Research On Some Issues Of Ocean Monitoring Wireless Sensor Networks

In modern practical applications, wireless sensor networks are widely deployed to implement the ocean monitoring both on and under surface by having all sensor nodes work cooperatively with advanced technologies of wireless communication, control and computation. This thesis mainly focuses on the issues of two-dimensional node positioning at sea surface, three-dimensional underwater node positioning, sea surface coverage and target tracking, which can be summarized as follows:For surface two-dimensional node positioning, an improved DV-Hop algorithm is proposed. By combining the distance precision of known nodes, the correction of average distance of unknown nodes at every hop distance and steepest descent with Taylor series method, node localization precision is significantly enhanced.To deal with the problem of three-dimensional underwater location, a TOA algorithm is presented based on anchor node constraints and weighted least squares. To begin with, the problem of three-dimensional location is transformed into one of two-dimensional location. The positions of unknown nodes are estimated by three known nodes with angle constraints which must be not in a straight line. Moreover, considering the effects of signal transmission time and speed in water on errors, the weighted least square algorithm is used for estimation of node location.Coverage of marine monitoring sensor networks is addressed by developing an improved algorithm of fast virtual force subject to random waves. By setting up the attraction area and simplifying the scope of virtual force, the total force of nodes is comprehensively analyzed. According to the different energy consumption of node movement arising from diverse flow direction, a movement strategy is correspondingly provided such that the rate of coverage is increased while consuming less energy of nodes.Trajectory prediction of pollutants, positioning of target and tracking nodes, and target tracking are investigated. By employing a Kalman filter method, the actual trajectory of oil is predicted. Applying semi-definite relaxation programming, the positions of target and tracking nodes are obtained. Then, the tracking error system is established. Based on a Lyapunov method, a condition on the existence of state feedback controller is derived such that the tracking error system can be guaranteed to be asymptotically stable under communication constraints.Finally, the contributions of the dissertation are summarized, and the outlook for ocean monitoring over wireless sensor networks is provided.