Non-orthogonal multiple access (NOMA) is a promising multiple access technique for 5G wireless technology. In this paper, we first discuss the fundamentals of uplink and downlink NOMA transmissions in a cellular system and outline their key distinctions in terms of implementation complexity, detection and decoding at the SIC receiver(s), and the intra-cell and inter-cell interferences. Later, for both downlink and uplink NOMA, for each individual user in a two-user NOMA cluster, we theoretically derive the NOMA dominant condition, which refers to the condition under which the spectral efficiency gains of NOMA are guaranteed compared to conventional orthogonal multiple access (OMA). The conditions, which are distinct for uplink and downlink as well as for each individual user, provide direct insights into selecting appropriate users in two-user NOMA clusters. Numerical results show the significance of the derived conditions for user selection in uplink/downlink NOMA clusters and provide a comparison to the random user selection. Finally, a brief summary of the recent research investigations is provided which is followed by a discussion on the research challenges and future research directions.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Uplink Vs. Downlink NOMA in Cellular Networks: Challenges and Research Directions


    Contributors:


    Publication date :

    2017-06-01


    Size :

    1186899 byte




    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



    Intelligent Reflecting Surface Joint Uplink-Downlink Optimization for NOMA Network

    Samy, Mostafa / Abo-Zahhad, Mohammed / Muta, Osamu et al. | IEEE | 2022


    Performance Analysis of a Hybrid Downlink-Uplink Cooperative NOMA Scheme

    Wei, Zhiqiang / Dai, Linglong / Ng, Derrick Wing Kwan et al. | IEEE | 2017


    Uplink Performance Analysis of Grant-Free NOMA Networks

    Zhengy, Canjian / Zhengy, Fu-Chun / Luoy, Jingjing et al. | IEEE | 2022


    Performance Analysis of Ambient Backscatter Uplink NOMA Networks

    Chrysologou, Athanasios P. / Chatzidiamantis, Nestor D. / Boulogeorgos, Alexandros-Apostolos A. et al. | IEEE | 2023


    Capacity Characterization of Uplink NOMA in Multi-UAV Networks

    Ernest, Tan Zheng Hui / Madhukumar, A S / Sirigina, Rajendra Prasad et al. | IEEE | 2020