Codeword Position Index Based Sparse Code Multiple Access System

In this letter, a novel variant of sparse code multiple access (SCMA), called codeword position index-based SCMA (CPI-SCMA), is proposed. In this scheme, the information is transmitted not only by the codewords in a M-point SCMA codebook, but also by the indices of the codeword positions in a data block. As such, both the power and transmission efficiency can be improved. Furthermore, CPI-SCMA can achieve better error rate performance compares to conventional SCMA in the region of moderate and high signal-to-noise ratios.