Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hybrid Beamforming for Intelligent Reflecting Surface Aided Millimeter
  Wave MIMO Systems   As communication systems that employ millimeter wave (mmWave) frequency bands
must use large antenna arrays to overcome the severe propagation loss of mmWave
signals, hybrid beamforming has been considered as an integral component of
mmWave communications. Recently, intelligent reflecting surface (IRS) has been
proposed as an innovative technology that can significantly improve the
performance of mmWave communication systems through the use of low-cost passive
reflecting elements. In this paper, we study IRS-aided mmWave multiple-input
multiple-output (MIMO) systems with hybrid beamforming architectures. We first
exploit the sparse-scattering structure and large dimension of mmWave channels
to develop the joint design of IRS reflection matrix and hybrid beamformer for
narrowband MIMO systems. Then, we generalize the proposed joint design to
broadband MIMO systems with orthogonal frequency division multiplexing (OFDM)
modulation by leveraging the angular sparsity of frequency-selective mmWave
channels. Simulation results demonstrate that the proposed joint designs can
significantly enhance the spectral efficiency of the systems of interest and
achieve superior performance over the existing designs.

25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph
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The categories of this paper are: stat