  In a sensor network, some sensors usually provide the same or equivalent
measurement information, which is not taken into account by the existing secure
state estimation methods against sparse sensor attacks such that the
computational efficiency of these methods needs to be further improved. In this
paper, by considering the observation equivalence of sensor measurement, a
concept of analytic sensor types is introduced based on the equivalent class to
develop a fast state estimation algorithm. By testing the measurement data of a
sensor type, the attack location information can be extracted to exclude some
mismatching search candidates, without loss of estimation correctness. This
confirms high speed performance of the proposed algorithm, since the number of
sensor types is usually far less than the number of sensors.
