Collecting sensory data with the mobile sink often entails several issues, such as dynamic repositioning of a sink, exhaustive routing tree updates, and data loss from unexpected movement of a sink.
In this paper the mobile sink based network protocol which we call ``mUSN (mobile Ubiquitous Sensor Networks)’ will be introduced. mUSN is designed to handle mobility of the sink in energy-efficient and reliable ways. Assuming that all the nodes in the network including a sink know their geographic location using their localization engine, mUSN provides a method of alerting nodes by analyzing changes in the movement vector of the sink. Also by controlling the number of updates of a routing tree, it prohibits unnecessary energy and time consumption due to significant routing packet transmission.