Practical Decoding Scheme for Doubly Irregular Sparse Code Multiple Access

Abstract

Doubly irregular sparse code multiple access (DI-SCMA) is a type of sparse code multiple access (SCMA) with irregular degree distributions both in resource node (RN) and user node (UN) to increase the overloading factor. This paper proposes a practical decoding scheme for DI-SCMA having low computational complexity based on using peeling decoding algorithm. We also use mother constellation capable of detecting 4 users simultaneously based on binary shift keying (BPSK)-like mapping leading to a total constellation similar to the 8 phase shift keying (8-PSK). We evaluate the decoding behaviour of the proposed DI-SCMA using extrinsic information transfer (EXIT) chart and computer simulations. Our results confirm the validity of achievable overloading factor using the practical decoding technique with better bit error rate (BER) performances compared to performances of 8-PSK modulations.