Page 50 - ITU Journal Future and evolving technologies – Volume 2 (2021), Issue 2

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

massive Machine Type Communications (mMTC) Analysis of research articles [12, 13 and the
that increases connection reliability for different references therein] and Internet communications
smart devices of the Internet of Things (IoT). referred to the latest developments in the field of
5G NR allows us to conclude that for today, world
At present, the main interest of a 5G NR network’s
operators and users is focused on the first point in equipment manufacturers have fully mastered the
order to provide super-high-speed transmission of FR1 compatible with 4G LTE and partially the FR2,
a huge amount of information. Following this need, mainly in its lower sub-band. In its upper part of far
unlike previous generations of cellular beyond 40 GHz, the network and user equipment
has received the greatest development, providing
communications, the standard frequency
allocation of the 5G NR wireless fronthaul is wireless communications only with fixed network
divided into two sub-bands: Frequency Range 1 users. The implementation by mobile network
(FR1) in the 1-6 GHz [7] and Frequency Range 2 users of the all allocated MMW band and
(FR2) in the 24-71 GHz [8]. The rest of the service prospective operating RFs up to and over 100 GHz
scenarios have their own, different from each using all three of the above service scenarios is
other, requirements to the accommodating considered as the crucial task for wireless
networks, and the Mobile Fronthaul (MFH) and/or fronthaul of 6th generation (6G).
Mobile Backhaul (MBH) should be optimized for A detailed study of existing approaches to the
their implementation [9]. optimal configurations of B5G networks and our
experience in researching the optimal principles
As for a MFH design principle, centralized radio
access network (C-RAN) architecture has been for designing analog fronthaul networks with the
already introduced in 4G LTE systems, in which distribution of RF signals in the MMW band [16-21]
multiple Remote Radio Heads (RRHs) at antenna suggest that for an NG-RAN, the optimal approach
sites are connected to a single Base Band Unit (BBU) would be to use A-RoF as an architectural concept
located at a central office so as to enable coordinated and MWP as a technological concept for designing
control of the multiple RRHs using the Common an RU containing both optoelectronic and
Public Radio Interface (CPRI) technical standard. microwave-electronic (MWE) elements. However,
However, there is a great issue referred to the link the developer of new MWE devices including MWP
speed for CPRI, which is more than 10 times larger units is facing a problem of choosing an
appropriate computer platform for their modeling
than that of the mobile user data rate mainly due to
the quantization process of the radio frequency (RF) and design. In particular, an RU designer is forced
signal waveform, especially of millimeter waves to use means of several computer-aided design
(MMW). Since the maximum user data rate in 5G (CAD) tools because the existing optical and
systems is assumed to be 20 Gbps [10], this interface optoelectronic CAD tools (OE-CAD) are not as
seems to be unsustainable in 5G NR systems in their developed as compared with the CAD tools
current form. To solve this problem, a so-called intended for the modeling of microwave-
functional split of the BS configuration was recently electronics devices (ME-CAD) [22]. For example,
standardized into the next generation RAN (NG-RAN) well-known OE-CAD tool VPI Photonics Design
with the introduction of newer functional blocks, Suite (PDS) allows executing in precision manner
such as a Central Unit (CU), a Distributed Unit (DU), the modeling of a fiber-optic link with detailed
study of optical units’ performances, but RF and
and a Radio Unit (RU) instead of a BBU and RRH [11-
13]. especially microwave and millimeter-wave
functional units are represented in an idealized
To design optimally NG-RANs using analog Radio- manner, without paying attention to the specialties
over-Fiber (A-RoF) architecture, two options of the microwave band. On the other hand,
including Radio Frequency-over-Fiber (RFoF) and operating at a symbolic level modern high-power
its derivative Intermediate Frequency-over-Fiber microwave ME-CAD tool Cadence AWRDE simply
(IFoF) transmission architectures are considered and with high precision solves this problem but
as promising candidates [14]. In addition, the there are completely no models of active
microwave-photonics (MWP) technology [15] is optoelectronic components in its library. To fill this
promising for designing the equipment for the RUs gap, we have developed by AWRDE and validated
of the millimeter and sub-millimeter ranges, in experimentally a number of the models for active
which the updated 5G and new beyond 5G (B5G) and passive MWP elements, such as semiconductor
MFH networks will operate. laser, p-i-n photodetector, two types of optical

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