Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Millimeter Wave Massive MIMO Downlink Per-Group Communications with
  Hybrid Linear Precoding   We address the problem of analyzing and classifying in groups the downlink
channel environment in a millimeter-wavelength cell, accounting for path loss,
multipath fading, and User Equipment (UE) blocking, by employing a hybrid
propagation and multipath fading model, thus using accurate inter-group
interference modeling. The base station (BS) employs a large Uniform Planar
Array (UPA) to facilitate massive Multiple-Input, Multiple-Output (MIMO)
communications with high efficiency. UEs are equipped with a single antenna and
are distributed uniformly within the cell. The key problem is analyzing and
defining groups toward precoding. Because equitable type of throughput is
desired between groups, Combined Frequency and Spatial Division and
Multiplexing (CFSDM) prevails as necessary. We show that by employing three
subcarrier frequencies, the UEs can be efficiently separated into high
throughput groups, with each group employing Virtual Channel Model Beams (VCMB)
based inner precoding, followed by efficient Multi-User Multiple-Input
Multiple-Output (MU-MIMO) outer precoders. For each group, we study three
different sub-grouping methods offering different advantages. We show that the
improvement offered by Zero-Forcing Per-Group Precoding (ZF-PGP) over
Zero-Forcing Precoding (ZFP) is very high.

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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
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The categories of this paper are: nlin
10
The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
3
The categories of this paper are: physics
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: adap-org