Incidence Colorings of Powers of Circuits

The incidence chromatic number of G is the least number of colors such that G has an incidence coloring. It is proved that the incidence chromatic number of Cn^p, the p-th power of the circuit graph, is 2p ＋ 1 if and only if n = k（2p ＋ 1）, for other cases： its incidence chromatic number is at most 2p ＋ [r/k] ＋ 2, where n = k（p ＋ 1） ＋ r, k is a positive integer. This upper bound is tight for some cases.