Wireless sensor networks that operate on batteries have limited network lifetime. There have been extensive recent research efforts on how to design protocols and algorithms to prolong network lifetime. However, due to energy constraint, even under the most efficient protocols and algorithms, the network lifetime may still be unable to meet the mission's requirements. In this paper, background knowledge on data uploading solutions in Wireless Sensor Networks (WSNs) is firstly provided.

Keywords: energy constraint,networklifetime,wireless sensor networks(WSNs).;