SCMA Codebook Design Based on Uniquely Decomposable Constellation Groups

Sparse code multiple access (SCMA), which helps improve spectrum efficiency (SE) and enhance connectivity, has been proposed as a non-orthogonal (NOMA) scheme for 5G systems. In SCMA, codebook design determines system overload ratio detection performance at receiver. this paper, an SCMA approach is based on uniquely decomposable constellation group (UDCG). We show that there are N+1 ( N ≥ 1) constellations in the UDCG, each of M (M 2) points. These allocated to users sharing same resource. Combining resources user, we can obtain UDCG-based sets. Bit error (BER) will be discussed terms coding gain maximization with superimposed codebooks. Simulation results demonstrate resource large minimum Euclidean distance (MED) meets decodable constraint. Thus, BER outperforms existing schemes both uncoded coded systems, especially large-size