A new approach to UEP-HARQ via convolutional codes

This letter presents a novel type-II hybrid automatic repeat request (HARQ) transmission scheme which is based on pruned convolutional codes (CCs) and supports unequal error protection (UEP). The data to be transmitted is assumed to consist of important bits (IB) and standard bits (SB). In the proposed scheme, all the bits are first encoded using a single mother CC and transmitted over the channel. If a decoding error is detected in the IB, then retransmission of only the IB takes place using a CC, typically with a better error correction capability. Next, taking advantage of the properties of pruned CCs, the decoded IB are used to increase the decoding reliability for the SB. Numerical simulations indicate that the proposed scheme offers strong protection for the IB along with improved reliability for the remaining bits compared to other UEP schemes.