LDPC Coded Link Adaptation Based on Irregular Modulation Integrated with Full Incremental Redundancy

The irregular modulation (IM) technique was initially proposed in bit-interleaved coded modulation (BICM) for convolutional code and turbo code cases (Schreckenbach and Bauch, 2006), which apply different signal constellations and mappings within one codeword. The IM technique gives a simple method to improve flexibility of BICM, which can also provide an adaptive modulation with fine granularity. We combine the IM and low density parity check (LDPC) coded full incremental redundancy (FIR) hybrid automatic repeat request (HARQ) to propose a novel link adaptation method-"IM_FIR". Simulation results show that the "IM_FIR" can not only achieve higher throughput efficiency but also significantly reduce transmission delay than the LDPC coded regular modulation with FIR schemes. Furthermore, an adaptive IM with FIR scheme is presented, which can adaptively select proper IM strategies to get highest throughput in accordance with variations of the channel conditions.