Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral Efficiency and Energy Efficiency of OFDM Systems: Impact of
  Power Amplifiers and Countermeasures   In wireless communication systems, the nonlinear effect and inefficiency of
power amplifier (PA) have posed practical challenges for system designs to
achieve high spectral efficiency (SE) and energy efficiency (EE). In this
paper, we analyze the impact of PA on the SE-EE tradeoff of orthogonal
frequency division multiplex (OFDM) systems. An ideal PA that is always linear
and incurs no additional power consumption can be shown to yield a decreasing
convex function in the SE-EE tradeoff. In contrast, we show that a practical PA
has an SE-EE tradeoff that has a turning point and decreases sharply after its
maximum EE point. In other words, the Pareto-optimal tradeoff boundary of the
SE-EE curve is very narrow. A wide range of SE-EE tradeoff, however, is desired
for future wireless communications that have dynamic demand depending on the
traffic loads, channel conditions, and system applications, e.g.,
high-SE-with-low-EE for rate-limited systems and high-EE-with-low-SE for
energy-limited systems. For the SE-EE tradeoff improvement, we propose a PA
switching (PAS) technique. In a PAS transmitter, one or more PAs are switched
on intermittently to maximize the EE and deliver an overall required SE. As a
consequence, a high EE over a wide range SE can be achieved, which is verified
by numerical evaluations: with 15% SE reduction for low SE demand, the PAS
between a low power PA and a high power PA can improve EE by 323%, while a
single high power PA transmitter improves EE by only 68%.

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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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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: cmp-lg
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The categories of this paper are: bayes-an