Enhanced Contention Resolution Diversity Slotted ALOHA in Satellite-Based IoTs Using Sparse Code Multiple Access

As a efficient random access scheme, contention resolution diversity slotted ALOHA (CRDSA) improves the system throughput greatly, although deadlock problem limits the maximum throughput of system. To address this issue, in this paper, a non-orthogonal multiple access (NOMA) technique is proposed with random access (RA) scheme for supporting multiple terminals access in satellite IoT-oriented networks, by utilizing a code domain NOMA called Sparse Code Multiple Access (SCMA). In the proposed scheme, the throughput is mainly improved by physical (PHY) decoding and iterative decoding. Through mathematical analysis, the throughput lower bound of our scheme is shown and the simulated result proves the proposed scheme is efficient in enhancing RA throughput.