Free distance computation of turbo BCH codes

The paper presents an algorithm for the free distance determination of turbo Bose Ray Chaudhuri Hocquenghem (BCH) codes constructed by row-column interleavers. The algorithm calculates the minimum weights of turbo BCH codes obtained from input bitstreams having different weights. Among the minimum weights calculated in different cases, the minimum one is being considered as the free distance of turbo BCH codes. This is being achieved applying specifications of the interleaver and constituent BCH codes. Based on the computed free distances, the upper bound of probability of error for different turbo BCH codes is determined. It agrees with simulation results of the code performance in the error floor region.