Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: MIMO Architectures for Efficient Communication in Space   The characteristics of a space-to-space multiple-input, multiple-output
(MIMO) communication channel that distinguish it from terrestrial MIMO
communication channels are summarized and discussed primarily from an
information-theoretic viewpoint. The implications of these characteristics for
the design and application of future space-based communication systems are also
discussed, and it is shown that in general, either energy-efficient or
spectrally-efficient communication in space can only be achieved using a
distributed MIMO architecture.

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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
3
The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat