Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Novel Power Allocation Scheme for Two-User GMAC with Finite Input
  Constellations   Constellation Constrained (CC) capacity regions of two-user Gaussian Multiple
Access Channels (GMAC) have been recently reported, wherein an appropriate
angle of rotation between the constellations of the two users is shown to
enlarge the CC capacity region. We refer to such a scheme as the Constellation
Rotation (CR) scheme. In this paper, we propose a novel scheme called the
Constellation Power Allocation (CPA) scheme, wherein the instantaneous transmit
power of the two users are varied by maintaining their average power
constraints. We show that the CPA scheme offers CC sum capacities equal (at low
SNR values) or close (at high SNR values) to those offered by the CR scheme
with reduced decoding complexity for QAM constellations. We study the
robustness of the CPA scheme for random phase offsets in the channel and
unequal average power constraints for the two users. With random phase offsets
in the channel, we show that the CC sum capacity offered by the CPA scheme is
more than the CR scheme at high SNR values. With unequal average power
constraints, we show that the CPA scheme provides maximum gain when the power
levels are close, and the advantage diminishes with the increase in the power
difference.

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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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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: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an