An Optimization Method to Maximize the Service Quality of SCMA Grant-Free Access with MPR

Grant-free access successfully reduces the overhead and delay of signaling in the scenario of ultra-reliable low-latency communications (URLLC). However, it is also prone to conflict in the case of high load, resulting the lose of spectrum efficiency, reduced reliability and increased delay. In this paper, we realize K-multipacket reception (K-MPR) with sparse code multiple access (SCMA) technology to improve spectrum efficiency and throughput, and yet its implementation greatly increases the difficulty of ensuring the reliability of data transmission. Therefore, we propose an optimization method to maximize service quality of SCMA grant-free access with MPR. First, we investigate the behaviors of transient system via Markov chain to obtain reliability under delay constraints. Furthermore, we use dichotomy to calculate the minimum MPR ability value
$K$
. The simulation results show the validity of theoretical analysis. The proposed scheme maintains the increasing trend of reliability under delay constraints and tradeoff between throughput and reliability under delay constraints is presented, while optimal tradeoff between spectrum efficiency and reliability is achieved.