Abstract
In this work, we address the problem of finding globally optimal power allocation strategies to maximize the users sum-rate (SR) as well as system energy efficiency (EE) in the downlink of single-cell multicarrier non-orthogonal multiple access (MC-NOMA) systems. Each NOMA cluster includes a set of users in which the well-known superposition coding (SC) combined with successive interference cancellation (SIC) technique is applied among them. By obtaining the closed-form expression of intra-cluster power allocation, we show that MC-NOMA can be equivalently transformed to a virtual orthogonal multiple access (OMA) system, where the effective channel gain of these virtual OMA users is obtained in closed-form. Then, the SR and EE maximization problems are solved by using very fast water-filling and Dinkelbach algorithms, respectively. The equivalent transformation of MC-NOMA to the virtual OMA system brings new theoretical insights, which are discussed throughout the paper. The extensions of our analysis to other scenarios, such as considering users rate fairness, admission control, long-term performance, and a number of future next-generation multiple access (NGMA) schemes enabling recent advanced technologies, e.g., reconfigurable intelligent surfaces are discussed. Extensive numerical results are provided to show the performance gaps between single-carrier NOMA (SC-NOMA), OMA-NOMA, and OMA.
Highlights
In addition to the superior spectral efficiency of non-orthogonal multiple access (NOMA) compared to orthogonal multiple access (OMA), i.e., frequency division multiple access (FDMA), and time division multiple access (TDMA) [4], [5], academic and industrial research has demonstrated that NOMA can support massive connectivity, which is important for ensuring that the fifth generation (5G) wireless networks can effectively support Internet of Things (IoT) functionalities [9], [10]
We address the problem of finding optimal power allocation for maximizing SR/EE of the downlink single-cell Hybrid-NOMA system including multiple clusters each having an arbitrary number of multiplexed users
We addressed the problem of finding globally optimal power allocation algorithms to minimize the BSs power consumption, and maximize SR/EE of the general multiuser downlink single-cell Hybrid-NOMA systems
Summary
T HE rapidly growing demands for high data rate services along with energy constrained networks necessitate the characterization and analysis of the next-generation multiple access (NGMA) techniques in wireless communication systems. The SC-SIC technique is called non-orthogonal multiple access (NOMA) [6]. We consider powerdomain NOMA, and subsequently, the term NOMA is referred to as power-domain NOMA. In [18], it is shown that the capacity region of the multiuser downlink RIS system can be achieved by NOMA with time sharing. To this end, NOMA is a promising candidate solution for the beyond-5G (B5G)/sixth generation (6G) wireless networks [19]
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