Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Capacity Approaching Low Density Spreading in Uplink NOMA via Asymptotic
  Analysis   Low-density spreading non-orthogonal multiple-access (LDS-NOMA) is considered
where $K$ single-antenna user-equipments (UEs) communicate with a base-station
(BS) over $F$ fading sub-carriers. Each UE $k$ spreads its data symbols over
$d_k<F$ sub-carriers. We aim to identify the LDS-code allocations that maximize
the ergodic mutual information (EMI). The BS assigns resources solely based on
pathlosses. Conducting analysis in the regime where $F$, $K$, and ${d_k,\forall
k}$ converge to $+\infty$ at the same rate, we present EMI as a deterministic
equivalent plus a residual term. The deterministic equivalent is a function of
pathlosses and spreading codes, and the small residual term scales as
$\mathcal{O}(\frac{1}{\min(d_k^2)})$. We formulate an optimization problem to
get the set of all spreading codes, irrespective of sparsity constraints, which
maximize the deterministic EMI. This yields a simple resource allocation rule
that facilitates the construction of desired LDS-codes via an efficient
partitioning algorithm. The acquired LDS-codes additionally harness the small
incremental gain inherent in the residual term, and thus, attain near-optimal
values of EMI in the finite regime. While regular LDS-NOMA is found to be
asymptotically optimal in symmetric models, an irregular spreading arises in
generic asymmetric cases. The spectral efficiency enhancement relative to
regular and random spreading is validated numerically.

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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: astro-ph
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an