Novel BICM HARQ Algorithm Based on Adaptive Modulations

Abstract

A novel type-II hybrid automatic repeat request (HARQ) algorithm using adaptive modulations and bit-interleaved coded modulation (BICM) is presented. The algorithm uses different optimized puncturing patterns for different transmissions of the same data packet. The proposed approach exploits mapping diversity through BICM with iterative decoding. The modulation order is changed in each transmission to keep the number of symbols transmitted constant. We present new bit error rate and frame error rate analytical results for the proposed technique showing good agreement with simulation results. We compare the throughput performance of our proposed HARQ technique with a reference HARQ technique that uses different mapping arrangements but keeps the modulation order fixed. By using optimized puncturing patterns and adaptive modulations, our method provides significantly better throughput performance over the reference HARQ method in the whole signalto- noise ratio (SNR) range, and achieves a gain of 12 dB in the medium SNR region.