Cooperative And Energy-Efficient Target Tracking In Wireless Sensor Networks

Current developments in Wireless Sensor Networks (WSNs) technology provide increasing opportunities to analyze target behavior and monitor environmental processes in a changing world. Target tracking is typically a thought-provoking application in WSNs because it is always computation-intensive, energy constrained and requires real-time processing. However, maximizing the lifetime of wireless sensor networks used for tracking a moving target depends greatly on minimizing transmission power levels, volume of messages, time for neighbor discovery operations, and especially on selecting a number of sensors at a given time. A variety of literatures have been studied concerning these issues mentioned above for target tracking in sensor networks. As a result, a novel cooperative and energy-efficient target tracking protocol in wireless sensor networks (CET) is proposed to reduce energy consumption for tracking mobile targets in WSNs in terms of sensing and communication energy consumption.An entity that intends to track a target is called a tracker. A tracker is assumed to be a single generic source such as a mobile user or a respective authority. A target can be any moving object such as an enemy vehicle, an intruder, or a moving fire. Each sensor in the network has the capability of sensing, communicating, and computing. One of the active and working sensors is elected as a Monitor, and another one is elected as a Backup for fault tolerance concern. In a case that the monitor has any problem due to any reason, the backup will take the role of the monitor. The monitor can work at request of the tracker. Each monitor is capable of computation. After finishing a task, the monitor changes its state. In order to maintain the state of operation, a special wakeup mechanism is designed, by using the mechanism via which CET takes advantage of the energy saving feature in sensor networks. While the monitors go to active state one after the other and the other sensors typically stay in a periodic inactive or awaking state.This work is described by using relative neighborhood based on the concept of face-aware routing, and assuming the network to be modeled as a unit disk graph and sensor nodes to be placed in a two-dimensional Euclidean space. However, face-aware routing is described by the concept of relative neighborhood graph (RNG) and Gabriel graph (GG) of a finite planner set of points in the Euclidean plane. There are five steps to describe the overall target tracking process, namely, target initialization, target detection, tracker movement, location and direction estimation, and monitor and backup election process.The main motivation of our work is to shorten target capturing time and prevent the chance of target missing if there is any incident of node failure, routing failure, or loss of tracking. In real WSNs, node or link failure is often possible. In this thesis, the proposed CET protocol avoids unpredicted failures through the cooperation of sensors. More specifically, if there is a missing or failure event, we allow neighbor sensors close to the monitor in the face to cooperate. Even in this state, if the target is not sensed, we allow all the neighbors in the face to relocate the target. If the target is still not sensed, we allow all the neighbor sensors in close proximity of the face to relocate the target. Even when all the neighbors fail, CET reverts to the initial state.An energy saving prediction-based method is demonstrated for estimation of the target's location and direction, and two dimensional Gaussian distribution is applied to predict the future location of the target. Once the future location of the target is known, a new monitor and a backup are elected. The main assumption made by this CET is that each node in the network can locally estimate the cost of sensing, processing, and communicating data to another node.A simulation environment is developed using OMNet++ software. An extensive observation is performed and the necessary experimental data for this research is collected from in-depth study. The experiments are performed in regard to four evaluation metrics, i.e. 1) missing rate; 2) first capturing time; 3) prediction error; 4) average energy consumption, and 5) packet overhead. Performance analysis and simulation studies show that CET outperforms existing two target tracking protocols. The tracker can capture the target comparatively faster, due to the fact that the tracker does not need to often use the flooding mechanism. The proposed protocol greatly contributes to energy conservation by simplifying sensor's calculation, and minimizing the volume of messages exchanged between sensors as well as sensors and tracker. The number of packet overhead is gradually increased in CET compared to existing two protocols while the tracker velocity increases.