Hierarchical Fusion in Clustered Sensor Networks with Asynchronous Local Estimates

This letter investigates the hierarchical fusion estimation for clustered sensor networks. The sensors within the same cluster are connected to a local estimator, and all the local estimators are linked with a fusion center. The fusion center and the local estimators are not required to be synchronous. During each estimation interval, the sensors are allowed to communicate with the local estimator several times. A minimum variance estimation algorithm is presented for each cluster to aperiodically generate local estimates. A covariance intersection fusion strategy is presented for the fusion center to generate fused estimates by using asynchronous local estimates and previous fused estimates, without knowing the cross-covariances among the local estimation errors.