Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamic User Clustering and Power Allocation for Uplink and Downlink
  Non-Orthogonal Multiple Access (NOMA) Systems   In this paper, first we briefly describe the differences in the working
principles of uplink and downlink NOMA transmissions. Then, for both uplink and
downlink NOMA, 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 cluster(s) 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 (MINLP) 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 a NOMA cluster and group 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 KKT 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 performance of NOMA over orthogonal multiple access (OMA) and illustrate
the significance of NOMA in various network scenarios.

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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an