Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orthogonal vs Non-Orthogonal Multiple Access with Finite Input Alphabet
  and Finite Bandwidth   For a two-user Gaussian multiple access channel (GMAC), frequency division
multiple access (FDMA), a well known orthogonal-multiple-access (O-MA) scheme
has been preferred to non-orthogonal-multiple-access (NO-MA) schemes since FDMA
can achieve the sum-capacity of the channel with only single-user decoding
complexity [\emph{Chapter 14, Elements of Information Theory by Cover and
Thomas}]. However, with finite alphabets, in this paper, we show that NO-MA is
better than O-MA for a two-user GMAC. We plot the constellation constrained
(CC) capacity regions of a two-user GMAC with FDMA and time division multiple
access (TDMA) and compare them with the CC capacity regions with trellis coded
multiple access (TCMA), a recently introduced NO-MA scheme. Unlike the Gaussian
alphabets case, it is shown that the CC capacity region with FDMA is strictly
contained inside the CC capacity region with TCMA. In particular, for a given
bandwidth, the gap between the CC capacity regions with TCMA and FDMA is shown
to increase with the increase in the average power constraint. Also, for a
given power constraint, the gap between the CC capacity regions with TCMA and
FDMA is shown to decrease with the increase in the bandwidth. Hence, for finite
alphabets, a NO-MA scheme such as TCMA is better than the well known O-MAC
schemes, FDMA and TDMA which makes NO-MA schemes worth pursuing in practice for
a two-user GMAC.

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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ex