A joint detection decoding scheme for non-binary LDPC and SCMA system
In order to solve the problem of high complexity,high bit error rate,large transmission delay and slow convergence rate existing in current joint detection scheme including low-density parity code(LDPC)and sparse code multiple access(SCMA),a joint detection decoding(JDD)scheme,with the combination of non-binary low-density parity code(NB-LDPC)and SCMA sys-tem,was proposed.The threshold-assisted expectation propagation algorithm(EPA)in SCMA was improved,NB-LDPC was adopted in the LDPC part and some message status values were selected in the update process of two nodes to improve the decoding algorithm.Meanwhile,a message damping factor was added to the joint factor diagram when decoding information during joint detec-tion was exchanged.Then joint detection decoding process was completed.Through multi-angle simulation,it is found that the scheme reduces the complexity,the bit error rate and the transmission delay,improves the convergence speed,and verifies the appli-cability of the proposed scheme under different code books.
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