Minimum BLER NOMA Design with Finite Blocklength

Non-orthogonal multiple access (NOMA) has been considered as a promising technology for enabling massive connectivity and achieving high spectral efficiency in future wireless communication. In the literature, most of the existing NOMA schemes are designed with the assumption of infinite blocklength, which may lead to suboptimal performance in practical communication systems. Thus, this paper investigates the downlink NOMA system with finite blocklength (FBL) transmission, namely the downlink FBL-NOMA system. We focus on developing a joint resource allocation scheme from single-channel to multi-channel systems, aiming at minimizing the average block error rate (BLER) for the downlink FBL-NOMA. Specifically, for single-channel systems, the optimal rate and power allocation scheme are derived in semi-closed form. For multi-channel systems, we conduct the convexity analysis of the minimum BLER problem and provide the optimal solution in waterfilling form for convex cases, as well as an efficient majorization-minimization (MM)-based algorithm for general cases. We also propose an efficient method to jointly optimize channel assignment, rate allocation, and power allocation for multi-channel FBL-NOMA systems. Simulation results demonstrate the superiority of the proposed designs over the existing NOMA and orthogonal multiple access (OMA) schemes in terms of reliability and efficiency.