Low-Complexity Multiple-Component Turbo-Decoding-Aided Hybrid ARQ

Previous research has focused on improving the throughput of hybrid automatic repeat request (HARQ) schemes. However, since turbo codes have been introduced into HARQ schemes, their complexity has increased owing to the iterative Bahl-Cocke-Jelinek-Raviv (BCJR) operations that are required following each retransmission. This paper explores the complexity of turbo HARQ schemes and proposes a new early stopping (ES) approach for iterative decoding based on mutual information (MI), which dynamically determines the appropriate number of BCJR operations to be performed following each incremental redundancy (IR) transmission. We demonstrate that the proposed ES-based multiple-component turbo code (MCTC)-aided and systematic twin-component turbo code (TCTC)-assisted HARQ schemes exhibit 60%-85% reduced complexity for signal-to-noise ratios (SNRs) below -2 dB without degrading the packet-loss ratio (PLR) and the throughput.