A farmland multimedia data collection method using mobile sink for wireless sensor networks

Wireless sensor networks are applied to collect the information about farmland required to achieve unmanned agriculture. The major purpose of the deployed sensors is to collect data. However, if the data collected by the sensors are too large, such as an image, sensors quickly become unavailable. In this paper, a novel method for collecting image data from deployed sensors by using a mobile sink is proposed. Unlike the existing data gathering methods, in which sensors deliver data to a sink via long distance transmission, in the proposed method the mobile sink walks within the region of interest (ROI) to harvest the data. A virtual-grid method is proposed to determine the visiting locations of the mobile sink. An algorithm to eliminate redundant locations that uses set-conjunction operations is also proposed for reducing the number of unnecessary visiting locations. In addition, a cross-edge adjusting trajectory scheduling (CATS) algorithm is proposed to reduce the moving distance of the mobile sink. Simulation results show that the proposed virtual-grid method can effectively reduce the number of visiting locations by about 15-20 % as compared to the cluster-centroid method. The CATS algorithm can also shorten the moving distance of the mobile sink by about 25 % as compared to that of a heuristic minimum spanning tree method.