In real world wireless sensor network applications, data gathering is an major issue,by means of data gathering increase the network life time.This means minimum energy should be consumed and transmission should occur with minimum delay which are conflicting requirements. Energy and delay are the major parameter for lifetime of any wireless sensor network.Efficient data gathering reduces the number of data transmission and consume less power. Это и многое другое вы найдете в книге Insight into Data Gathering in Wireless Sensor Networks (Ganesh Kumar P. and Muthu Krishnan A.)