A Tutorial on Decoding Techniques of Sparse Code Multiple Access

Sparse Code Multiple Access (SCMA) is a disruptive code-domain non-orthogonal multiple access (NOMA) scheme to enable future massive machine-type communication networks. As an evolved variant of code division (CDMA), users in SCMA are separated by assigning distinctive sparse codebooks (CBs). Efficient multiuser detection carried out at the receiver employing message passing algorithm (MPA) that exploits sparsity CBs achieve error performance approaching maximum likelihood receiver. In spite numerous research efforts recent years, comprehensive one-stop tutorial covering background, basic principles, and new advances, still missing, best our knowledge. To fill this gap stimulate more forthcoming research, we provide holistic introduction principles encoding, CB design, MPA based decoding self-contained manner. ambitious paper aiming push limits SCMA, present survey advanced techniques with brief algorithmic descriptions as well several promising directions.