Date Added: Dec 2011
Although commonly considered as harm in wireless networks, mobility can potentially be beneficial to wireless sensor networks that usually consist of static nodes. A recent boom of applying mobile devices to improve the lifetime of wireless sensor networks has lead to a great deal of meaningful contributions, both in theory and practice. In this paper, the authors survey the efforts relevant to this topic. In addition, they also identify the lack of theoretical understanding of one of the approaches, namely mobile sink.