Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reconfigurable Intelligent Surface-Based Wireless Communication: Antenna
  Design, Prototyping and Experimental Results   One of the key enablers of future wireless communications is constituted by
massive multiple-input multiple-output (MIMO) systems, which can improve the
spectral efficiency by orders of magnitude. However, in existing massive MIMO
systems, conventional phased arrays are used for beamforming, which result in
excessive power consumption and hardware cost. Recently, reconfigurable
intelligent surface (RIS) has been considered as one of the revolutionary
technologies to enable energy-efficient and smart wireless communications,
which is a two-dimensional structure with a large number of passive elements.
In this paper, we propose and develop a new type of high-gain yet low-cost RIS
having 256 elements. The proposed RIS combines the functions of phase shift and
radiation together on an electromagnetic surface, where positive
intrinsic-negative (PIN) diodes are used to realize 2-bit phase shifting for
beamforming. Based on this radical design, the world's first wireless
communication prototype using RIS having 256 2-bit elements is designed and
developed. Specifically, the prototype conceived consists of modular hardware
and flexible software, including the hosts for parameter setting and data
exchange, the universal software radio peripherals (USRPs) for baseband and
radio frequency (RF) signal processing, as well as the RIS for signal
transmission and reception. Our performance evaluation confirms the feasibility
and efficiency of RISs in future wireless communications. More particularly, it
is shown that a 21.7 dBi antenna gain can be obtained by the proposed RIS at
2.3 GHz, while at the millimeter wave (mmWave) frequency, i.e., 28.5 GHz, a
19.1 dBi antenna gain can be achieved. Furthermore, the over-the-air (OTA) test
results show that the RIS-based wireless communication prototype developed is
capable of significantly reducing the power consumption.

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The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
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The categories of this paper are: eess
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc