I'm pretty sure this paper was generated by a bot. Aside from phrases like "The evaluation of the WHTs product needs only real multiplications by +1 or 1" I see phrases culled from expired patents. Googling pulls up a more interesting paper from the 70s. This is weird.
I had a large interest in discrete convolution operations a few years ago, particularly in application to digital image processing. Two papers that I published may be of interest to those here:
[A paper that as a lemma demonstrates the influence of boundary conditions on the use of discrete orthogonal transformations for fast convolution operations] https://scholar.google.com/citations?view_op=view_citation&h...
[accelerating convolution operations when a matrix factorization (SVD, DCT for jpeg, etc.) is already available]
https://scholar.google.com/citations?view_op=view_citation&h...