Performance Analysis of Fountain Coded Non-Orthogonal Multiple Access With Finite Blocklength

Abstract

Driven by the increasing demand for high reliability and low latency, finite blocklength communications have recently become the focus of the communication research field. In this letter, to achieve high reliability and low latency communication, we propose the cross-layer design of fountain coded two-user non-orthogonal multiple access (NOMA) system with finite blocklength. Specifically, the message for each user is firstly encoded by an application-layer fountain code at the base station (BS). Then, each fountain-coded packet for each user is encoded by a physical-layer channel code into a frame. Finally, the BS sends the frames to these two users by using superposition modulation. Under the reliability constraints of two users, the relationship among the application-layer code rate, the physical-layer data rate, and the optimal power allocation coefficient is derived to minimize the transmission latency. The numerical analysis and simulation results show that the message transmission latency of the proposed cross-layer scheme is much lower than that of the scheme which only adopts physical-layer channel codes in the finite blocklength NOMA system.