Investigating Mother Constellation of SCMA Systems Having Capability of Multiuser Detection

Codebook design is an important factor determining the performance of sparse code multiple access (SCMA) systems. By properly designing the mother constellation, a codebook will be obtained for each user on the SCMA system. In this paper, we investigate mother constellation for SCMA system having capability of multi user detection $Q$. Two types of constellation are used in this paper, line constellation, where symbols/codebooks owned by each user are distinguished by amplitude, and square constellation, where symbols/codebooks owned by each user are distinguished by phase. Simulation results confirmed that line constellation has better bit error rate (BER) performances compare to square constellation at $L=2$. Higher $L$ in MUD $Q$ needs higher signal to Noise Ratio (BER) to obtain same BER.