Improving turbo codes through code design and hybrid ARQ

We consider techniques to improve the performance of coded communication systems. Turbo codes have been shown to provide performance close to the channel capacity for long block sizes. The performance of turbo codes can be improved through several different techniques including code concatenation, automatic repeat request (ARQ) and rate adaptation. We first investigate techniques to evaluate the performance of turbo-like codes and design better codes. Then, we identify techniques to further improve the performance of turbo codes through code concatenation and hybrid ARQ. The performance of serial-concatenated codes that utilize turbo code as inner codes and rectangular parity check code (RPCC) as outer codes is investigated with reliability-based hybrid ARQ (RB-HARQ). Also, we investigate the performance of turbo codes with RB-HARQ and rate adaptation. The results show that these reliability-based hybrid ARQ techniques can provide significant performance gains. Finally, we propose a new HARQ approach that has the potential to reduce decoding complexity and increase performance at high signal-to-noise ratios.