Wenping Chen

Minimum camera barrier coverage in wireless camera sensor networks

Barrier coverage is an important issue in wireless sensor network. In wireless camera sensor networks, the cameras take the images or videos of target objects, the position and angle of camera sensor impact on the sense range. Therefore, the barrier coverage problem in camera sensor network is different from scalar sensor network. In this paper, based on the definition of full-view coverage, we focus on the Minimum Camera Barrier Coverage Problem (MCBCP) in wireless camera sensor networks in which the camera sensors are deployed randomly in a target field. Firstly, we partition the target field into disjoint subregions which are full-view-covered regions or not-full-view-covered regions. Then we model the full-view-covered regions and their relationship as a weighted directed graph. Based on the graph, we propose an algorithm to find a feasible solution for the MCBCP problem. We also proved the correctness of the solution for the MCBCP problem. Furthermore, we propose an optimal algorithm for the MCBCP problem. Finally, simulation results demonstrate that our algorithm outperforms the existing algorithm.

Minimum energy cost k-barrier coverage in wireless sensor networks

Barrier coverage problem is one of important issues in wireless sensor networks. In this paper we study the minimum energy cost k-barrier coverage problem in wireless sensor network in which each sensor has l + 1 sensing power levels. First, we transform the minimum energy cost k-barrier coverage problem into a minimum cost flow problem with side constraints. Then we use Lagrangian relaxation technique to solve this minimum cost flow problem. Moreover, we propose two efficient heuristics for the minimum energy cost k-barrier coverage problem. Simulations evaluate that our algorithms are efficient.

VAN: Vehicle-assisted shortest-time path navigation

Traffic congestion is a very serious problem in large cities. With the number of vehicles increasing rapidly, especially in cities whose economy is booming, the situation is getting even worse. In this paper, by leveraging the techniques of Vehicular Ad hoc Networks (VANETs) we present a dynamic navigation protocol called VAN for individual vehicles to find the shortest-time paths toward their given destinations. Specifically, a vehicle initiates a number of queries, which are routed by VANETs along different paths toward its destination. During query forwarding, the real-time road traffic information in each road segment is aggregated from multiple participating vehicles and returned to the source after the query reaches the destination. This information enables the source to calculate the shortest-time path. We also propose two forwarding optimization methods to reduce communication costs and an error handling mechanism to deal with abnormal circumstances. To evaluate its performance, we use the real traffic data of Beijing, including 2,308 road segments at two different times. Our simulation results demonstrate that our protocol, on average, could save around 30% driving time, compared to traveling along the shortest distance paths.

Minimum cost collaborative sensing network with mobile phones

Mobile phones with a rich set of embedded sensors have been applied in various collaborative sensing applications. In some applications, to encourage mobile phone users performing collaborative sensing tasks, the data demanders may pay mobile phone users. However, none of the existing works takes into account it. In this paper, we study the Minimum Cost of Attaining the Required Data with mobile phones (MCARD) problem in collaborative sensing network. Given sensing regions R = {R1, R2, ..., Rm}, the set of requisite data Di for each sensing region Ri and a set of mobile phones M, the MCARD problem is how to select mobile phones to get all the required data such that the total cost on paying mobile phone users is minimized. We first formally define the MCARD problem. Then, we propose an approximation algorithm for the MCARD problem with the determinate trajectories of mobile phones and a heuristic algorithm for that trajectories are unknown respectively. Simulation results demonstrate our algorithms are efficient.

Energy efficient k-barrier coverage in limited mobile wireless sensor networks

Energy cost and reliability are two main concerns in barrier coverage for wireless sensor networks. In this paper, we take the energy cost and reliability as objectives respectively to study two problems of k-barrier coverage: the minimum energy cost k-barrier coverage problem in static wireless sensor networks and the maximum k-barrier coverage problem in limited mobile wireless sensor networks. For the minimum energy cost k-barrier coverage problem, all sensors are stationary, and each sensor has l+1 sensing power levels in the network, the objective of the problem is to find a sensing level assignment to form k-barrier coverage such that the total power consumed by the k-barrier is minimized. We firstly transform it into a minimum cost flow problem with side constraints and use Lagrangian relaxation technique to solve the minimum cost flow problem. Then, we also propose a heuristic algorithm. For the maximum k-barrier coverage problem, each sensor can move within the limited range, the objective of the problem is to form more barriers while some sensors can move within limited range. We formulate the problem into an integer linear programming (ILP), then propose two heuristic algorithms based on the linear programming (LP) relaxation. The simulation results demonstrate our algorithms are efficient.

Efficient algorithm for maximum lifetime many-to-one data aggregation in wireless sensor networks

Data aggregation problem with maximising network lifetime is one of important issues in wireless sensor networks. In this paper, we study the maximum lifetime many-to-one data gathering with aggregation (MLMTODA) problem: given locations of sensors and a base station together with available energy of each sensor, and a set of sources, find a schedule in which data should be gathered from all the sources and transmitted to the base station, such that the lifetime of the network is maximised. We propose efficient algorithms to solve the MLMTODA problem. Our simulations demonstrate that the proposed algorithm has a good performance for the MLMTODA problem.

Sweep-Coverage with Energy-Restricted Mobile Wireless Sensor Nodes

Most of the existing results in sweep-coverage focused on minimizing the number of the mobile sensor nodes by carefully planning their corresponding trajectories such that each target of interest can be periodically monitored (within every t time unit). However, the starting locations of the mobile sensors, at which the service depots (or equivalently base stations) of the nodes are usually located, are never considered in the trajectory planning. In order to provide sweep-coverage for a long period of time, each node also needs to periodically visit a base station to replace a battery or refueled (within every T time unit). Motivated by this observation, this paper introduces two new sweep-coverage problems, in which each mobile sensor node is required to visit a base station periodically, namely (t,T)-SCOPe-1 and (t,T)-SCOPe-M, each of which considers one single base station and M base stations for all of the nodes, respectively. We prove those problems are NP-hard and propose heuristic algorithms for them. In addition, we conduct simulations to evaluate the average performance of the proposed algorithms and study their average behavior characteristics.

Energy-efficient algorithm for the target Q-coverage problem in wireless sensor networks

In this paper we study the target Q-coverage (TQC) problem where each target needs to be covered by different numbers of sensors. We try to find a collection of Q-covsets which satisfy the coverage quality requirement to maximize the network lifetime. We first prove that the problem is NP-Hard. Then we design a greedy algorithm to efficiently compute the Q-covsets. Finally, simulation results are presented to verify our approach.

Conflict-Free Many-to-One Data Aggregation Scheduling in Multi-Channel Multi-Hop Wireless Sensor Networks

In this paper, we studied the minimum latency conflict-free many-to-one data aggregation scheduling problem in multi-channel multi-hop wireless sensor networks: Given locations of all sensors and a base station, some sensors which are called as sources, find a schedule such that data from all sources can be transmitted to the base station without any conflict and the latency is minimized. In this model, each sensor has three parameters which are transmission range r, interference range ¿r and carrier sensing range ¿Ar where ¿, and ¿A are constant. There are ¿E . 1 available channels for communications. We designed an approximation algorithm with ratio ( a ¿E +11 b ¿E). This work improves our previous work [9] when ¿E = 1. Extensive simulations evaluate the performance of the algorithm. Index Terms.conflict-free data aggregation, latency, multichannel, approximation algorithm, sensor networks.

Constructing belt-barrier providing β-quality of monitoring with minimum camera sensors

A wireless sensor network is said to form a belt-barrier for a region if it is able to detect any object moving from outside the region to inside. Recently, Cheng and Tsai found if camera sensors are used to form a belt-barrier, the breadth of the barrier becomes an important quality factor to ensure high quality of monitoring (QoM). Then, they proposed the minimum β-breadth belt-barrier construction problem ((β, 1)-B3CP) whose goal is to select a minimum number of camera sensors to form a β-breadth belt-barrier, which ensures the width of the picture of any object which moves through the barrier is at least β. In this paper, we perform more thorough investigation of the problem and introduce a new polynomial time exact algorithm for the problem under the assumption that the angle of each camera is fixed. Our simulation result shows our algorithm outperforms Cheng and Tsais algorithm. We also introduce a variation of (β, 1)-B3CP, namely (β, k)-B3CP, which aims to construct k node-disjoint β-breadth belt-barrier for fault-tolerance purpose, propose a new heuristic algorithm for it, and conduct simulations to evaluate its performance.