Page 99 - ITU Journal, Future and evolving technologies - Volume 1 (2020), Issue 1, Inaugural issue

ITU Journal on Future and Evolving Technologies, Volume 1 (2020), Issue 1

DESIGN AND ANALYSIS OF A RECONFIGURABLE INTELLIGENT META-SURFACE FOR VEHICULAR
NETWORKS

1
1
Mohammad Ojaroudi , Valeria Loscrí , Anna Maria Vegni 2
1 2
Inria Lille - Nord Europe, Roma Tre University, Rome, Italy
NOTE: Corresponding author: Valeria Loscrí, valeria.loscri@inria.fr

Abstract – In this work, a new paradigm for vehicular communications based on Reconfigurable Intelligent Meta-surfaces
(RIMs) is presented. By using the proposed RIM, we are able to manipulate electromagnetic waves in the half-space, since
the element is reflective. The unit cell consists of a U-shaped designed microstrip structure equipped with a pin diode and via
a hole. In this study, two different reflection modes are achieved for 1-bit data transferring in each state. By incorporating
these two different configurations together, the reflected phases in the proposed RIM surface can be controlled respectively in
∘
∘
0 and 180 . The proposed unit cell can provide a usable double negative functional characteristic around 5.3 GHz. The main
goal of this paper is the use of a multifunctional behavior RIM for vehicular communications to code the transmitted wave. A
novel phase distribution diagram is generated to propagate in each angle. Moreover, two major electromagnetic modulation
functions, beam forming and space coding have been demonstrated. Finally, we show how the RIM can be employed for
vehicular communications, acting as a coated access point along the street. We derive the instantaneous data rate at the re-
ceiver node, the outage probability and the channel capacity, as affected by different beam widths, distances and vehicle speed.

Keywords – Beam width, Instantaneous data rate, Reconfigurable meta-surfaces, V2X communications

1. INTRODUCTION of the propagating signal is not available. [22] and [23]
are among the first contributions of exploitation of RIM
In recent years, special attention has been paid to driver- in vehicular communications. In [22], the authors focus
less cars using automotive radars [7, 8]. A Vehicle-to- on the physical layer security based on the exploitation of
Everything (V2X) communication paradigm has emerged a RIM or RIS (Reconfigurable Intelligent Surface). They
as one of the most important enabling technologies for derive the average secrecy capacity of the system, by con-
vehicular networks. This has the potential of making sidering an ideal reconfigurable meta-surface. They do
streets and highways safer, the traffic more efficient and not give any detail about the design of a real meta-surface
less harmful to the environment [9]. An example is the with the needed characteristics in order to obtain the spe-
exchange of traffic information, as in the Self-Organizing cific behavior as described in the paper. Also in [23], the
Traffic Information System approach [12]. authors show the rich potentiality of the RIM integration
in a vehicular communication system, by analysing a hy-
One of the most important challenges arising in the V2X pothetic ideal controllable meta-surface. Anyway, no de-
paradigm is the high dynamic and the need of highly ef- tail about the features of a real meta-surface is provided in
ficient communication solutions in order to “follow” the the paper. In [17], we have proposed a unit cell configura-
rapid changing of communication nodes. Recently, an tion working at millimiter-waves in order to control the
innovative wireless communication paradigm based on phase shift from 0 to 180 . Specifically, we have investi-
∘
the utilization of specific features of controllable meta- gated the unit cell design without evaluating the full struc-
surfaces has been investigated in [2, 3, 4, 5, 6, 15]. With ture and relate the capability to control the beam width
the advancement of technology in metamaterials, meta- based on the number of the unit cells of the full structure.
surfaces which are a thin two-dimensional structure of Indeed, the higher is the number of the unit cells of the full
metamaterials [1], due to their unique properties like the structure, the better is the capacity to control the beam
capability to provide abrupt phase shift, amplitude modu-
width of the radiation pattern generated as the reflected
lation, and polarization conversion of the electromagnetic
wave of an impinging signal.
(EM) wave, have found a variety of applications in various
fields of science, such as physics, engineering, biotechnol- As demonstrated in [11], it is possible to accurately model
ogy, and telecommunications [18]. the number of cells as sources of secondary radiation [16]
by applying the Huygens principle in the far-field limit. In
Reconfigurable Intelligent Meta-surfaces (RIMs) can be practice, the higher is the number of unit cells weconsider
very effective for improving the performance of a V2X in the full structure, the better is the capability to control
communication system, especially when the Line-of-Sight the phase, but above all to control the beam width of the

© International Telecommunication Union, 2020 79