Adaptive Interleaver and Rate-Compatible PLDPC Code Design for MIMO FSO-RF Systems

This paper conducts an in-depth investigation on the interleaver and error-correction codes for multiple-input multiple-output (MIMO) hybrid free space optical-radio frequency (FSO-RF) systems. Specifically, based on the unequal error protection (UEP) property between the FSO links and RF links, we first propose a novel adaptive interleaver, called protograph variable-node mutual information growth match (PVMIGM) mapping scheme , to boost the performance of MIMO FSO-RF systems with protograph low-density parity-check (PLDPC) codes. Furthermore, by exploiting the protograph extrinsic information transfer (PEXIT) algorithm, we design a type of rate-compatible PLDPC code, called improved rate-compatible PLDPC (IRP) codes , which have both low decoding thresholds and effective typical minimum distance ratios (TMDRs). Simulation results demonstrate that our proposed designs outperform the state-of-the-art counterparts.