Interleaver design methods for turbo codes

Abstract

It is generally assumed that when a turbo decoder is operating at low bit error rates, error sequences have small Hamming weights. From this, and properties of turbo encoders, a mathematical structure is developed for interleaver design, permitting the identification of quantitatively optimal interleavers. Simulations show the math captures some but not all the essential characteristics of a successful interleaver. Modifying a random interleaver according to the mathematical ideas gives excellent simulation results.