A Novel SCMA Codebook Design Method Based on Low Error Probability Criteria

A method to construct codebooks for downlink sparse code multiple access (SCMA) systems is proposed in this paper. Codebooks for each sub-channel are based on the most commonly used QAM modulation. Then, low error probability criteria to measure the SCMA codebook performance in AWGN channel and Rayleigh fading channel are proposed. We propose to use simulated annealing algorithm to optimize the proposed codebooks based on the criteria. Simulation results show that the proposed codebooks exhibit excellent performance in both Rayleigh fading channel and AWGN channel, especially for high-order SCMA systems.