The LDPC-Coded High-Dimensional SCMA Codebook Design

Sparse code multiple access (SCMA) and low density parity check (LDPC) are two promising technologies in 5G New Radio communications. In this paper, the LDPC codes are adopted as the channel coding to ensure the transmitted data is revived with minimal errors. Then, we propose a new method for constructing the high-dimensional SCMA codebook. However, the complexity of the message passing algorithms (MPA) based detectors are extremely high, which conflicts with the low latency demand of the 5G wireless communication systems. To save the computational costs of the SCMA detector, we fully exploited the information of the SCMA codebook, and introduce the successive interference cancellation (SIC) algorithm as the detector. In the LDPC-coded scheme, the SIC decoding algorithm lose the information of minimum Euclidean distance of other codewords, which cause the better BER performance disobeys the principles of increased code length and the decreased code rate while the coding scheme can also improve the BER performance. The simulation results show the LDPC-coded SCMA scheme can achieve preferable bit error rate (BER) performance, and the SIC detector can significantly reduce the complexity at the receiver.