Merging codebook based codeword position index modulation scheme for SCMA.

To meet the rigorous demands for reliability and spectral efficiency (SE) in the beyond-5th generation mobile network (5G) and the upcoming 6th generation mobile network (6G), a merging codebook based codeword position index modulation scheme for sparse code multiple access (SCMA) is proposed for the uplink SCMA. The scheme expands the codeword position in the time domain, allowing the codeword positions to be fully populated and carry additional information bits by their index, and provides flexibility in adjusting the system SE by changing the codeword position number and the index modulation order. Furthermore, a corresponding joint detection algorithm based on message passing algorithm (MPA) is designed and the design criteria of the merging codebook are given. System analysis and simulation results show that compared with other index modulation schemes, the proposed scheme better balances reliability and SE, and also has advantages in bit error rate (BER) performance and robustness. [ABSTRACT FROM AUTHOR]