ON CROSSTALK-FREE BPC PERMUTATIONS ROUTING IN AN OPTICAL VARIABLE-STAGE SHUFFLE-EXCHANGE NETWORK

摘要

The paper introduces an approach for crosstalk-free bit-permute-complement (BPC) permutations routing in hybrid optical variable-stage shuffle-exchange networks (SENs) of size N × N where N=2~n, and the number of stages m can vary in 1 ＜ m ≤ 2n - 1. The number of stages should be asserted as required by a given BPC permutation for its admissibility. The crosstalk is caused by interacting of two optical signals within the same switch, it can be avoided by decomposing a given permutation to partial permutations which exclude such coupling. In an ideal case the partial permutations should be two semi-permutations with each realizable for one pass through the network. The proposed O(NlogN) algorithm provides an optimal solution for m-stage optical SEN with m in the range, but for n ＜ m ≤ 2n - 1 produced semi-permutations might require further decomposing. It depends on the construction of transition matrix, which can be different for the same BPC permutation. Some guidelines for this case are given.