Sparse Code Multiple Access Codebook Design using Equiangular Tight Frames

Sparse Code Multiple Access (SCMA) is considered to be one of the potential non-orthogonal multiple access (NOMA) techniques mainly targeting uplink transmission to support massive connectivity. In this work, an efficient high dimensional uplink SCMA codebook design is proposed using the Equiangular Tight Frames. Codebook design problem is posed as construction of generalized Equiangular Tight Frames where mutual coherence among codewords are minimized toward the optimal bound. The minimization problem is handled using gradientbased alternating projection technique under average symbol energy constraint. An important feature of the proposed design is monotonically improved Bit Error Rate (BER) performance with scaling of the proposed codebook.