A time delaying model of farmland moisture sensor networks

Farmland moisture sensor network (FMSN) has the characteristics of ultra-large-scale, cheap and unreliable sensor nodes which bring more difficult in moisture data gathering, especially in time synchronization. Since sensor clocks are imperfect, local clock of nodes may drift away from each other in a period of time. Thus observed time or time intervals may differ in each node in the network while collecting moisture information. In this paper, a time delaying model for large-scale FMSN is proposed, which takes the interaction with disposal space distance, transmission semi-diameter, size of packet as well as the impact of components into account. Furthermore, given the disposal space distance, an algorithm to calculate time delay is presented. Above model and algorithms has been used in our project of Congyu FMSN which can guarantee the network work orderly.