Efficient distance measurement method for turbo codes that use structured interleavers

This letter presents an efficient and accurate distance measurement method for tail-biting turbo codes that use structured interleavers. This method takes advantage of the structure in the interleaver as well as the circular property of tail-biting. As such, it significantly reduces the computational complexity, which allows the accurate determination of high minimum distance (d_min) in reasonable time. The efficiency of this method is demonstrated by its ability to determine the true d_min of 51 and the corresponding true multiplicities for a rate-1/3 turbo code that uses the UMTS 8-state polynomial generators and an MPEG-sized interleaver (1504 information bits) in reasonable time