Optimal filtering and smoothin with fixed delay in digital linear systems for a selected series of points

Algorithms of filtering and smoothing are developed with fixed delay of states in digital dynamic systems which differ from the conventional algorithms in that the states are estimated, rather than at every digital time, only in a selected series of equidistant points in a time sequence. The computer load in dealing with systems where the parameters are constant or periodically varying with time is reduced when these algorithms are used instead of conventional ones.