Max-Min Fairness with Selection Combining Strategy on Cooperative NOMA: A Finite Blocklength Analysis

Abstract

In this paper, the performance of a cooperative relaying technique in a non-orthogonal multiple access (NOMA) system is considered in short packet communications with finite blocklength (FBL) codes. We examine the performance of a decode-and-forward (DF) relaying along with selection combining (SC) strategy at the receiver. Our goal is optimal power and blocklength allocation to attain maximum users' fair throughput in a downlink NOMA (DL-NOMA) system with two users, where the user with a stronger channel (strong user) acts as a relay for the user with a weaker channel (weak user). For this purpose, an optimization problem is formulated and an analytical solution is proposed. Numerical results show that the proposed Cooperative NOMA scheme improves the users' fair throughput in comparison with the NOMA in the FBL regime.