Collaborative Area Monitoring Using Wireless Sensor Networks with Stationary and Mobile Nodes

EURASIP Journal on Advances in Signal Processing, Dec 2009

Monitoring a large area with stationary sensor networks requires a very large number of nodes which with current technology implies a prohibitive cost. The motivation of this work is to develop an architecture where a set of mobile sensors will collaborate with the stationary sensors in order to reliably detect and locate an event. The main idea of this collaborative architecture is that the mobile sensors should sample the areas that are least covered (monitored) by the stationary sensors. Furthermore, when stationary sensors have a "suspicion" that an event may have occurred, they report it to a mobile sensor that can move closer to the suspected area and can confirm whether the event has occurred or not. An important component of the proposed architecture is that the mobile nodes autonomously decide their path based on local information (their own beliefs and measurements as well as information collected from the stationary sensors in a neighborhood around them). We believe that this approach is appropriate in the context of wireless sensor networks since it is not feasible to have an accurate global view of the state of the environment.

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Collaborative Area Monitoring Using Wireless Sensor Networks with Stationary and Mobile Nodes

EURASIP Journal on Advances in Signal Processing Hindawi Publishing Corporation Collaborative Area Monitoring Using Wireless Sensor Networks with Stationary and Mobile Nodes Theofanis P. Lambrou 0 Christos G. Panayiotou 0 0 KIOS Research Center for Intelligent Systems and Networks, Department of Electrical and Computer Engineering, University of Cyprus , Nicosia 1678 , Cyprus Monitoring a large area with stationary sensor networks requires a very large number of nodes which with current technology implies a prohibitive cost. The motivation of this work is to develop an architecture where a set of mobile sensors will collaborate with the stationary sensors in order to reliably detect and locate an event. The main idea of this collaborative architecture is that the mobile sensors should sample the areas that are least covered (monitored) by the stationary sensors. Furthermore, when stationary sensors have a “suspicion” that an event may have occurred, they report it to a mobile sensor that can move closer to the suspected area and can confirm whether the event has occurred or not. An important component of the proposed architecture is that the mobile nodes autonomously decide their path based on local information (their own beliefs and measurements as well as information collected from the stationary sensors in a neighborhood around them). We believe that this approach is appropriate in the context of wireless sensor networks since it is not feasible to have an accurate global view of the state of the environment. 1. Introduction Recent progress in two seemingly disparate research areas namely, distributed robotics and low power embedded systems has led to the creation of mobile sensor networks [ 1 ]. Autonomous node mobility not only brings with it its own challenges, but also alleviates some of the traditional problems associated with static sensor networks. It is envisaged that in the near future, very large scale networks consisting of both mobile and static nodes will be deployed for applications ranging from environmental monitoring to military applications [ 2 ]. In this paper we consider the problem of monitoring a large area using wireless sensor networks (WSNs) in order to detect and locate an event. In this context, we assume that the event emits a signal that is propagated in the environment. The sensors capture attenuated and noisy measurements of the signal and the objective is to reliably detect the presence of the event and estimate its position. By reliably we mean that we would like to minimize the probability of miss event (an event that remains undetected) subject to a constraint on the probability of false alarms (the sensors report an event due to noise). Note that in many applications false alarms are as bad (if not worse than) as missed events. In addition to the incurred cost for sending response personnel to the area of the event, frequent false alarms may lead the users to ignore all alarms, and as a result even detected events will go unnoticed. To achieve reliable detection in a large area, it is necessary to deploy a huge number of sensors which with the current technology implies a prohibitive cost [ 3 ]. For example, consider a lake to be monitored for events (an event can be a boat that spills a substance in the lake that changes the water turbidity). If the lake has an area of 20 km × 20 km, and we assume that each sensor has a reliable sensing range (detection range) rd=10 m, then the number of sensor nodes needed to monitor the entire lake is of the order of 106 which with today’s technology implies a prohibitive cost. Given that it is infeasible to reliably cover the entire area with stationary nodes, in this paper we investigate an alternative way of monitoring the area using several stationary and some mobile sensor nodes that collaborate in order to improve the area coverage and/or to detect an event as fast as possible. The main idea is that the mobile nodes will collaborate with the stationary nodes (and with each other) in order to sample areas that are least covered by the stationary nodes. In the context of WSNs, sensor nodes are fairly inexpensive and unreliable devices, thus it is not feasible to have an accurate state of each sensor node in the field (some nodes may have failed or been carried away). As a result one cannot have all necessary information to centrally solve a path planning problem and predetermine the path that each mobile sensor node should follow in order to sample the areas least covered. In the proposed approach, mobile nodes navigate through the sensor field autonomously using only local information (i.e., the mobile node’s beliefs and measurements as well as information collected from the nodes, stationary or mobile, that are in a neighborhood around the mobile). This paper investigates the use of signal processing techniques in the path planning of mobile agents for improving the area monitoring in the context of WSNs. The mai (...truncated)


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Theofanis P. Lambrou, Christos G. Panayiotou. Collaborative Area Monitoring Using Wireless Sensor Networks with Stationary and Mobile Nodes, EURASIP Journal on Advances in Signal Processing, 2009, pp. 750657, Volume 2009, Issue 1, DOI: 10.1155/2009/750657