Cost based in-network join strategy in tree routing sensor networks

The tiny and smart sensors enable applications which access a network of hundreds or thousands of sensors. In many applications, joins are used frequently to find relationships of readings of different sensors such as the correlation of sensor readings in distinct regions. In this paper, we present a cost based in-network join strategy called INJECT. Since the optimal join plan is determined according to various conditions such as data distributions and predicates of joins, it wastes the energy of sensors to use a fixed join plan blindly. Based on the analysis on how join queries can be handled in sensor networks, we devise several join plans. In particular, since the data transmission dominates the energy consumption of a sensor, we devise cost models each of which reflects the transmission cost of a join plan. Experimental results confirm that INJECT chooses the optimal or near optimal plan under various conditions.