Factor Graph Hopping Based FH-SCMA for Band-Limited and Large-Scale IoT Networks

In wireless Internet-of-Thing (IoT) networks, massive nodes/users congest in limited resource blocks (RB, i.e., time-frequency block). Sparse code division multiple access (SCMA) technology is a most potential solution for massive IoT access due to its superior resource utilization; however, the prototypical SCMA likely suffers from severe interference/jamming because of lacking reliable transmission strategies. To address this issue, a reliable SCMA based on factor-graph (FG) hopping scheme (FG based FH-SCMA) is proposed for massive connectivity and band-limited IoT in this paper. To meet the sparsity of transmitted FH-SCMA codewords, a FG hopping pattern with long-period is designed via Bernoulli chaotic map. Through the proposed system design, physical RBs utilized by SCMA codewords are randomly hopped within one RB-group so as to obtain efficient RB utilization and robust transmission; meanwhile, iteration error in message-passing-algorithm (MPA) resulted from the hopping RB-collision in the SCMA receiver can be alleviated. The numerical and simulation results show that, under the jamming attack, the proposed FH-SCMA system can attain the reliable transmission performance, compared to the traditional SCMA and previous FH-SCMA systems.