Abstract
In the paper, we investigate LDPC-coded differential amplitude/phase modulation (APM) schemes for correlated Rayleigh fading channels. Through the observation for the mutual information of the extrinsic log-likelihood ratio (LLR) values of the variable nodes in the LDPC decoder, it is found that the code design methods investigated in the previous literature loses their accuracy. Consequently, a modified code design method for the outer LDPC code is proposed in this paper. It is shown that the searched LDPC code effectively improves the error performance, when compared to the convolutional-coded scheme investigated in the previous literature.