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.
Highlights
O NE of the challenges in the 5th and beyond-5th generation wireless communication systems is the requirement for very high data transmission rates [1,2]
Symbols which will be transmitted to different users are multiplexed by the use of superposition coding at the base station (BS)
Appendix B in [11] further proves that the bounded pairwise error probability (PEP) may correspond to the assumption that at high signal-to-noise ratio (SNR) only one QAM symbol in a Golden codeword pair is detected with errors, while the other QAM symbol in the Golden codeword pair is detected correctly
Summary
O NE of the challenges in the 5th and beyond-5th generation wireless communication systems is the requirement for very high data transmission rates [1,2]. Multiplexing may be implemented in orthogonal multiple access (OMA) wireless communication systems. In OMA wireless communication systems, multiple users are assigned different radio resources, for example, frequency or time. Extensive research has been focused on another technique to improve data transmission rate, non-orthogonal multiple access (NOMA). In DL-NOMA systems, all mobile users share the same radio resources. In UL-NOMA systems, all users share the same time-frequency resources to transmit their signals to the BS. Similar to the conventional wireless communication systems, reducing signal detection complexity and improving error performance for different users are two of the research areas in NOMA systems.
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