  This paper considers the state estimation problem for discrete-time linear
systems under event-triggered scheme. In order to improve performance, a novel
event-triggered scheme based on confidence level is proposed using the
chi-square distribution and mild regularity assumption. In terms of the novel
event-triggered scheme, a minimum mean squared error (MMSE) state estimator is
proposed using some results presented in this paper. Two algorithms for
communication rate estimation of the proposed MMSE state estimator are
developed where the first algorithm is based on information with one-step
delay, and the second algorithm is based on information with two-step delay.
The performance and effectiveness of the proposed MMSE state estimator and the
two communication rate estimation algorithms are illustrated using a target
tracking scenario.
