Uplink Non-Orthogonal Multiple Access With Golden Codeword Constellation

Abstract

Non-orthogonal multiple access (NOMA) is a technique to improve spectral efficiency. In uplink NOMA (UL-NOMA) systems, mobile multiusers are globally synchronized to share the same time and frequency resources, and transmit their own independent symbols to the base station (BS). This paper proposes an UL-NOMA system with Golden codeword constellation (GCC). In the proposed UL-NOMA system, two users, the center user and the edge user, transmit their own independent Golden codewords to the BS. Compared to the conventional UL-NOMA systems, the proposed UL-NOMA system not only preserves the spectral efficiency, but also improves error performance. The fast essentially maximum likelihood (FE-ML) detection with dynamic signal detection subset (DSDS) is proposed to decode the Golden codewords. A lower bound on error performance for both the center user and edge user is further derived. Simulation results show that the derived lower bound well predicts the error performance of UL-NOMA with GCC. Simulation results also show that the proposed UL-NOMA system outperforms the conventional UL-NOMA system by at least 2 dB signal-to-noise ratio (SNR) for both the center user and edge user at a bit error rate of $2 \times 10^{-5}$ . Finally, both complexity analysis and simulation results show that the proposed FE-ML with DSDS result in a 68% complexity reduction compared to the FE-ML with SDS at an SNR of 23 dB for the center user transmitting 64QAM and the edge user transmitting 16QAM.