Approximation algorithm for data gathering from mobile sensors

In Wireless Sensor Network (WSN), sensors are deployed to sense useful data from environment. To prolong the sensor network lifetime in large-scale network, mobile sinks are employed for collecting data from the sensors directly. The major drawback of the system is slow speed of the mobile sinks, which causes long data gathering delay from the sensors. Since, sensors have limited memory and hence it causes buffer overflow in the sensors. Therefore, to avoid buffer overflow the data must be gathered by the mobile sinks within a predefined time interval. Data gathering from mobile sensors using mobile sinks is more challenging problem than data gathering from static sensors. A set of mobile sensors are moving arbitrarily on a set of predefined paths. Our objective is to collect data periodically from all mobile sensors using minimum number of mobile sinks and subsequently the mobile sinks visit a base station (BS) for final data delivery. We show that the problem is NP-hard and two approximation algorithms are proposed. We extend the proposed algorithms, where mobile sensors can deliver their sensed data to mobile sink within their circular communication regions and present a recovery algorithm from mobile sink's failure. We analyze the performance and time complexity of the proposed algorithms.