Analysis of reliability-based incremental redundancy with convolutional codes

Incremental redundancy, or hybrid type-II ARQ (HARQ), algorithms use a combination of forward error correction and retransmissions to guarantee reliable packet data communication. In our previous work (V. Tripathi et al. 2003), we have proposed an adaptive HARQ algorithm that exploits received codeword reliability for optimizing the size of the subsequent retransmissions. The optimization is based on two mappings: the codeword reliability to block error rate (BLER) mapping and the coding rate to codeword reliability mapping. We provide analytical approximations for these mappings for any convolutional code. Through simulations, the approximations are shown to be accurate in the range of interest.