INFORMATION INTEGRATION AND SYNCHRONIZATION IN DISTRIBUTED SENSOR NETWORKS

In recent years, the study of systems with multiple sensors has been an active area of research. In the paper, the authors focus on the computational, i.e., architectural, algorithmic, and synchronization issues related to competitive information integration in a distributed sensor network (DSN). The proposed architecture of the DSN consists of a set of binary trees whose roots are fully connected. Each node of the tree has a processing element and one or more sensors associated with it. The information from each of the sensors has to be integrated in such a manner that the communication costs are low and that the real time needs are met. An information integration algorithm that has a low message cost (linear in the number of nodes of the network) and a low distributed computation cost is presented. In a distributed environment there is no central clock that regulates the activities of each node. Further, the clock at each node is typically not accurate. The estimates from each of the sensors that need to be integrated have to be temporally "close to each other," however. The problems associated with synchronizing information to be integrated in the presence of imperfect clocks is considered. The relationships between the clocks of the processing elements in the network for proper information integration and an upper bound on the period between consecutive resynchronizations of a processing element's clock with the central time server are derived. Finally, the fault tolerant features of the network and the integration algorithm are discussed.