A Novel Joint Coding Scheme for Downlink Non-orthogonal Multiple Access (NOMA)

Non-orthogonal multiple access (NOMA) is a promlsmg candidate for future 5G multiple access. Particularly NOMA uses power domain for multiple access and successive interference canceler (SIC) algorithm for multi-user detection (MUD). Different from the current downlink transmission scheme for NOMA, a novel joint coding scheme is proposed in this paper and corresponding improved SIC algorithms: zigzag SIC and iterative SIC are designed at the receiver side. Both zigzag SIC and iterative SIC algorithms are based on the novel offset frame structure. The goal is to take advantage of time domain diversity gain and certain long code gain of joint coding and advanced receiver to improve system performance without introduce additional degree of freedom. Practical considerations of NOMA, such as power allocation ratio, SIC, error propagation and channel fading are discussed. Simulation results show the proposed iterative SIC receiver and zigzag SIC receiver can both provide a better performance than conventional SIC receiver, so that the proposed joint coding scheme has obvious advantage over conventional NOMA.