Projective filtering of time warped ECG beats

The paper proposes a modification of the nonlinear state-space projections (NSSP) method. Our approach, when applied to ECG signal processing, considerably improves the method's performance. One of the crucial operations in NSSP is the search for neighborhoods of the state-space trajectory points. The modification proposed is based on imposing a few restrictions on the time location of the neighborhood points. Dynamic time warping, a technique which allows for nonlinear alignment of time series or sequences of vectors, is applied as a straightforward solution to the task of neighborhoods determination with the restrictions imposed. The influence of nonlinear alignment on the distributions of the determined neighborhoods is presented, and the resulting method of ECG enhancement is investigated.