Page 95 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 6 – Wireless communication systems in beyond 5G era

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 6

MASSIVE DISTRIBUTED IRS AIDED WIRELESS COMMUNICATION WITH ON/OFF SELECTION
Riku Ohmiya , Tomoki Murakami , Masaaki Nishino , Yoghitha Ramamoorthi , Masashi Iwabuchi ,
2
1
1
1
1
1
Tomoaki Ogawa and Yasushi Takatori
1
1 NTT Access Network Service Systems Laboratories 1-1 Hikarinooka, Yokosuka-shi, Kanagawa, 239-0847 Japan,
2 NTT Communication Science Laboratories 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto, 619-0237 Japan.
NOTE: Corresponding author: Riku Ohmiya, riku.oomiya.ez@hco.ntt.co.jp

Abstract – The mobile communication system beyond fifth-generation (beyond 5G) is required to maintain
higher transmission capacity and reliability than existing 5G systems. To meet these requirements, one
promising solution is to incorporate an Intelligent Reflecting Surface (IRS). The IRS involves reconfiguring
the wireless propagation environment and exploiting the radio resources, not only in the conventional
frequency and time domains but also in the spatial domain by controlling the reflection amplitude and phase
of the incident electromagnetic signal. However, increased deployment of IRSs brings about interference
and greater complexity. Therefore, in this paper, we propose an ON/OFF IRS selection method on massive
IRS aided wireless communications that can simultaneously achieve interference suppression and capacity
improvement. In addition, the proposed method reduces operational complexity using a simple 1-bit control.
The results of computer simulation and experiment show that the proposed method can improve the desired
channel capacity beyond directly Single-Input Single-Output (SISO) communication without IRS while
maintaining the interference level of an interfered receiver below a certain threshold.
Keywords – Channel capacity, clustering methods, intelligent reflecting surface (IRS), interference,
optimization

1. INTRODUCTION resources, it is important to avoid Non Line-Of-Sight
(NLOS) signals and constructively use multipath
Mobile communication traffic continues to increase signals [2]. However, from the perspective of
due to the expanded use of smart devices such as system operation, there are concerns that
smartphones and tablets. According to the increasing the number of propagation paths would
International Telecommunication Union require the installation of a large number of base
Radiocommunication Sector (ITU-R) [1], worldwide stations and antennas, which increases the cost of
mobile traffic is increasing at an annual rate of 1.5 infrastructure.
and is expected to exceed 5,000 exabytes (EB) per
month by 2030. Expansion of the transmission Against this background, research and development
capacity of today’s mobile network is, therefore, an have recently begun on new technology for
important issue going forward. As of February 2021, controlling the propagation path itself using a
commercialization of the fifth-generation mobile reflecting device called an Intelligent Reflecting
communications system (5G) has begun in several Surface (IRS) [3]. A reflector incorporating the IRS
countries, but discussions on the beyond fifth- transforms into an active reflector having reflection
generation (beyond 5G), the new mobile network characteristics different from those of an ordinary
planned for 2030, are proceeding in parallel. object. It can control the phase and amplitude of the
Specifically, there is a need to achieve an ultra-high- incident radio-wave enable or disable reflection,
transmission-capacity and ultra-high-reliability control its direction, etc., without having to perform
mobile network in beyond 5G at levels higher than complex signal processing. If multiple distributed
that of 5G. This requirement is driving a transition IRS reflectors can be deployed and their operation
to multifaceted research and development [2]. controlled in a coordinated manner, it should be
possible to make maximum use of radio resources
To meet the complex requirements of the radio not only in the frequency and time domains as usual
layer in beyond 5G, it is essential that radio but also in the spatial domain.
resources can be exploited not only through
technical innovations in the frequency and time A number of studies have been conducted on IRS
domains as has been pursued up to now but also in reflector-aided wireless communication [3-9]. The
the spatial domain. To utilize all the available radio study by Basar et al. [3] advances the concept of

© International Telecommunication Union, 2021 83