A note on permutation modulation

Slepian (1962) observed that the code points in an n-dimensional variant-1 permutation modulation code actually lie in an n-1-dimensional subspace. In this correspondence, a change of coordinates which gives the representation explicitly in n-1 dimensions is derived. Slepian's optimum decoding algorithm can be adapted to the codes in this form using an idea of Biglieri and Elia (1976).