Noncausal filters: possible implementations and their complexity

Possible solutions for noncausal filter implementation are considered. Detailed calculation of the performance parameters associated with each possible solution is provided. Such calculation shows that the number and the position of the system poles affect the performance of each solution. This can have a profound impact over many linear-filtering applications where the designed filter is periodically adapted without constraining the poles to lie inside the unit circle and, at each adaptation step, the structure for its implementation has to be automatically chosen.