Data Gathering from Path Constrained Mobile Sensors Using Data MULE
  In Wireless Sensor Network (WSN) sensor nodes are deployed to sense useful data from environment. Sensors are energy-constrained devices. To prolong the sensor network lifetime, now a days mobile robots (sometimes refer as data sink, data mules, or data collectors) are used for collecting the sensed data from the sensors. In this environment sensor nodes directly transfer their sensed data to the data mules. Sensed data are sometime time sensitive; therefore, the data should be collected within a predefined period. Hence, depending on the speed of the data mules the trajectory lengths of the data mules have upper limits. In this paper an approximation algorithm is proposed for collecting data from the mobile sensors using mobile data collectors 
Dinesh Dash
cs.NI