Convolutional Code Search for Good Permutation Trellis Codes using M-ary FSK

Permutation trellis codes combined with M-ary FSK are considered with the aim of combating additive noise, impulse noise and permanent frequency disturbances. New permutation trellis codes are presented that were found by exhaustive computer search, considering the free distance and the distance spectrum of the codes. Until now the best binary convolutional codes were considered to be the best candidates to use in mappings for trellis codes, however the results will show that this is not always the case. Simulation results are also presented, showing that in most cases the new permutation trellis codes are performing better than the previous codes, although the gains attained are small.