In this paper, the authors investigate the problem of gathering the data in wireless sensor network using a single Mobile Element. In particular they consider the case where the data are produced by measurements and they need to be delivered to a predefined sink within a given time interval from the time the measurement takes place. A mobile element travels the network in predefined paths, collect the data from the nodes, and deliver them to the sink by a single long-distance transmission. In this problem, the length of the mobile element path is bounded by pre-determined length. This path will visit a subset of the nodes. These selected nodes will work as caching points and will aggregate the other nodes' data.