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In this paper, we propose to use golden angle modulation (GAM) points to construct codebooks for uplink and downlink sparse code multiple access (SCMA) systems. We provide two categories of codebooks with one and two optimization parameters respectively. The advantages of the proposed design method are twofold: 1) the number of optimization variables is independent of codebook and system parameters; 2) it is simple to implement. In the downlink, we use GAM points to build a multidimensional mother constellation for SCMA codebooks, while in the uplink GAM points are directly mapped to user codebooks. The proposed codebooks exhibit good performance with low peak to average power ratio (PAPR) compared to the codebooks proposed in the literature based on constellation rotation and interleaving. Index Terms-Sparse code multiple access, codebook design, golden angle modulation, mapping, PAPR reduction. NOMA techniques can be classed under three categories: power-domain NOMA (PD-NOMA) [1], code-domain NOMA (CD-NOMA) [2], [3], [4] and a combination of PD-NOMA and CD-NOMA called power domain sparse code multiple access [5]. Low-density signature (LDS) [2], [3] is an efficient CD-NOMA that allows operating at overloaded conditions with performance close to single user case with affordable complexity. Due to the low-density property of signatures, only few users will use the same resource in order to reduce the interference and the data symbol for each user will be spread on a few number of resources. Like low-density parity-check coding, the low-density characteristic of LDS signatures allows to use the message passing algorithm (MPA) for multiuser

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