Dynamic User Clustering and Power Allocation for Uplink and Downlink Non-Orthogonal Multiple Access (NOMA) Systems
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This paper proposes a low-complexity sub-optimal user grouping scheme that exploits the channel gain differences among users in an NOMA cluster and groups them into a single cluster or multiple clusters in order to enhance the sum-throughput of the system.Abstract:
Non-orthogonal multiple access (NOMA) has recently been considered as a key enabling technique for 5G cellular systems. In NOMA, by exploiting the channel gain differences, multiple users are multiplexed into transmission power domain and then non-orthogonally scheduled for transmission on the same spectrum resources. Successive interference cancellation (SIC) is then applied at the receivers to decode the message signals. In this paper, first, we briefly describe the differences in the working principles of uplink and downlink NOMA transmissions in a cellular wireless system. Then, for both uplink and downlink NOMAs, we formulate a sum-throughput maximization problem in a cell such that the user clustering (i.e., grouping users into a single cluster or multiple clusters) and power allocations in NOMA clusters can be optimized under transmission power constraints, minimum rate requirements of the users, and SIC constraints. Due to the combinatorial nature of the formulated mixed integer non-linear programming problem, we solve the problem in two steps, i.e., by first grouping users into clusters and then optimizing their respective power allocations. In particular, we propose a low-complexity sub-optimal user grouping scheme. The proposed scheme exploits the channel gain differences among users in an NOMA cluster and groups them into a single cluster or multiple clusters in order to enhance the sum-throughput of the system. For a given set of NOMA clusters, we then derive the optimal power allocation policy that maximizes the sum-throughput per NOMA cluster and in turn maximizes the overall system throughput. Using Karush–Kuhn–Tucker optimality conditions, closed-form solutions for optimal power allocations are derived for any cluster size, considering both uplink and downlink NOMA systems. Numerical results compare the performances of NOMA and OMA and illustrate the significance of NOMA in various network scenarios.read more
Citations
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Journal ArticleDOI
A Survey on Non-Orthogonal Multiple Access for 5G Networks: Research Challenges and Future Trends
Zhiguo Ding,Xianfu Lei,George K. Karagiannidis,Robert Schober,Jinhong Yuan,Vijay K. Bhargava +5 more
TL;DR: In this paper, the authors provide an overview of the latest NOMA research and innovations as well as their applications in 5G wireless networks and discuss future challenges and future research challenges.
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A Survey on Non-Orthogonal Multiple Access for 5G Networks: Research Challenges and Future Trends
Zhiguo Ding,Xianfu Lei,George K. Karagiannidis,Robert Schober,Jinhong Yuan,Vijay K. Bhargava +5 more
TL;DR: In this paper, the authors provide an overview of the latest NOMA research and innovations as well as their applications in 5G wireless networks and discuss future research challenges regarding 5G and beyond.
Journal ArticleDOI
Nonorthogonal Multiple Access for 5G and Beyond
TL;DR: This work provides a comprehensive overview of the state of the art in power-domain multiplexing-aided NOMA, with a focus on the theoretical N OMA principles, multiple-antenna- aided NomA design, and on the interplay between NOMa and cooperative transmission.
Journal ArticleDOI
A Survey of Non-Orthogonal Multiple Access for 5G
TL;DR: A comprehensive survey of the original birth, the most recent development, and the future research directions of non-orthogonal multiple access, along with a range of challenging open problems that should be solved for NOMA.
Journal ArticleDOI
Non-Orthogonal Multiple Access (NOMA) for Downlink Multiuser MIMO Systems: User Clustering, Beamforming, and Power Allocation
TL;DR: In this paper, the authors investigated the application of NOMA with successive interference cancellation (SIC) in downlink multiuser multiple-input multiple-output (MIMO) cellular systems, where the total number of receive antennas at user equipment (UE) ends in a cell is more than the number of transmit antennas at the BS.
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Non-Orthogonal Multiple Access (NOMA) for Cellular Future Radio Access
TL;DR: It is shown that the downlink NOMA with SIC improves both the capacity and cell-edge user throughput performance irrespective of the availability of the frequency-selective channel quality indicator (CQI) on the base station side.
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On the Performance of Non-Orthogonal Multiple Access in 5G Systems with Randomly Deployed Users
TL;DR: In this letter, the performance of non-orthogonal multiple access (NOMA) is investigated in a cellular downlink scenario with randomly deployed users and developed analytical results show that NOMA can achieve superior performance in terms of ergodic sum rates; however, the outage performance of N OMA depends critically on the choices of the users' targeted data rates and allocated power.
Journal ArticleDOI
Impact of User Pairing on 5G Nonorthogonal Multiple-Access Downlink Transmissions
TL;DR: Both analytical and numerical results are provided to demonstrate that F-NOMA can offer a larger sum rate than orthogonal MA, and the performance gain of F- NOMA over conventional MA can be further enlarged by selecting users whose channel conditions are more distinctive.
Journal ArticleDOI
Cooperative Non-Orthogonal Multiple Access in 5G Systems
TL;DR: In this article, a cooperative NOMA scheme is proposed, where users with better channel conditions have prior information about the messages of other users, and an approach based on user pairing is also proposed to reduce system complexity.