Multi-Node Confirmation Mechanism Based on PC-SCMA Superposition Transmission Systems

Sparse code multiple access (SCMA) can enable multiple nodes to share the same time-frequency resources, thereby effectively alleviating the problem of insufficient spectrum resource caused by multi-node access. It is a promising technology for realizing massive machine-type communication (mMTC). Aiming at the problem of large latency caused by successive replies in the traditional acknowledgment (ACK) mechanism, this paper proposes a multi-node-oriented reply mechanism, which allows single ACK frame to carry the address fields of multiple nodes to ensure real-time reply to nodes. Simulation results in the polar code SCMA (PC-SCMA) systems with hybrid automatic repeat request (HARQ) assistance show that with the proposed reply mechanism-based HARQ assistance, the block error rate (BLER) of the PC-SCMA system is less than $10\wedge(-4)$ when the Eb/N0 is 4.5 dB and the system latency can be reduced by up to 15.36%.