Polycyclic codes over Galois rings with applications to repeated-root   constacyclic codes
  Cyclic, negacyclic and constacyclic codes are part of a larger class of codes called polycyclic codes; namely, those codes which can be viewed as ideals of a factor ring of a polynomial ring. The structure of the ambient ring of polycyclic codes over GR(p^a,m) and generating sets for its ideals are considered. Along with some structure details of the ambient ring, the existance of a certain type of generating set for an ideal is proven. 
Sergio R. Lopez-Permouth, Hakan Ozadam, Ferruh Ozbudak, Steve Szabo
math.RA cs.IT math.IT