- In this paper, we propose a new method to design an interleaver with practical size for turbo codes. In order to construct an optimal interleaver, we first set up the following design rules: (i) to suppress the interleaver correlation; (ii) to break up self-terminatingweight-2 input sequences;and (iii) to avoid edge effects.We then synthesize a new type of interleaver structure, starting with the conventional block interleaver and applyingsimple transformationsteps. The resulting interleaver can createturbo codes with relativelysmall block size that yield better performance than previously known interleavers. Advantages of the new interleaver are demonstrated by conducting comprehensive comparisons based on both theoreticalanalysesand computersimulations.