The symbol-pair distance distribution of repeated-root cyclic codes over   $\mathbb{F}_{p^m}$
  Symbol-pair codes are proposed to protect against pair errors in symbol-pair read channels. One of the most important task in symbol-pair coding theory is to determine the minimum pair-distance of symbol-pair codes. In this paper, we investigate the symbol-pair distances of cyclic codes of length $p^e$ over $\mathbb{F}_{p^m}$. The exact symbol-pair distances of all cyclic codes of such length are determined. 
Shixin Zhu, Zhonghua Sun, Liqi Wang
cs.IT math.IT