the proposed algorithm can optimize the network coverage in terms of the overall coverage ratio and the number of additional mobile nodes.

Unknown target search, in an unknown environment, is a complex problem in Wireless Sensor Network (WSN). It does not have a linear solution when target’s location and searching space is unknown. For the past few years, many researchers have invented novel techniques for finding a target using either Static Sensor Node (SSN) or Mobile Sensor Node (MSN) in WSN i.e. Hybrid WSN. But there is a lack of research to find a solution using hybrid WSN. In the current research, the problem has been addressed mostly using non-biological techniques. Due to its complexity and having a non-linear solution, Bio-inspired techniques are most suited to solve the problem. This paper proposes a solution for searching of randomly moving target in unknown area using only Mobile sensor nodes and combination of both Static and Mobile sensor nodes. In proposed technique coverage area is determined and compared. To perform the work, novel algorithms like MSNs Movement Prediction Algorithm (MMPA), Leader Selection Algorithm (LSA), Leader’s Movement Prediction Algorithm (LMPA) and follower algorithm are implemented. Simulation results validate the effectiveness of proposed work. Through the result, it is shown that proposed hybrid WSN approach with less number of sensor nodes (combination of Static and Mobile sensor nodes) finds target faster than only MSN approach.

An exact approach for maximizing the lifetime of sensor networks with adjustable sensing ranges