NTT Technical Review

February 2024 Vol. 22 No. 2
Front-line Researchers Koji Muraki, Senior Distinguished Researcher, NTT Basic Research Laboratories
Rising Researchers Shinobu Saito, Distinguished Researcher, NTT Computer and Data Science Laboratories
Feature Articles: Recent Developments in the IOWN Global Forum Latest Activities in the IOWN Global Forum Activities for Detailing the Architecture of the Open APN and Promoting Its Practical
Application
 Technical Study on IOWN for Mobile Networks
 IOWN Data Hub to Become a Reality
 DCI Architecture Promoted by the IOWN Global Forum
Global Standardization Activities Standardization Trends in IEEE 802.11be/bn
Practical Field Information about Telecommunication Technologies
 Optical Loss Prediction Tool 1.0 toward Enabling Preventive Maintenance of Optical Fiber
CablesExternal Awards/Papers Published in Technical Journals and Conference Proceedings

Front-line Researchers

First Experimental Demonstration ofa Phenomenon That Had Not Been
Verified for More Than 20 Years
Since Its Theory Was Proposed
Koji Muraki
Senior Distinguished Researcher,
NTT Basic Research Laboratories
Abstract

In the field of condensed-matter physics, it is often the case thata theory about a phenomenon is experimentally verified 20 or 30
years after it was proposed. Koji Muraki, a senior distinguishedresearcher at NTT Basic Research Laboratories, and his coresearchers were the first in the world to experimentally observea phenomenon similar to Andreev reflection, which occurs at theinterface between a superconductor and normal metal, in a material other than a superconductor. This observation was achieved
through research on a many-body effect, which is a phenomenon
by which electrons acquire the properties that an individual electron does not possess by interacting witheach other. We asked him about this achievement, research on the fractional quantum Hall effect (one ofmany-body effects) that led to this achievement, and his mindset as a researcher engaged in basic
research.
Keywords: many-body effect, quasiparticle, Andreev reflection

Exploring quantum devices with new functions
that cannot be obtained with individual electrons
by applying the fractional quantum Hall effect—Would you tell us about the research you are currently conducting?
I’m researching many-body effects and correlation
effects caused by interactions between electrons aswell as quantum-mechanical properties of electrons
such as wave nature, superposition state, and spin. By
engineering and controlling these properties of elecNTT Technical Review

Vol. 22 No. 2 Feb. 2024

trons using the heterostructure and nanostructure ofsemiconductors and atomic-layer materials, I’m
exploring quantum devices with new functions thatcannot be obtained with individual electrons.
In my previous interview (March 2021 issue), I
talked about our group experimentally demonstratingthat (i) a topological insulator, which is a material that
conducts electricity on its surface but is an insulator
inside, can be formed using a semiconductor heterostructure and (ii) by applying a voltage to the gateelectrode of the topological insulator, it can be electrically switched between a normal insulator and1

Front-line Researchers

Metal
Incoming
electroneSuperconductor

Cooper-pairformationhReflected
hole2e(a) Andreev reflection at a conventional
superconductor junction

Fractional
QH system
Incoming
quasiparticle
e/3
×2

Integer
QH system
Electron
excitatione-e/3
Reflected
quasihole(b) Andreev reflection of quasiparticles
at a fractional-integer QH junction

Fig. 1. Conceptual diagram of Andreev reflection.

topological insulator. In this interview, I’d like todiscuss many-body effects.
A many-body effect is a phenomenon by whichelectrons interact with each other and acquire theproperties that an individual electron does not possess. Typical examples are superconductivity andferromagnetism. Among many-body effects, ourresearch group focuses on a phenomenon called thefractional quantum Hall (QH) effect, in which electrons with electron charge e (< 0) try to avoid eachother in a strong magnetic field; as a result, a certain
kind of order is created—a uniform state like liquid
without the density fluctuation. Interestingly, deviation from this uniform state of electrons occurs inunits of one-third the charge on the electrons (e/3).
The convexity of the electron density is called a “quasiparticle” and the concavity is called a “quasihole,”
and they behave like particles with charges ±e/3. The
fractional QH effect has a long history; it was discovered in 1982 and its underlying theory was publishedthe following year, which were awarded the Nobel
Prize in Physics in 1998. In the early 2000s, it wastheoretically proposed that quasiparticles and quasiholes in certain states could be used for quantum
computing, since then, research to verify that proposal has been ongoing.
It was experimentally clarified that quasiparticles
in the fractional QH state have charge e/3 from measuring and analyzing the weak noise in the current. As
a fundamental technology for quantum computing
using quasiparticles, measuring the quasiparticle
interference with a minute device fabricated in theform of a ring is necessary. In 2020, a research groupin the USA reported—as a world’s first—an experiment in which they successfully conducted such
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measurement, and that report has gained much attention. Such experiments investigate the properties ofquasiparticles with charge e/3. The electrodes andlead wires connected to the measurement instruments
are normal metals, and the electrons flowing throughthem are electrons with charge e. Therefore, what
happens when a quasiparticle with charge e/3 flows
into an electrode composed of a normal metal? Twotheoretical papers published in 1998 considered sucha question. According to the theory, when two quasiparticles with charge e/3 are injected into a metal, anelectron with charge e flows into the metal, and aquasihole with charge −e/3 (> 0) is reflected back into
the injection side to conserve charge. This phenomenon is similar to the Andreev reflection (Fig. 1) that
occurs at the interface between a superconductor andnormal metal, and we succeeded in observing it witha material other than superconductors in an experiment for the first time [1]. In addition to the significance of elucidating charge conservation at the levelof quasiparticles, which are smaller than electrons,
and the elementary processes of scattering and reflection of quasiparticles, this achievement also provides
a new perspective to consider in regard to quantum
circuits using quasiparticles. That is, not only quasiparticles but also quasiholes carrying charge areflowing in a quantum circuit using quasiparticles, andthe effect of the quasiholes must also be consideredwhen discussing the presence or absence of quasiparticle interference.
I was very happy to be able to demonstrate experimentally for the first time a phenomenon that had notbeen verified for over 20 years since its theoreticalprediction. The researcher who wrote one of theabove-mentioned theoretical papers in 1998 read our2Front-line Researchers

Gate voltage 1

Input current

Gate voltage 2

Magnetic
field

Gate electrode 2

0V

20 µm
Transmitted
current

1
1/3

Gate
Gate
electrode 1 electrode 3

Gateelectrode 1

Gateelectrode 2

Gateelectrode 3

Electron density 1/3

1
Fractional QH system Depletion
Fractional charge e/3 layer
carries current.

Gateelectrode 2

Electrondensity 1

Integer QH system
Electron ecarries current.

Fractional-integer QH junction(a) False-color scanning electron micrograph of the sample(b) Fractional-integer QH junction

Fig. 2. Conceptual diagram of the experiment.

paper and sent us an email saying, “Thank you forverifying my theory.” Subsequent research has also
helped us to understand the noise and heat generated
during these scattering and reflection processes ofquasiparticles [2]. It may sound easy when I only
write about the result, but it was a long journey fromthe start of the research until we got the satisfying
result.
Investigating the properties of quasiparticles,
which have a smaller charge than electrons, requires
extremely advanced experimental techniques, andonly a handful of research groups in the world canconduct such experiments. It was also a significant
change to have people from these research groups
pay attention to our work because of this achievement. Although my role in these studies was supervising, and my main contribution was to keep asking
questions to the member leading the research, being
involved in research that gives a young researcher an
opportunity to spread their wings and be recognizedaround the world gave me a different sense of accomplishment than I ever had before.
—Could you tell us about the experiment that produced impressive results in more detail?
To investigate the properties of quasiparticles,
more-precise measurement techniques were needed.
Thus, I asked a researcher to join our group who had
similar interests as us and the necessary skills andknowledge, and he came up with an idea of thisexperiment.
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The overview of the experiment is illustrated inFig. 2. First, a magnetic field is applied perpendicular
to a two-dimensional electron system in a GaAs (gallium arsenide) semiconductor heterostructure at low
temperature. The magnetic-field strength is thenadjusted so that the entire electron system is the integer QH state with a Landau-level filling factor* of 1.
A false-color scanning electron micrograph of thesample is shown in Fig. 2(a). The red region is a fractional QH state with a Landau-level filling factor of
1/3, which is formed by applying gate voltage 1 togate electrode 1. The blue region is an integer QH
state with a Landau-level filling factor of 1, where theelectrons with charge e play the role of a normal
metal carrying current (gate electrode 3 is fixed at 0
V). The yellow regions are gate electrode 2 applied tonarrow the interface between the fractional QH andinteger QH states. The dark-gray regions are areas
where the semiconductor is etched away, and thelight-gray regions are gate electrodes not used in thisexperiment. A fine fractional-integer QH junction isformed in the center between gate electrodes 1 and 3(marked with the green circle). In a QH region, current flows in one direction along the channels at theedge of the sample (red and blue arrows), so transmitted (blue) and reflected (red) currents can be measured.
*

Landau-level filling factor: The ratio of electron density to amagnetic field (magnetic-flux density). When this value approaches an integer, an integer QH effect occurs, and when it approaches a certain fractional value (such as 1/3), a fractional QH
effect occurs.

3

Front-line Researchers

Transmitted current= input current

1.2
1.0
0.8
Input current

0.6
0.4

1/3

Transmission
1

Measurement

0.2
0
-1.5

Reflection
-1.0

-0.5

0

Reflected current/input current

Transmitted current/input current

Transmitted current> input current

1.0

Input current

0.8
0.6
0.4

Measurement

1/3

Transmission
1

Reflection

0.2
0
-0.2
-0.4
-1.5

Reflected
current = 0

Reflected current < 0
-1.0

-0.5

Gate voltage 2 (V)Gate voltage 2 (V)(a) Transmitted current(b) Reflected current

0Fig. 3. Measurement results when the fractional-integer QH junction is narrowed by applying gate voltage 2.

Figure 2(b) shows a conceptual diagram of thefractional-integer QH junction, namely, the region
marked with the green circle in Fig. 2(a). When gate
voltage 2 is applied to gate electrode 2 and the twodimensional electron system directly below the gateelectrode is depleted, a junction (width less than 1μm) is formed at which the fractional and integer
regions contact each other. The width of the junction
narrows as the negative voltage of gate voltage 2
increases and the depletion region widens.
In the experiment, a current was applied to the junction from the fractional QH side, and the transmitted
current flowing out of the junction to the integer QH
side was measured. We observed that the transmitted
current exceeds the input current at certain values ofgate voltage 2, which corresponds to changing thejunction width (Fig. 3(a)). When we measured thereflected current returning from the junction to thefractional QH side, the current of the opposite sign
to that of the input current was observed (Fig. 3(b)).
The increase in transmitted current and a negativereflected current indicate that Andreev reflection ofquasiparticles occurred. This result indicates that
Andreev reflection is not a phenomenon unique tosuperconductors but a universal phenomenon, demonstrating an important achievement in condensedmatter physics.

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—What kind of research will you be focusing on in the
future?
Topological insulators and the fractional QH effectboth exhibit interesting physical properties due to thenature of the sample (material) interior; however, it isat the edges and surfaces of the sample (i.e., at theinterface with the vacuum or with ordinary material)that they appear as phenomena observed in experiments. Therefore, to observe theoretically predicted,
interesting phenomena experimentally, it is importantto create not only pure crystals but also high-quality
interfaces. I haven’t much time to talk about it in thisinterview, according to theory, the interface between
a topological insulator and superconductor is also aplatform where new physical properties appear.
Although researchers worldwide are working to verify the predictions of the theory, a unified understanding has not yet been reached because either the results
are not as the theory predicts or they are as the theory
predicts but do not exclude the possibility of otherinterpretations. We are currently focusing on creating
various interfaces, including superconducting junctions, by using methods that nobody has attempted
before. The young researchers in our group are actually conducting the research, and I support them. I
hope that our research will result in an ideal interface
and bridge the gap between theory and experiment.
This research is unprecedented, so it is a continuous
process of trial and error, but it is both rewarding andfun.
4Front-line Researchers

Basic research is like creating a map of science.
By taking on the right challenges, I want to makea positive impact on the research community andsociety as a whole—What do you keep in mind as a researcher?
As I mentioned in the previous interview, I thinkthat the basic research I’m involved in is like creating
a map of science. In the field of physics, theory alone
does not determine whether a proposition is correct.
At this phase, a rough outline of the map is created.
To update the map to be more accurate, experiments
must be conducted to clarify and verify the theory.
While certain Nobel Prize-winning studies significantly rewrote the map, it is also important to accumulate small updates to the map. I want to contributeto the creation of maps through my research on controlling the interface between materials and explore
new properties of electrons. The social significanceof that research, i.e., the new properties of electrons
may be used for fault-tolerant quantum computing,motivates me.
I used to think of research as a means of self-realization, so whether it was my own idea, whether I
carried it out, and how I was evaluated by others as a
researcher were all important indicators for me. However, as I get older, I find myself becoming more
appreciative of the importance of all the people andthings that surround me. This appreciation includes
not only “standing on the shoulders of giants” butalso extending to all ordinary people and things.
Regardless of whether it is my idea, and regardless of
how I am evaluated, I want to use my energy to dosomething that will have a positive impact on the
research community and society as a whole. In otherwords, I want to do things that I’m not sure that I can
do and things that seem difficult but are worth doing,rather than things that I think I can do faster than others. Even if I take on a challenge that no one else isdoing and the results are not what I expect, if I am
doing it for the right reasons, the knowledge I gain
will be useful to me and the world outside. I still want
to do research that will make people exclaim, “Thatwas a breakthrough!” but to achieve such breakthroughs, I want to continue to take on the right challenges.

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—What is your message to younger researchers?
Undoubtedly, young people are more likely toaccomplish great things in the future, so I want them
to believe in their own potential and strive forward. In
the past few years, there have been several major
breakthroughs in my field of research, and all havebeen achieved by young researchers. I have thought
about some of the things I was close to doing, butwhen I actually observe their breakthrough research,
I realize that it was not so much that I was close but
rather that I had not pursued my ideas far enough.
Even if you are progressing toward an achievement,
if you don’t have the last piece in place, you won’t
know if you are close to making an achievement, andif you stop there, the possibilities that may haveexisted will be closed off. It is important to keep youreyes open and your ears to the ground to be sensitive
to information from the outside; however, if you
really have something you are aiming for, rather thanconvincing yourself that you have already worked
hard for years or that you have done so much, you
should keep asking yourself whether you have reallydone everything you need to do and whether there isa better way to do it. This message is not only foryoung people but also for myself as a reminder.
References
[1]

[2]

M. Hashisaka, T. Jonckheere, T. Akiho, S. Sasaki, J. Rech, T. Martin,
and K. Muraki, “Andreev Reflection of Fractional Quantum Hall
Quasiparticles,” Nat. Commun., Vol. 12, 2794, 2021. https://doi.
org/10.1038/s41467-021-23160-6
M. Hashisaka, T. Ito, T. Akiho, S. Sasaki, N. Kumada, N. Shibata, andK. Muraki, “Coherent-Incoherent Crossover of Charge and Neutral
Mode Transport as Evidence for the Disorder-Dominated Fractional
Edge Phase,” Phys. Rev. X, Vol. 13, 031024, 2023. https://doi.
org/10.1103/PhysRevX.13.031024

Interviewee profile
Koji Muraki received a B.E., M.E., and Ph.D.
in applied physics from the University of Tokyoin 1989, 1991, and 1994. He joined NTT Basic
Research Laboratories in 1994. From 2001 to
2002, he was a visiting researcher at the Max
Planck Institute for Solid State Research,
Stuttgart, Germany. His research interests arefocused on many-body effects in low-dimensional semiconductor structures. He is a member of
the Physical Society of Japan and the Japan
Society of Applied Physics.

5

Rising Researchers

Software Digital Twins for Reducing
Software Waste and Achieving a
Sustainable IT Society
Shinobu Saito
Distinguished Researcher,
NTT Computer and Data Science
Laboratories
Abstract

The global information and technology services market for2022 was reported to be 1.3 trillion U.S. dollars (about 150 trillionyen), and it’s been pointed out that the massive amount of software produced by this market demand, while bringing great value
to our daily lives, has also led to a variety of problems. There are
expectations that an approach that not only seeks to increase theamount of software (production) but to also reduce that amount(reduction) could help solve those problems. In this interview, we
asked NTT Distinguished Researcher Shinobu Saito about his research on “Software Digital Twins.”
Keywords: software waste, Software Digital Twins, Software 3Rs

Achieving an ideal environment for users anddevelopers through Software 3Rs (Reduce,
Reuse, and Recycle)—Dr. Saito, what kind of technology is “Software
Digital Twins”?
“Software Digital Twins” that I am now researching is a technology that reproduces the internal conditions of software in a digital world on the computer todiscover and predict locations (programs) where
software should be revised or deleted. It’s been
pointed out that the increase in software that is not
used at all called “software waste” is a major problem
that has come to encircle software in recent years. As
it turns out, software, which was originally producedwith the aim of making the world a better place, is
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also giving rise to a variety of problems. These problems are called “big code” or “software bloat.” The
former means that software that has become too big
is difficult to maintain by a limited number of people(developers). In this regard, it is predicted that theamount of software will eventually exceed the range
in which programmers are capable of managing it. In
overseas surveys, more than half of all programmers
said “The amount of program code that one must deal
with has increased by more than 100 times comparedwith that 10 years earlier.” The latter, meanwhile,means that software that has become overly abundant(bloated) is consuming system resources such as central processing units and memory on a large scale.
This results in excessive power consumption andcarbon dioxide emissions, which has a negative
impact on the global environment.
6

Rising Researchers

Develop

OperateHuman
resources

Computingresources

Recycle & Reuse
ReduceFig. 1. Vision of Software 3Rs.

After joining NTT DATA Corporation, I myself
thought for many years “What can be done to make iteasier for developers to create good software forusers?” Several years ago, however, I came across
two articles in a business magazine titled “Software
not used by companies and ignored by users is waste”
and “One-third of an average company’s information
technology (IT) budget is consumed as software
waste,” both of which shocked me. Indeed, it has also
been reported that more than half of the functions ina developed system are rarely used. I therefore began
to feel “There is the possibility that my research in theend will actually have a negative impact on people
and the Earth,” and I began to think of an approachthat could break through this situation.
Then, one day while thinking about this, when I
was helping my child in elementary school withsummer-vacation homework, I noticed that the concept of the 3Rs in relation to environmental problems
was introduced in the textbook. The 3Rs refer toReduce, Reuse, and Recycle. Seeing this, I thought“Shouldn’t this concept also be applicable to IT society that is constantly producing software?” I considered that, from here on, “developing” software thatcan enrich everyone’s life is necessary, but it is also
important for people and the environment to “eliminate” software that has been overly developed andbecome excessive. The concept born out of thesethoughts is “Software 3Rs” (Fig. 1), which promotes
not only the development of software but also the
reduction of unnecessary software and the reusing ofexisting software. In this way, I believe that we canachieve a sustainable IT society for both users and
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developers of software. Last year, I presented thisconcept at an international conference on software
engineering and received comments like “very interesting” from participating researchers.
—In particular, what kind of approach are you
researching?
I am currently researching Software Digital Twins
as an approach to implementing the Software 3Rs
concept. This idea came to me from research on digital twins that reproduce data collected from realworld objects such as cities and human bodies in adigital world on the computer. For example, since itis difficult to directly observe an actually functioning
brain or heart, research is progressing on using thedigital twin of a human body to express such organs
in digital space with the aim of investigating thecauses of disease, predicting the occurrences of disease, and even preventing disease. Software, as well,consists of an aggregation of programs, and directly
observing the internal conditions of working software
is said to be a difficult objective. As a result, correctly grasping “where the frequently used programsare” and conversely “where unused programs are”
can be extremely difficult. Consequently, my aim
with Software Digital Twins is to discover and predict
locations (programs) that are unnecessary and nonurgent or in need of improvement by reproducing
with high accuracy the internal conditions of “blackbox” software and making that content “fully visible”(Fig. 2).
This research is closely related to Digital Twin
7

Rising Researchers

Input

OutputSource code

SoftwareExecution log
Display internal software
conditions on the computer in theform of a city and underground.

Support the discovery of unnecessaryand non-urgent locations and points
for improvement within software.

Fig. 2. Overview of Software Digital Twins.

Computing (DTC), a major pillar of the Innovative
Optical and Wireless Network (IOWN) concept proposed by NTT. At present, studies of DTC are proceeding in areas targeting the real world such asurban management and medical treatment. In contrast to this approach that attempts to reproduce thereal world in the cyber world, my research attempts
to reproduce a cyber world in another cyber world,that is, to reproduce the interior of software runningon a computer on another computer. Here, reproducing a cyber entity as another cyber entity may appear
at first glance to be somewhat strange, but I believethat this approach can enable humans such as software architects to accurately understand the internal
execution conditions of software for the first time andfacilitate predictions and simulations.
Main data used for accurately reproducing theexecution conditions of software are of two types:“source code” and “execution log” that records program operation. In the latter, the collection of theexecution log presents a major hurdle to making
advances in research and achieving practical implementation. The ideal method would be to record theoperation of “all locations (programs)” inside software during “all periods” in which the software is
executed. This, however, would require that software
engineers create a new program to record that operation at all locations. In addition, attempting to collect
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the execution log in all periods of execution would
consume an excessive amount of computing resources, which in itself would have a negative impact on
people and the environment, thereby defeating ouroriginal purpose.
Given the above, the technique that I am studying
in my current research will estimate and predict execution conditions throughout the software from execution log data obtained in limited periods at limited
locations within the software. My aim here is toestablish a technique that applies fields such as statistical analysis and machine learning through joint
research with universities.
Continue with “solitary” and “interaction”
activities to ensure that research does not end
with basic research—Please tell us about your research vision going
forward.
One research achievement in Software Digital
Twins to come out so far is ProcessCity, which istechnology for visualizing the usage frequency ofeach function in a business system and the operationof the entire system in a three-dimensional manner.
We have already provided this technology to several
NTT operating companies, and at NTT R&D Forum8

Rising Researchers

Requirementsdefinition process

Dismantlingprocess

Development
process

1. Software that will satisfy
users must be considered.

2. Developer must quickly andaccurately develop software.

Technology for designing
software based onuser requirements

Technology for developing
highly efficient andhigh-quality software

3. Software must be removed
and cleaned up.

Technology for dismantling
unnecessary andnon-urgent software

Technology that produces software
cannot by itself solve problems.

Fig. 3. Dismantling process in software development.

2022, we held a joint exhibit and a press release wasissued with one of those companies. I also publisheda paper with members of another operating company
to which this technology had been provided, and wewere honored to receive a best paper award at thelargest software-engineering international conference in the Asia-Pacific region held in 2022.
At present, it is said that the cost of maintaining
aging and complex old systems called “legacy systems” has risen to 60–70% of a company’s IT budget.
In addition, there have been cases in which surveys
conducted for discovering system functions that
could be scaled down or discontinued took months tocomplete. Consequently, the first thing that could beachieved by using the results of this research is a
shortening of the survey period and improvement in
the accuracy of the survey itself thereby reducing thelabor required in the survey step by 20–30% andeventually to as much as 10% of the current amount.
It was reported that the global IT services market
for 2022 was 1.3 trillion U.S. dollars (about 150 trillion yen), and according to the business magazinethat I mentioned earlier, it’s been calculated thatabout one-third of those IT services, or 50 trillion
yen, is being wasted. Of course, it would be difficult
for NTT by itself to reduce such software waste
throughout the world, but I would nevertheless like tocreate technology that could help reduce such a huge
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amount of waste on the scale of the national budget
and to connect this effort to providing great value toNTT’s corporate customers.
Additionally, on looking at the IT services industry
going forward, I anticipate that an industry for the
demolition of software in a safe and secure manner
will probably come to be formed. In this sense, if
producing software is a “construction industry,” thenremoving (deleting) software is a “demolition industry.” By making further progress in my research, myultimate goal is to form a new industry and create
new business opportunities and to make the software
dismantling business one of NTT’s core businessareas (Fig. 3).
—What is your impression of NTT laboratories?
As the name implies, NTT Computer and Data Science Laboratories that I belong to conducts research
related to computers and data, and in this capacity, it
is involved in a wide variety of research across all
sorts of businesses and industries. NTT Group companies include both companies that develop softwareand companies that use software, which is why I
believe that NTT laboratories are especially strong inboth user and development fields. The scope of stakeholders is broad, and I am given opportunities forexchanging opinions with group companies from the9

Rising Researchers

standpoint of using software, so I think I am blessed
to be in such an environment that helps me make real
progress in my research.
Moreover, on meeting with people from companies
outside the NTT Group, there are many occasions inwhich I can feel the name value of NTT. For example,
when attending an international conference for the
first time 10 years ago, I knew nobody there, but on
walking by myself to the venue after receiving myname tag at the reception desk, someone walking
next to me noticed my name tag and said in a very
friendly manner: “Ah, NTT! Do you know Mr. XX?”This person is a very famous professor in the software
engineering community, and thanks to this chance
happening, I still talk with him and discuss research
whenever we meet up at an international conference.
Of course, the name value of NTT does not guaranteethat research will always go well, but it certainly
gives me a reassuring feeling whenever I go to an
unfamiliar environment or place.
—Dr. Saito, please leave us with a message forresearchers, students, and business partners.
As I conduct my research at NTT, I have made thewords “there is no research that ends with basic
research” into a guiding principle. I first learned
about this concept on joining NTT DATA fromresearchers that had come to my department fromNTT laboratories. What this meant was that “Evenbasic research that seems unlikely to have an immediate application must be meaningful in the sense ofbeing useful in some way. If it has no meaning (if nomeaning can be discussed), it is not basic research,

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and in fact, it is not research in the first place.” I keepthese words in mind all the time, and since research isfunded, I make an effort to present “the meaning ofresearch” in terms of how those research results will
someday be useful.
At around the same time, I remember well thewords of a senior colleague, who said, “Research, inthe end, is a solitary endeavor.” Research requires
originality, so in some respects, I think “solitary” iscorrect here. Looking back at my own research when
I was at the stage of thinking about a certain basic
concept, there were many times when I could notverbalize it well and just kept worrying about it bymyself. However, at the stage of actually implementingthat concept, I found that it was necessary to gain thecooperation of many people. NTT provides an environment and the opportunities to interact with otherpeople and other companies, so there are many uplifting (exciting) times that occur when acquiring new
knowledge from outside one’s field and seeing a newworld that one could not reach by oneself. Goingforward, I plan to pursue my research with great feeling and conviction and to make up for what I am
lacking by interacting with many of my fellow
researchers with the hope that we can conduct
research together.
Interviewee profile
Shinobu Saito received his M.S. degree from
Keio University in 2001 and joined NTT DATA
Corporation in the same year. He received his
Ph.D. degree (engineering) from Keio University
in 2007. He is engaged in the research of new
software engineering for the digital era. He is arecipient of the 2022 IPSJ-CS Outstanding
Achievement and Contribution Award and the
APSEC2022 Best SEIP (Software Engineering inPractice) Paper Award among other awards. He
was a visiting researcher at the Institute forSoftware Research (ISR), University of California
at Irvine, from 2016 to 2018 and was a distinguished researcher at NTT Software Innovation
Center from 2018 to 2021. He has been affiliatedwith NTT Computer and Data Science
Laboratories since 2021.

10

Feature Articles: Recent Developments in the IOWN
Global Forum

Latest Activities in the IOWN Global
Forum
Yoshitake Tajima and Yosuke Aragane
Abstract

With a view to creating a smart world, the concept of the Innovative Optical and Wireless Network(IOWN) aims to create a next-generation communication and computing infrastructure that features
ultra-high capacity, ultra-low latency, and ultra-low power consumption. With input from global member
companies, the IOWN Global Forum has been developing technical architectures and use cases andconducting proof of concept (PoC) activities and implementation verification. This article introduces thelatest activities of the IOWN Global Forum, as well as the PoC Reference documents and referenceimplementation-model documents that reflect the results of these efforts.
Keywords: IOWN, Global Forum, optical network

1. IOWN concept and the IOWN Global ForumIn May 2019, with a view to creating a sustainable
and prosperous smart world, NTT proposed the concept of the Innovative Optical and Wireless Network(IOWN), which will break through current limitations and build a communication and computing
infrastructure that features ultra-high capacity, ultralow latency, and ultra-low power consumption. NTT
is conducting research and development with thegoals of increasing power efficiency by a factor of100, transmission capacity by a factor of 125, andend-to-end low latency performance by a factor of
200 by the year 2030. Achieving these goals will callfor a major transformation in information processing,communication, and network infrastructure, which inturn will require the development and combination ofmany innovative technologies. Such endeavors cannot be achieved by the NTT Group alone. Thus, inJanuary 2020, Intel Corporation, Sony Corporation,
and NTT Corporation established the IOWN Global
Forum, an international non-profit organization dedicated to the future of communications. During thefour years since then, the forum has been developing
the innovative technical frameworks, technical specifications, and reference architectures needed toachieve the above goals and pressed forward to actuNTT Technical Review

Vol. 22 No. 2 Feb. 2024

alize a new communication and computing infrastructure, IOWN. Figure 1 shows the overall technical structure of IOWN [1]. What is immediately
apparent is that its network, the Open All-Photonic
Network (Open APN), enables communication withdeterministic transmission rates and latency. Placed
on top of that is an architecture called a data-centric
infrastructure (DCI), which achieves efficient datatransfer and processing using accelerators. Via the
APN, two remotely located DCIs can transfer data athigh speed and with low latency and combine multiple distributed datacenters to form one large virtual
datacenter. The IOWN Global Forum is developing
the IOWN Data Hub (IDH) to enable scalable andhighly available database storage that is based on the
distributed database architecture within a cluster byusing the above capabilities of the DCI. The forum
will implement various use cases on top of the IDH
and enable Digital Twin Computing by linking digital
twins that digitally represent various objects in thereal world. It will feed the results of Digital Twin
Computing back to the real world to create a smart
world.
The activities of the IOWN Global Forum are characterized by the fact that it studies not only technology but also use cases so that the desired smart world
can be envisioned in concrete terms from the11

Feature Articles

Interactive Live
Music

Area
Management

Industry
Management

Digital Twin Framework
Wireless connectivity meetingextreme QoS requirements
and high energy efficiency

Efficient and rights-aware
data store/exchange
serviceWide-area sensing
servicePost-quantum security
for data at rest, in motion,and in process

IOWN for
Mobile Networks

Data Hub

Fiber Sensing

IOWNsec

IOWN Computing: Moving and processing data
while meeting extreme QoS requirements and high energy efficiency
Data-centric infrastructure (DCI)IOWN Networking: Connecting endpoints while achieving deterministic QoS and high energy efficiency
Open All-Photonic Network (APN)

Fig. 1. Structure of IOWN technologies.

Board

Vision Steering
Committee

Technology Steering
Committee

Vision Steering
Committee

Technology Working
Group

Use Case
Working Group

Liaison Working Group

Open APN Architecture
Task Force

In-Vehicle Communication
Task Force

Open APN Wavelength
Availability Task ForceIOWN Digital Twin
Framework Task Force

Open APN Fiber Sensing
Task Force

Use Case Document Task
Force

IOWN for Mobile Networks
Task Force
Data-Centric Infrastructure
Task Force

RIM Task Force

PoC Consultation Task
Force

IOWN Data Hub Task
Force
IOWN Security Task Force

Fig. 2. Organization chart of IOWN Global Forum.

beginning. Two working groups (WGs) have been
established for this purpose: the Use Case WG andTechnology WG (Fig. 2). The Use Case WG develops the details of applications in line with the visionof a smart world, estimates IOWN’s potential impact
NTT Technical Review

Vol. 22 No. 2 Feb. 2024

on business, and discusses technical requirements,
while the Technology WG discusses technical solutions, such as reference architectures, protocols,interfaces, and other specifications. The two WGs
work in close collaboration with each other (Fig. 3).
12

Feature Articles

Createspecific use cases

Establish technicalroadmap

Popularization and deployment(cooperation withstandardization organizations)

Develop technical specifications(i.e., architecture, requirements)

Use cases and applications

Technical solutions(IOWN Global Forum vision, motivating use cases, potential
business-impact estimations, technology requirements)(reference architecture, protocols, interfaces, specifications)SmartenergySmartcitiesSmartmobility

Smartfinance

Networking
optical &wireless

Smartentertainment

Distributed
computingMore use cases and applications

Photonics &optoelectronics

Devices,
interfaces& terminals

More technologies

Fig. 3. Forum activities.

Phase 12022/1

Vision 2030

Use case
Two UC categories: AIC, CPS

Technology
IOWN GF fundamental techframework with APN and DCI• Pre-Commercialization trials• Specification Updates• Roadmap for Commercialization
Liaison Program to Establish
External Collaboration

PoC

PoC
Use case

Technology

AIC/CPS Use Case Specific RIM
Digital Twin Framework

Arch and component technology study• APN- Arch, UWOT• DCI- Arch. DPA• Mobile Network with APN & DCI• Data Hub with APN & DCI• Fiber Sensing with APN & DCI• RIM: CPS-AM security

2020/12

Select additional PoC cases

Technology

Technology
Technology development for UCTR1.0 use cases
APN and DCI arch enhancement, new component Tech, e.g.,• Requirements on co-packaging• Coverage extension
PoC TRUC TR Updates
Architecture TR Updates
Vision 2030 Updates
Interim DocsTS

2022/1
CPS: cyber physical systems
DCI: data-centric infrastructure
DPA: data plane acceleration

AIC and CPS use cases for mid-term and long-term applications, e.g.,• Interactive free-view point communications– transmission of full
spatial information

Use case

UC Interim Doc
Sys & Tech Outlook
UC TR
Architecture TR

2024/12Preparation of Real World
Deployment and Business Impact

Select PoC cases
Minimal viable PoC TR

Vision 2023 WP

AIC: Al (artificial intelligence)
integrated communications
AM: area management
APN: All-Photonics Network

Phase 32023/7

AIC - Entertainment. Remote operation,
Navigation, Human Augmentation
CPS- Area, Mobility, Industry, Net Infra,
Healthcare, Smart Grid, Society Mgmt

Use case

VisionPhase 2

Acceleration toward Vision 2030/
Use Case Realization• Technical Specification Work• Reference Implementation Model Expansion & Acceleration• PoC Activities• Vision-2030 Update• Use Case Update• Architecture Update

Direction and Plan Definitions• Vision-2030• Use Cases-AIC, CPS• Architecture-APN, DCI, IDH, FS, IMN, RIM

FS: fiber sensing
IDH: IOWN Data Hub
IMN: IOWN Mobile Network

Technology development for UCTR2.0 use cases
APN and DCI arch enhancement
New component tech*e.g., TBD
IOWN domain-specific systems*e.g., TBD
PoC TRNew UC TR
New Tech TRTS2024/122023/7
PoC: proof of concept
RIM: reference implementation model
TR: technical report

TS: technical specification
https://iowngf.org/roadmap/
UCTR: use case technical report
UWOT: ultra wideband optical transmission
WP: white paper

Fig. 4. IOWN Global Forum Vision 2030 Roadmap.

The IOWN Global Forum has developed and followed a roadmap consisting of phases, each of whichspanning about eighteen months. In Phase 1 (up to
January 2022), entitled “Direction and Plan Definition,” the forum formulated a vision, developed
major use cases, established a basic technical framework, and identified the issues that need to be considered. In Phase 2 (up to July 2023), entitled “Acceleration toward Vision 2030/Use Case Realization,”
the forum updated the vision, use cases, and architecture and developed technical specifications and reference implementation models (RIMs), and conducted
proof of concept (PoC) activities. Currently, in Phase
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3, entitled “Preparation of Real-World Deployment
and Business Impact,” the IOWN Global Forum isaccelerating its efforts toward the actualization of
IOWN (Fig. 4).
As a way of presenting the main initiatives of the
IOWN Global Forum, this article introduces theresults of Phase 2, the forum’s organization, the statusof its activities, and its planned activities for the
future.

13

Feature Articles

Use Case PoC

Technology Release-1

CPS-AM RIM PoC Reference

Technical PoC
IOWN Data
Hub PoC
Reference

6 Technicaldocuments

Data-Centric
Infrastructure
Functional
Architecture

Mobile Fronthaulover APN PoC
Reference

RDMA over
Open APN
PoC
Reference

Open APN
Fiber Sensing
PoC
Reference
Open APN
Architecture PoC
Reference

Fig. 5. Seven released PoC Reference documents.

2. Phase 2 activities and key results
2.1 PoC References
In Phase 1, the IOWN Global Forum studied thearchitectures of the Open APN, DCI, IDH, and othertechnical elements of IOWN, and released six technical documents in January 2022.
The main activities in Phase 2 were to study implementation details and conduct PoC activities on thebasis of the architectures developed in Phase 1. To
advance PoC activities and promote market deployment and collaboration among the parties concerned
beyond simple technical demonstration, the IOWN
Global Forum compiled PoC Reference documents,
which summarize reference use cases, the featuresthat key technologies must deliver, and evaluation
metrics for each technical theme. By November
2022, the forum had released the following sevendocuments (Fig. 5):(1)	Open APN Architecture PoC Reference(2) RDMA over Open APN PoC Reference(3)	Data-centric-infrastructure-as-a-service PoC
Reference(4) Mobile Fronthaul over APN PoC Reference(5) IOWN Data Hub PoC Reference(6)	Fiber Sensing Crosstalk Study for Open APN
PoC Reference(7)	PoC Reference: Reference Implementation
Model for the Area Management Security Use
Case
The main PoC Reference documents that will be
discussed in the Feature Articles in this issue are
introduced below.
The Open APN Architecture is an open architecture
for building the multi-vendor APN that enables comNTT Technical Review

Vol. 22 No. 2 Feb. 2024

munications with deterministic transmission rates
and latency. PoC Reference (1) describes dynamic
optical path design, open interfaces, and support for
multi-vendor environments. PoC Reference (4)describes applying the Open APN to mobile fronthaul
and presents interface requirements, dynamic pathswitching, etc. to enable mobile network operators to
use the Open APN.
The IDH is an architecture for database storage thatis hierarchically distributed to meet stringent requirements. PoC Reference (5) presents smart factory,
smart grid, and metaverse scenarios in which the IDH
is applied and describes the configuration and evaluation of the implementation.
A DCI is an architecture for streamlining data transfer by incorporating network interfaces into dataprocessing modules, such as accelerators. This
enables multiple remotely located DCIs to share
information technology (IT) resources by transferring data at high speed and with low latency via the
APN. PoC Reference (3) shows use cases, such asarea management, virtualized radio access networks,
and disaggregated IDH, and describes the implementation and evaluation of the PoC.
2.2 RIMsThe IOWN Global Forum has developed RIMs forpromising use cases. It is important to develop fullstack engineering of these models by taking the characteristics of each use case into consideration. RIMs
provide best practices for overall implementation.
The following RIM documents have been released:(1)	RIM for the Interactive Live Music Entertainment Use Case(2)	RIM for the Area Management Security Use
14

Feature Articles

More than 130 members
from Asia, Americas, and Europe(as of September 2023)

130

Sponsor
GeneralAcademic
research

88

39
3
20

J

21

an

J

22

20

20

20

an

J

an

23

20

ep

S

Fig. 6. Increase in IOWN Global Forum members.

Case(3)	RIM for the Remote-Controlled Robotic
Inspection Use Case
Interactive Live Music Entertainment is a use caseselected as an AI-Integrated Communication. Thisuse case delivers the musical performances of artists
with volumetric video and audio to the audience inreal time and reflects the audience’s reactions in thevirtual space. RIM document (1) provides the technical specifications of the devices used in the use caseand functional requirements of the system and presents guidelines for the implementation of the overall
configuration.
Area Management Security is a use case selected asa cyber-physical system. In this use case, a large
number of surveillance cameras are installed in urban
areas and facilities to prevent crime and ensure security. The Open APN, DCI, and IDH are applied to thisuse case. RIM document (2) shows an analysis of thedata flows and workload of camera-captured videos
and other data in an implementation configurationand describes the configuration and effects of eachtechnology when it is applied.
Remote-Controlled Robotic Inspection is a use casefor the remote control of a factory, as used by petrochemical plants in their production processes. RIM
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Vol. 22 No. 2 Feb. 2024

document (3) presents the requirements to be met by
the data to be acquired, remote-control requirements,
an analysis of data flows, and the implementation
configuration and its effects.
As described above, the IOWN Global Forum has
been analyzing the requirements, studying the effectsof the PoC-implementation models for specific use
cases on the basis of the PoC Reference documents
for each IOWN component technology, releasing theresults of these studies, and conducting actual PoC
verification projects on the basis of these results. The
reports on the results of these PoC verification projects will be released in the coming years.
3. Organization and activities of the IOWN
Global Forum
3.1 Expansion of membership
The IOWN Global Forum was established in January 2020 by three companies (Intel, Sony, and NTT).
The number of members has since been rapidly
increasing, reaching 39 organizations by January
2021, 88 by January 2022, and exceeding 130 bySeptember 2023. New members are joining almost
every month (Fig. 6).
Reflecting the characteristics of the forum’s activities
15

Feature Articles

Fig. 7. IOWN Global Forum Member Meeting in Munich.

wherein use-case studies and technical studies proceed hand in hand, not only those who study anddevelop IOWN Global Forum technologies but also
many of those who use these technologies participate
in the forum. Participation in the IOWN Global
Forum is not confined to enterprises. Research institutes, universities, and academic institutions are also
actively involved. Municipalities are also taking part,and major cities around the world have expressed
their interest [2].
3.2 Recent activities of the IOWN Global Forum
Since its inception, due to the COVID-19 pandemic, the IOWN Global Forum has conducted its activities online. However, as the pandemic has now subsided globally and there has been a revival of social
activities from the latter half of 2022, the forum has
gradually shifted to holding a hybrid of online andoffline meetings. In October 2022, the 5th Member
Meeting—the first locally held member meeting—took place in New York City in a hybrid format, with
136 local participants and more than 300 online parNTT Technical Review

Vol. 22 No. 2 Feb. 2024

ticipants from 44 member organizations located invarious countries.
In April 2023, after the peak of the 8th coronavirus
wave in Japan, the 3rd Annual Member Meeting—thefirst locally held annual member meeting—was held
in Osaka in a hybrid format. More than 400 participants from 78 member organizations from different
countries gathered in Osaka while many others participated online. There was lively discussion around
updating the forum’s vision and use cases, and therelated technologies were intensively considered.
In September 2023, the 6th Member Meeting washeld in Munich [3]. This was the first member meeting held in Europe and was attended by more than
400 people (190 locally) from 89 member organizations from various countries (Fig. 7). All meetings
were operated in a hybrid format, which allowed
many people to participate in meetings online while
enabling local participants to hold in-depth discussions. Prior to the meeting, a call for proposals
regarding activities in Phase 3 was issued, and 34
proposals were received. In the Munich meeting,16

Feature Articles

breakout workshops, each dedicated to a specificsubject category, were organized and active technicaldiscussions on these proposals took place. The meeting also officially released a reference document that
identified key values and presented a roadmap fortechnological evolution [4]. The values identified
included the importance of a holistic approach, animplementation-driven approach, and system-level
solutions. A roadmap for evolution in networking andcomputing was presented. “An Implementation of
Heterogeneous and Disaggregated Computing for
DCI as a Service” was also approved as the first recognized PoC report. More PoC reports will be published in the coming years to demonstrate the value
and performance of IOWN technologies.
3.3 Other activities
In parallel with the Use Case and Technology WGs,
the Liaison WG of the IOWN Global Forum has been
active, promoting collaboration with other technicaland standardization organizations [5]. The Liaison
WG exchanges various types of information with collaborating organizations, jointly studies specifications, and seeks to have the IOWN Global Forum’s
technologies adopted as standards. The Liaison WG
is currently collaborating with the International Telecommunication Union (ITU) Radiocommunication
Sector, the ITU Telecommunication Standardization
Sector, the Linux Foundation, OpenROADM, andother organizations, and plans to expand the scope ofcollaborating organizations.
The IOWN Global Forum is also actively engaged
in external activities as part of its marketing initiative. In addition to giving lectures and demonstrations at events held by member companies, the forum
participates in events hosted by the information andcommunication industry and academic conferences,giving speeches and organizing exhibitions.
In 2023, the IOWN Global Forum jointly set up an
exhibit with other companies at the Mobile WorldNTT Technical Review

Vol. 22 No. 2 Feb. 2024

Congress (MWC) held in Barcelona in February,gave a speech at the Optical Fiber Communication
Conference and Exposition (OFC) held in San Diego
in March and at the Institute of Electrical and Electronics Engineers (IEEE) International Conference
on Communications held in Rome in June. At the
NTT booth at Interop Tokyo 2023 held in Chiba,
Japan in June, NTT exhibited the remote control of arobot and a virtual-reality table-tennis application
using remote graphics processing units to demonstrate the ultra-low latency achieved using the OpenAPN.
4. Activities and prospects for Phase 3
In Phase 3, entitled “Preparation of Real-World
Deployment and Business Impact,” the IOWN Global Forum aims to further develop technology, expand
the organization and activities, and create businesscases toward the deployment of IOWN. The forum
will also conduct PoC and technical evaluation of
specific use cases and release PoC-result reports. It
will develop technical-specification documents,
deepen collaboration with other organizations, andwork toward standardization of the forum’s specifications. It will also seek to deploy IOWN by expanding
support for the forum members, such as holding local
events and seminars, to accelerate studies tailored toeach country or region so that many user companies
can use IOWN in their respective businesses.
References
[1]
[2]
[3]
[4]
[5]

IOWN Global Forum technology documents, https://iowngf.org/
technology/
IOWN Global Forum members, https://iowngf.org/members/
IOWN Global Forum 6th Member Meeting September 2023 – Highlights, https://iowngf.org/event/iown-global-forum-6th-membermeeting/
IOWN Global Forum, “IOWN Global Forum: Key Values and Technology Evolution Roadmap,” https://iowngf.org/wp-content/uploads/
formidable/21/IOWN-GF-RD-KVaTE_Roadmap-1.0-1.pdf
IOWN Global Forum’s Liaison Program, https://iowngf.org/liaisons/17Feature Articles

Yoshitake Tajima

Director, IOWN Development Office,Research and Development Planning Department, Research and Development Market Strategy Division, NTT Corporation.
He received a B.E in electronic engineeringand M.E. in information and communicationengineering from the University of Tokyo in
1997 and 1999. He joined NTT Information
Sharing Platform Laboratories in 1999. He has
been mainly engaged in the research and development (R&D) of network security and computing architecture. He also received an MSIA from
School of Business, Purdue University, USA in
2014. He is currently engaged in the promotion
of IOWN R&D at NTT and administrative operation of the IOWN Global Forum. He is a memberof IEEE, the Institute of Electronics, Information
and Communication Engineers (IEICE), andInformation Processing Society of Japan (IPSJ).

NTT Technical Review

Vol. 22 No. 2 Feb. 2024

Yosuke Aragane

Vice President, Head of IOWN Development
Office, Research and Development Planning
Department, Research and Development Market
Strategy Division, NTT Corporation.
He received an M.S. and Ph.D. in engineeringfrom the Tokyo Institute of Technology in 1997
and 2005. Since joining NTT in 1997, his major
research area was cyber security, especially in
CSIRT (computer security incident responseteam) operations. Since 2016, he has been thehead of Cyber Security R&D Promotion in NTT
Research and Development Planning Dept. In
2019, he became a vice president of IOWN
Development Office. He is an alternate director,
leader of Recruitment Taskforce, and co-leaderof Officer team in the IOWN Global Forum. His
current responsibilities are managing IOWN
R&D in NTT labs and leading the IOWN Global
Forum with diverse partners. He has the CISSP
certification and is a member of IEEE, IEICE,
and IPSJ.

18

Feature Articles: Recent Developments in the IOWN
Global Forum

Activities for Detailing theArchitecture of the Open APN andPromoting Its Practical Application
Yoshihiko Kainuma, Tomonori Takeda, Jun-ichi Kani,and Hideki Nishizawa
Abstract

The IOWN Global Forum has proposed the Open All-Photonic Network (Open APN) as a network
infrastructure that achieves low latency and low power consumption and issued an architecture document entitled “Open All-Photonic Network Functional Architecture,” in early 2022. This article introduces the activities carried out since the release of the above architecture document to detail the OpenAPN architecture and promote its practical application.
Keywords: IOWN, Open APN, PoC

1. Introduction
The Open All-Photonic Network (Open APN) is an
open architecture for photonics networking proposedby the IOWN Global Forum (IOWN GF), which is
studying ways that would enable service providers tointegrate photonics networking capabilities with theiroverall computing and networking infrastructure at afiner level of granularity. Since the architecture document, Open All-Photonic Network Functional Architecture release 1 [1], was issued in early 2022, theforum conducted a proof of concept (PoC) based on
this architecture document and issued the Open AllPhotonic Network Functional Architecture release 2
in October 2023 [2], which expands and details thearchitecture. This article introduces the forum’s
activities since the publication of the architecture
document release 1.
2. Open APN
Let us first briefly explain what the Open APN is. It
is a network that enables different locations to be
directly connected using optical wavelength paths
and consists of Open APN Transceivers (APN-Ts),
NTT Technical Review

Vol. 22 No. 2 Feb. 2024

Open APN Gateways (APN-Gs), and Open APN
Interchanges (APN-Is). An APN-T is an endpoint foran optical wavelength path and transmits and receives
optical signals. An APN-G is a gateway for an optical
wavelength path and sets up control channels to communicate with the connected APN-Ts, executes user
plane admission control, multiplexes/demultiplexes,
turns back, and adds/drops optical wavelength paths.
An APN-I is an interchange for an optical wavelength
path, executes wavelength cross-connect, and provides adaptation between interfaces (Fig. 1).
For more details on the architecture, please refer tothe article, “Study on Open All-Photonic Network in
IOWN Global Forum” in the May 2022 issue of thisjournal [3].
3. Open APN PoCIOWN GF planned the Open APN PoC [4] activities to show the global market that the Open APNFunctional Architecture is not a technology of the
future but can be built and operated using technologies already available. These activities have prompted many organizations around the world to aim atbuilding and introducing the Open APN, create use
19

Feature Articles

Fig. 1. Open APN reference architecture for optical wavelength path services.

cases, and deploy them in the global market. IOWNGF has published a PoC Reference document, which
provides guidelines for conducting PoC, enablinganyone to undertake PoC under a common set of
guidelines. The PoC Reference document for theOpen APN provides guidelines for the following
items to enable those interested to conduct a comprehensive demonstration of the architecture defined not
only by the two task forces (TFs) studying the OpenAPN architecture, namely the Open APN Architecture TF and Open APN Wavelength Availability TF,
but also by the Open APN Fiber Sensing TF, which is
studying technology for sensing using optical fibers.
The functions subject to evaluation as defined in the
PoC Reference document are introduced below.
3.1 Basic functions of an APN-G(1) Setting up a control channel for an APN-T(2)	Executing user plane admission control of optical signals(3)	Multiplexing/demultiplexing optical wavelength paths(4) Turning back optical wavelength paths(5) Adding/dropping optical wavelength paths(a)	Flexible Bridging Service: A service that aggregates multiple data flows with extremely strinNTT Technical Review

Vol. 22 No. 2 Feb. 2024

gent quality-of-service requirements and forwards them into a single optical wavelength
path(b)	Open interface: An open interface used to connect devices from different vendors to the OpenAPN Controller (APN-C) or used for control by
the APN-C(c)	Multi-vendor support: Interoperability between
an APN-T and APN-G supplied by different
vendors(d)	Automatic provisioning: Automatic provisioning of optical wavelength paths, including
physical design, on the basis of link parameterssuch as fiber type and power profile(e)	Mechanism for transceiver connection at usersites: Automatic registration of transceivers atuser sites that terminate optical wavelength
paths(f)	Monitoring: Automatic and periodic collectionof monitoring data from an APN-T and APN-G
by the APN-C(g)	Fiber sensing: Confirmation of fiber sensing at
an APN-G under the following conditions:•	The interrogator is an optical time-domainreflectometer for general loss measurements.
It uses a wavelength of 1550 nm.
20

Feature Articles•	The circulators and couplers are general commercial products.
•	The optical switch is a commercial switchthat supports 1550 nm.
•	The sensing fiber is a commercial single-mode
optical fiber with a length of more than 10 km.
Many IOWN GF member companies have conducted PoC on the basis of this PoC Reference document. IOWN GF will publish the results of PoC
implementation with a view to promoting further
study and expanding the number of participants.
4. Updating of architecture document
IOWN GF issued the Open APN Functional Architecture release 2 document in October 2023 [2]. This
document is an update of the release 1 architecture
document issued in early 2022 [1]. Its main focus isexpanding and detailing the basic architecture, control plane architecture, and user plane architecture.
4.1 Basic architecture
The basic architecture of the Open APN has
evolved into a two-layer structure with the definitionof a new fiber layer in addition to the wavelengthlayer defined in the release 1 document. The wavelength-layer architecture is called Open APN Wavelength Exchange (Open APN.WX) while the fiber
layer architecture is called Open APN Fiber Exchange(Open APN.FX). Open APN.FX newly defines OpenAPN Fiber Cross-connect (APN-FX), which is a
gateway for setting up a fiber path using a physicalfiber to connect endpoints in the Open APN, andvarious interfaces on the fiber path. It also clearly
describes how these layers are combined to set up
fiber paths and wavelength paths (Fig. 2).
While the architecture in the release 1 document
had a point-to-point (PtP) configuration, the release 2
architecture additionally incorporates a point-tomultipoint (PtMP) configuration, in which a single
signal is branched into multiple points. This new
document describes both PtMP in Open APN.WX
and PtMP in Open APN.FX.
4.2 Control and management plane architecture
The new document further details control and management plane architecture for optical wavelength
paths in a PtP configuration. Assuming a reference
model in which an APN-T is deployed at the user’s
location, the document systematically presents thefunctions required for the APN-C to set up an end-toend optical wavelength path including user devices
NTT Technical Review

Vol. 22 No. 2 Feb. 2024

and describes the application programming interfaces(APIs) used for interfacing with the orchestrator andeach APN node. It also clarifies how the APN-C
cooperates with each entity to control and manage
optical wavelength paths (Fig. 3).
The use of existing open interfaces, such as OpenConfig, OpenROADM (reconfigurable optical adddrop multiplexer), and Telephony Application Program Interface (TAPI), in implementing the southbound interface is also described (Fig. 4).
4.3 User plane architecture
The release 1 document defined the concept ofGroup of Optically Interoperable Ports (GOIP),
which is a subnetwork within the Open APN that canconnect to other GOIP subnetworks through opticalpaths. The release 2 document newly describes theinterworking between GOIPs, which was treated as
an item for future study in the release 1 document.
The release 2 document defines a method for setting
up an optical connection when a wavelength can be
assigned and the required transmission characteristics are satisfied and a method for setting up a connection that involves electrical conversion using
optical-electrical-optical (O/E/O) repeaters or Ethernet/Optical Transport Network (OTN) connections.
These methods make it possible to construct the Open
APN that scales beyond GOIPs (Figs. 5(a), (b)).
In addition to these updates, annexes have been
added to the release 2 document. The annexes
describe methods for implementing each Open APN
node, use cases, and PtMP implementation examples,
thus providing more detailed guidelines for implementing and using the Open APN.
5. Activities at NTT
NTT’s contribution to these IOWN GF activities
has not been confined to the submission of documents but also includes other activities. Two of these
are introduced below.
5.1 D emonstration test of Open APN function
group
Prior to the publication of the release 2 document,
NTT laboratories conducted, within a laboratory, ademonstration test of “a group of functions thatenable high-capacity, low-latency communications
between required locations when needed,” which is amandatory condition for further expanding use casesin the Open APN architecture [5]. This functiongroup enables Open APN endpoints to be installed at
21

Feature Articles

Fig. 2. Basic architecture of the Open APN.

Fig. 3. Example reference of APN-C functional model.

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22

Feature Articles

Fig. 4. Recommendation set of southbound interfaces for the APN-C.

GOIP(Reference bit rate:
400G)

GOIP
(Reference bit rate:
400G)

GOIP
(Reference bit rate:
400G)(a) Method for setting up an end-to-end optical connection(b) Method for setting up a connection that involves electrical conversion

Fig. 5. Inter-GOIP connections.

different sites, including user sites. This functiongroup consists of the following three functions(Fig. 6):(1)	A function for automatic design and provisioning of optical wavelength paths that satisfy service conditions, implemented throughcoordination and collaboration between usersite terminals and telecommunications operaNTT Technical Review

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tors’ devices, and function for adjustment,such as selection of an optimal mode(2)	A function for setting and managing optical
wavelength endpoints at a user site terminal
and function for passing/stopping optical signals at telecommunications operators’ deviceson the basis of the authentication status of theterminal
23

Feature Articles(1) Flexible on-demand connection between
user sites with an optical wavelength path
Function for automatic
design/provisioning of paths thatsatisfy service conditions
Optimal mode selection and otheradjustment functions(2) Placement of optical wavelength
endpoints at user sites

Function for configuration management of optical
wavelength endpoints at user sites (remote control,
authentication/registration/ID management)

Factory

Hospital
Optical signal
pass/stop function

Hospital

Broadcast station

Entertainment facility

Datacenter
User site

OfficeDatacenter

Carrier’s network

User site(3) Adaptation function that enables different
types of optical fibers to be connected withthe same optical wavelength path
Fig. 6. Demonstration test of an Open APN function group for on-demand wavelength connections between user sites.

(3)	An adaptation function that enables different
types of optical fibers to be connected witheach other while keeping the optical wavelength path unchanged
Using the results of the OpenROADM MultiSource Agreement and Telecom Infra Project Open
Optical & Packet Transport, which are organizations
promoting flexible and highly interoperable open
optical transmission systems, NTT is conducting afield test in the Tokyo metropolitan area to demonstrate that the system can operate under a variety ofconditions, including fiber lengths and loss levels that
occur in real-world environments. On the basis of theresults of this field test, NTT submitted documents
for the compilation of the release 2 document.
5.2 U
 se of the Open APN in a real environment
through a dynamic exhibit at a trade show
At Interop Tokyo 2023 held in June 2023, a dynamic exhibit of the Open APN was staged [6]. This
dynamic exhibit featured the following three points:(1)	A network connecting multiple remote locaNTT Technical Review

Vol. 22 No. 2 Feb. 2024

tions was constructed.
(2)	Various services, such as GPU (graphics processing unit) as a service, public cloud access,and internet access, were provided.
(3)	Multi-vendor connections of APN-G/Is andconnections of multi-vendor APN-Ts were
presented.
Through this dynamic exhibit, we were able toshow that the Open APN is a low-latency, low-jitter
network that can be built using multi-vendor devices.
By providing services that involve connections tosites outside the exhibition site at a large trade show,such as Interop, we were able to show that the OpenAPN is a cost-optimal solution in such cases because
it does not require separate fibers for each service.
Previously, the Open APN had been mainly constructed in restricted environments for demonstration
purposes. The exhibit at the Interop was the first version of the Open APN that had been constructed as a
network able to provide a variety of services in a situation that corresponded closely to a practical implementation. A report on the exhibit was presented at24

Feature Articles

the IOWN GF September 2023 Member Meeting
held in Munich as the event demonstrated that a new
step forward had been taken in the transition of theOpen APN from the PoC stage to practical application.

ther development of technologies and social implementation.
References[1]

6. Future development
This article introduced the Open APN-related
activities undertaken after the publication of therelease 1 architecture document. The Open APN is
expected to be used for various use cases in combination with the data-centric infrastructure, which is also
introduced in another article in this issue. As a network infrastructure for IOWN Data Hub and IOWN
Mobile Network, which were also introduced inanother article in this issue, the Open APN plays asignificant role in meeting extremely stringent
requirements. Together with many IOWN GF partners, NTT will continue to engage in a series of discussions and demonstrations to contribute to the fur-

Yoshihiko Kainuma

Senior Manager, NTT IOWN Development
Office, Research and Development Planning
Department, Research and Development Market
Strategy Division, NTT Corporation.
He received an M.E. in information and computer science from Keio University, Tokyo, in
2007. He joined NTT WEST in 2007 and NTT in
2021. He has been engaged in the research anddevelopment management of a next-generation
communications infrastructure and joint workwith partners to commercialize the infrastructure.

Tomonori Takeda

Senior Research Engineer, Supervisor, Network Architecture Project, NTT Network Service Systems Laboratories.
He received an M.E. in electronics, information, and communication engineering fromWaseda University, Tokyo, in 2001. He joined
NTT the same year and has been engaged inresearch and development on the next-generationtransport network architecture and next-generation mobile network architecture.

NTT Technical Review

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[2]
[3]

[4]
[5]

[6]

IOWN GF, “Open All-Photonic Network Functional Architecture,”
Ver. 1.0, Jan. 2022. https://iowngf.org/wp-content/uploads/formidable/
21/IOWN-GF-RD-Open-APN-Functional-Architecture-1.0-1.pdf
IOWN GF, “Open All-Photonic Network Functional Architecture,”
Ver. 2.0, Oct. 2023. https://iowngf.org/wp-content/uploads/formidable/
21/IOWN-GF-RD-Open_APN_Functional_Architecture-2.0.pdf
H. Nishizawa, J. Kani, T. Hamano, K. Takasugi, T. Yoshida, and S.
Yasukawa, “Study on Open All-Photonic Network in IOWN Global
Forum,” NTT Technical Review, Vol. 20, No. 5, pp. 18–23, May 2022.
https://doi.org/10.53829/ntr202205fa2
IOWN GF, “Open APN Architecture PoC Reference,” Ver. 1.0, Nov.
2022. https://iowngf.org/wp-content/uploads/formidable/21/IOWNGF-RD-Open_APN_Architecture_PoC_Reference-1.0.pdf
NTT press release, “NTT conducts an Open APN PoC jointly with
global optical product vendors, conducts a field test of on-demand
wavelength connection technologies, and enhances its capability todevelop photonics-electronics devices,” Nov. 14, 2022. https://group.
ntt/en/newsrelease/2022/11/14/221114a.html
NTT press release issued on June 12, 2023 (in Japanese). https://group.ntt/jp/newsrelease/2023/06/12/230612b.html

Jun-ichi Kani

Senior Distinguished Researcher, Group
Leader, Optical Access Systems Project, NTT
Access Network Service Systems Laboratories.
He received a B.E., M.E., and Ph.D. in applied
physics from Waseda University, Tokyo, in 1994,
1996, and 2005. He joined NTT Optical Network
Systems Laboratories in 1996, where heresearched optical multiplexing and transmission
technologies. He has been with NTT AccessNetwork Service Systems Laboratories since2003, where he is engaged in the research anddevelopment of optical communications systems
for metropolitan and access network applications
and currently heads the Access Systems Technology Group. He has been participating in theInternational Telecommunication Union - Telecommunication Standardization Sector (ITU-T)
and the Full Service Access Network (FSAN)
initiative since 2003.

Hideki Nishizawa

Senior Research Engineer, Supervisor, Frontier
Communication Laboratory, NTT Network Innovation Laboratories.
He received an M.S. in physics from Chiba
University in 1996 and joined NTT the same
year, where he has been engaged in research on
ubiquitous networking, photonic switching systems, and photonic transmission systems. He is amember of the Institute of Electronics, Information and Communication Engineers (IEICE).

25

Feature Articles: Recent Developments in the IOWN
Global Forum

Technical Study on IOWN for Mobile
Networks
Manabu Sugihara and Yoshitsugu Shimazu
Abstract

The IOWN for Mobile Network Task Force has been investigating technical topics related to mobile
and transport networks in the Innovative Optical and Wireless Network (IOWN), including the study of
the key requirements for transport networks in the transition from the current 5th-generation mobile
communications system (5G) to 6G, analysis of the gaps in technology hindering actualization of theuses cases aimed at by the IOWN Global Forum and proposal of solutions to them, and exploration of afuture transport network architecture that leverages the All-Photonics Network and data-centric infrastructure. This article introduces the activities of this task force.
Keywords: Technical Outlook for Mobile Networks Using IOWN Technology, PoC Reference, IMN

1. Technical Outlook for Mobile Networks Using
IOWN Technology
The IOWN for Mobile Network Task Force (IMNTF) has been studying, proposing and discussing,
together with global vendors and carriers, use cases
and technologies required for mobile and transport
networks that use IOWN Global Forum (IOWN GF)
infrastructures. The IMN-TF released “Technical
Outlook for Mobile Networks Using IOWN Technology” [1] in January 2022 and “Technical Outlook for
Mobile Networks Using IOWN Technology Advanced Transport Network Technologies for
Mobile Network” [2] in April 2023. This article
focuses on the topics that have been discussed in the
IMN-TF activities to date.
Many advanced use cases for the 5th-generation
mobile communications system (5G), including video-centric applications and latency-sensitive cases,
such as area management, telesurgery, augmented
reality/virtual reality, and industrial automation,
demand huge end-to-end bandwidth capacity, highreliability and availability, and extremely low latency
on mobile networks. Among the various technologies
that can be used to provide transport networks formobile cell sites, fiber is the best solution for fixed
network sites because of its high capacity and wideNTT Technical Review

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spread deployment. Therefore, the IMN-TF is proposing a method for implementation using fiberbased optical transport networks for mobile networks
that use the data-centric infrastructure (DCI) andOpen All-Photonic Network (Open APN) architectures.
5G can achieve high data rates using a wide bandwidth available in millimeter wave frequency bands
but requires a high-density installation of cell sites tocover a given area. Mobile-network infrastructures
are evolving toward cloud-native network function
virtualization, which opens up a variety of transport
network options and configurations. We are studying
such options and configurations from both technicaland economic perspectives, including whether they
are in line with technical trends, will improve service
deployment and provisioning agility, and will reduce
operating costs.
New services and applications enabled by 5G will
use enhanced mobile broadband, ultra-reliable low
latency communication, massive machine-type communication, and fixed wireless access technologies.
Such new services and applications generate larger
amounts of data and require latency to be extremely
low. As the volume of data in mobile networks
increases, the entire transport network, from thebackhaul to the datacenter, is required to have high26

Feature Articles

Table 1. Target fronthaul bandwidth and delay requirements of various RAN split options.
KPI

5G (2020)

6G (2030) (Projected)

E2E
Peak data rate

< 10 Gbps< 100 Gbps–1 Tbps

User plane latency (ms)1

0.1Transport: Lower Layer Split (Option 7)
Bandwidth< 25–50 Gbps

< 250 Gbps–5 Tbps

Frame delay(one-way)

0–160 µs
Fiber delay: 0–150 µs(0–30 km)
Packet delay variation (PDV):
0–10 µs(0–2 switches)

0–larger than 160 µs
Fiber delay: 0–larger than 150 µs(0–larger than 30 km)
PDV: 0–less than 10 µs

Transport: Higher Layer Split (Option 2)
Bandwidth< 10 Gbps< 100 Gbps–1 Tbps

Frame delay(one-way)

Up to ms order(up to 100 km order)

Up to ms order(up to 100 km order)

E2E: end to end
KPI: key performance indicator

Fig. 1. RAN and the APN.

capacity. People are increasingly using time-sensitive
applications, which demand ultra-low latency on theorder of milliseconds. Among the technical reports
released by the 3rd Generation Partnership Project(3GPP), 3GPP TR 38.801 [3], 3GPP TR 38.806 [4],and 3GPP TR 38.816 [5] specify eight possible radio
access network (RAN) functional split options. The
most stringent requirements considered by mobile
carriers are listed in Table 1. The IMN-TF will conduct a proof of concept (PoC) on the feasibility ofbuilding a transport-network solution that can meetthese stringent requirements (Fig. 1).
Considering that IOWN mobile networks use the
All-Photonics Network (APN) and DCI technologies,
the task force is discussing scenarios for RAN
deployment on the APN/DCI, high availability andfault tolerance enabled by the DCI and APN, and use
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cases involving elastic load balancing, which reduces
power consumption by flexibly operating base stations in response to daytime and nighttime variations
in mobile traffic.
1.1 RAN deployment scenarios on APN/DCI
In studying scenarios for RAN deployment on the
APN/DCI, it is necessary to consider the connectivity
and performance of the transport layer. The definitionof a transport-connection service typically includes
topology, a user network interface, traffic/bandwidth
profiles/characteristics, protocols, and a set of theirservice attributes. When setting up connections to
RAN functions, it is important to support the characteristics of the RAN domain, such as connections
using the standardized enhanced Common PublicRadio Interface of the Fronthaul (FH) RAN protocol.
27

Feature Articles

Fig. 2. Dynamic path switching to achieve high availability and elastic load balancing.

There are two methods for connecting each RAN
function to the APN: one that directly terminates awavelength path with an optical transceiver andanother that uses a bridging function such as a flexible bridge service.
Passive optical network (PON) technology can beused to directly connect the radio unit (RU) side to
the APN. For example, time division multiplexing(TDM)-PON can be used. However, when using
TDM-PON, it is necessary to limit the distance
between an RU and distributed unit (DU) to 10 km orless to compensate for any packet delay that exceeds
the packet delay variation (PDV) requirement (10microseconds). An advantage of using a flexible
bridge service is that multiple types of services can be
defined to support multiple quality of service levels(delay, jitter, etc.) depending on the given use case.
The task force is discussing various APN-mediatedsolutions, including a flexible bridge service, anddeveloping a PoC Reference [6] for a demonstration
model for Mobile FH over APN that satisfies bothstringent mobile fronthaul requirements and a wide
variety of base-station installation configurations.
1.2 High availability and elastic load balancing
By combining the APN, DCI and a subsystem,
namely, a RAN intelligent controller, it becomes possible for the FH network to flexibly switch DUs
within a DCI resource pool. A virtualized DU (vDU)
is a virtual node that runs on a network functions
virtualization infrastructure (NFVI) and can be freely
reconfigured on multiple NFVIs installed at different
geographic locations. We believe that we can leverage this feature to reduce power consumption. The
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associations between physical servers, DUs, and RUs
in an FH network may change as a result of external
triggers such as the failure state of the components
involved, load balancing requirements, and energy
saving requirements. High availability of RAN systems can be achieved by changing the physical associations between RUs and DUs using the APN-wavelength path-switching function when triggers such as
the following occur: traffic fluctuation or detection ofa problem such as a failure or service degradation
detected by the network. For example, all user devices(user equipment: UE) connected to an RU reconnect
to a new DU that has been reconfigured on a physically different server, or some of the RUs connected
to a DU reconnect to a physically different DU taking
the balancing of resources into account. We are
studying an elastic load-balancing function to
improve flexibility and resource-utilization efficiency in these FH networks. This function is expected to
improve the availability and power efficiency of
RAN systems. For example, by shutting down unused
DCI resources (vDUs), thus reducing their power
consumption, we can improve the power efficiency
of RAN systems (Fig. 2).
1.3 Enhanced CTI
With a view to providing end-to-end low-latency
and low-jitter services using IOWN technology, the
IMN-TF is also studying an extended cooperativetransport interface (eCTI) between a mobile networkand the APN.
When using an optical access system as a transport
network for a mobile system, it is necessary to reduce
the latency of the optical access system because the28Feature Articles

Fig. 3. eCTI overview.

allowable latency for a mobile system is very short.
Therefore, cooperative dynamic bandwidth allocation (CO-DBA), a function to reduce latency bydetermining the communication timing of the opticalaccess system in cooperation with the mobile system,
was specified. The Open Radio Access Network(O-RAN) Working Group (WG) 4 has specified a
CTI, which is the interface between the mobile system and optical access system for exchanging theinformation required for operating CO-DBA. Since
the current CTI specification cannot be applied toshort transmission time interval and mobile midhaul(MH)/backhaul (BH) that provide services demanding low latency in a mobile network, it is necessary toextend the CTI specification as an eCTI in the IOWNGF architecture. We are studying a latency-control
method with which an orchestrator coordinating themobile network and APN operations collects mobile
information, such as the aggregate traffic load, andtransfers the data to the APN controller. In implementing high-precision remote control and automatic
operation of robots and other devices, stable control
is difficult if the fluctuations (jitter) of packet arrival
time are large. Therefore, it is necessary to keep jitter,
which has not been specified as a performancerequirement in conventional networks, within a certain time frame.
To suppress delay fluctuations, we are discussing amethod for controlling the devices that make up themobile system and transport network on the basis of
information about transmission timing and the volume of transmitted data in the wireless section(Fig. 3).

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2. PoC Reference
The IMN-TF recognizes that, to support the use
cases envisioned by IOWN GF, it is necessary to satisfy the very stringent O-RAN FH requirements andthat the Open APN is a promising solution for meeting these requirements. It is therefore necessary todemonstrate the feasibility of implementing mobile
FH to which the APN is applied. While various technologies and architectures have been considered for
FH solutions, the task force considers that one of its
missions is to demonstrate the value of applying the
APN to FH, thereby having the APN recognizedwidely as a major FH solution.
The purpose of this PoC is to demonstrate, tomobile network operators and other operators whowish to offer FH as a service, the benefits of applying
the Open APN as an FH solution and the feasibility of
O-RAN key performance indicators (KPIs) and present the demonstration test results. We expect that therecognition of Mobile FH on APN as a viable andpromising solution will encourage mobile network
operators worldwide to adopt this solution, which inturn will lead to further advancement of IOWN GFrelated technologies.
There are two aspects that we want to demonstratein this PoC. The first is a benchmark test to demonstrate that the energy efficiency of the APN is higher
than that of other alternative solutions. An example ofits benefits is that the operating cost can be reduced
because the APN eliminates the conversion fromelectricity to light and vice versa. The second is todemonstrate the feasibility of implementing network
functions that can support high-availability services
29

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APN-G: APN gateway
APN-GT: APN transceiver
RF: radio frequency

Fig. 4. Network configuration for PoC Step 1.

and elastic load balancing. Elastic load balancing is aterm used in the definition of a use case in which connections of RUs to a set of vDUs can be actively anddynamically switched on the basis of actual load on
the DUs. Although directly connecting RUs to vDUs
using dedicated dark fibers without multiplexing ismore efficient than using the APN, dedicated dark
fibers do not give mobile network operators the flexibility to dynamically allocate computing and othernecessary resources to DUs in response to traffic
fluctuations. The APN, however, allows dynamic
switching of wavelength paths, which enables mobile
network operators to flexibly use computing resources at the destination in response to the current traffic
volume and other factors. We believe that the APN
will enable mobile network operators to optimize
their DU computing resources, thus reducing both
operating costs, including power costs, and base-station costs.
In this PoC, we plan to prove the feasibility of thesetwo possibilities separately in two steps.
In Step 1, we will evaluate the feasibility of Mobile
FH over APN. It will demonstrate that the very stringent O-RAN mobile FH requirements can be met.
These requirements are specified in an O-RAN
specification (O-RAN Fronthaul Interoperability Test
Specification (IOT)) and in the technical requirements in IMN documents.
In Step 2, we will evaluate the energy efficiency ofelastic load balancing. We already compared theenergy efficiency of a model in which packets are
multiplexed using layer 2/layer 3 (L2/L3) switches
over dark fiber in normal operation mode with that ofa model in which elastic load balancing is applied,and demonstrated the extent to which the latter
reduced power consumption compared with the former. We will evaluate the impact of using the APN on
services and operations. Specifically, we will verify
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the extent of end-to-end throughput degradation, thetotal time needed to switch vDU hosts, and changes
in end-to-end throughput during switching of DU
hosts to determine whether there are any servicecontinuity issues or other technical issues.
In Step 1, we plan to show that the O-RAN KPI issatisfied by collecting the latency and throughput
data of the synchronization plane, control plane, anduser plane using virtualized RAN (vRAN) devices
and APN devices in the following network configuration.
Mobile FH between RUs and DUs is located at a
certain distance apart and vDUs are concentrated at
the same site. The minimum configuration is defined
as follows. There are multiple RU sites in one cellsite. Since signals from these RUs are to be multiplexed into one fiber on the APN, at least two RU
sites are needed* (Fig. 4).
In Step 2, we plan to confirm the feasibility of theconcept of elastic load balancing in the following
network configuration. The environment in Step 1
will be extended so that, in addition to collecting data
as in Step 1, the effectiveness and usefulness of theconcept can be evaluated. In the extended environment, multiple vDUs will be deployed to allow
switching from distributed processing on multiple
hosts to centralized processing on a single host(Fig. 5).
The evaluation of two dynamic path-switching
methods for wavelength switching on the APN is
defined as follows.
Method 1 is based on optical switching. When the
traffic aggregated for each vDU varies, this method
switches the optical path between the extra network
gateway and DCI gateway so that the APN gateway*

Bandwidth per RU: 10G, 25G, or 50G; distance between RU and
DU: 2 patterns, 10–30 km.

30Feature Articles

Fig. 5. Network configuration for Step 2.

Fig. 6. Method based on optical switching.

(APN-G) will be reconfigured to optimize the number of vDUs used. More specifically, suppose thatboth RU sites and DU hosts are respectively connected. When the workload on the DU side decreases,
this method switches the optical path that has beenconnected to the lower DU host to the upper DU hostso that the upper DU host will handle the entire workload (Fig. 6).
Method 2 is based on packet switching. When the
traffic varies, the DCI gateway switches the L2/L3
path between the DCI gateway and a DU host so thatthe vDUs will be reconfigured. More specifically,
suppose that both RU sites and DU hosts are respectively connected. When the workload on the DU sidedecreases, this method switches the L2/L3 path to theupper DU host so that the upper DU host will handle
the entire workload (Fig. 7).
In Step 2, the measurement of operational data andservice level data is defined, including energy consumption, switchover time, and service-interruption
time of the Open APN and external networks between
the RU sites and DU hosts in addition to latency andthroughput included in the measurements in Step 1.
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3. Status of PoC implementation
IMN-TF member companies are holding discussions in preparation for both Steps 1 and 2, which arescheduled to be conducted up to FY2023. Member
companies are stepping up efforts for Step 1, which
includes five PoC projects that are either in process orin a preparatory stage. IMP-TF has received and discussed various proposals for detailed network configurations of Mobile FH over APN from different
companies and finally agreed on two models basedon the APN technology in accordance with the PoC
Reference. The task force members continue to discuss whether the proposed solutions are promising
and will clarify possible use cases and benefits. Subsequent PoC projects and evaluation will then be carried out.
For Step 2, the task force aims to discuss detailed
use cases, operating-condition specifications, KPIs,
and data to be collected and revise the PoC Reference
toward the second half of FY2023.

31

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Fig. 7. Method based on packet switching.

4. NTT Group’s activities in IMN-TF
NTT Group’s activities in the IMN-TF are twofold.
First, NTT laboratories are proposing to use theresults of their research on coordinated optical wireless control technology [7]. Mobile systems, whichconstitute wireless sections, use a wired network forthe transport network that establishes connections
between base-station devices and connections withthe core network. However, mobile systems and thetransport network have conventionally been designed,
constructed, and operated independently of eachother. Therefore, they cannot operate as a single unit
capable of dynamically changing the operation of thetransport network in accordance with the state of themobile systems. To provide services that require low
latency in a mobile network, it is necessary to control
and reduce latency through optical paths and DCI
gateways on the basis of mobile information provided by network devices, such as DUs. The function for
reducing latency is specified as CTI by O-RAN WG
4. NTT laboratories have extended the CTI specification to define an eCTI for the IOWN GF architectureand studied a method with which the APN controller
reduces both end-to-end latency and jitter by obtaining mobile information from CUs/DUs through theeCTI. On the basis of this study, NTT laboratories areleading discussions for producing a proposal on alatency/jitter-reduction method and for demonstrating its feasibility.
Second, NTT DOCOMO has been operating andsupporting the IMN-TF as a co-coordinator sinceApril 2022. On the strength of its experience in thecommercial deployment of Open RAN and in the

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promotion of vRAN through OREX, and through its
communication with other task force members, NTT
DOCOMO is leading efforts to ensure smooth progress of task force activities. Examples are formulating
activity plans for the IMN-TF, setting goals and targets for each topic, proposing agendas and summarizing discussions held in member meetings, and inputting the trends of international standardization bodies
such as 3GPP and O-RAN Alliance. The IMN-TF
will continue to work on solving problems in themobile domain, including the actualization of elastic
load balancing.
References
[1]

[2]

[3]

[4]

[5]
[6]
[7]

IOWN Global Forum, “Technical Outlook for Mobile Networks
Using IOWN Technology,” Ver. 1.0, 2022. https://iowngf.org/wpcontent/uploads/formidable/21/IOWN-GF-RD-Technical-Outlookfor-Mobile-Networks-1.0-1.pdf
IOWN Global Forum, “Technical Outlook for Mobile Networks
Using IOWN Technology - Advanced Transport Network Technologies for Mobile Network,” Ver. 1.0, 2023. https://iowngf.org/wpcontent/uploads/formidable/21/IOWN-GF-RD-IMN-PHSE2-1.0.pdf
3GPP TR 38.801: Study on new radio access technology: Radio
access architecture and interfaces, https://portal.3gpp.org/
desktopmodules/Specifications/SpecificationDetails.
aspx?specificationId=3056
3GPP TR 38.806: Study of separation of NR Control Plane (CP) andUser Plane (UP) for split option 2, https://portal.3gpp.org/
desktopmodules/Specifications/SpecificationDetails.
aspx?specificationId=3307
3GPP TR 38.816: Study on Central Unit (CU) – Distributed Unit
(DU) lower layer split for NR, https://portal.3gpp.org/desktopmodules/
Specifications/SpecificationDetails.aspx?specificationId=3364
IOWN Global Forum, “Mobile Fronthaul over APN PoC Reference,”
Ver. 1.0, 2022. https://iowngf.org/wp-content/uploads/formidable/21/
IOWN-GF-RD-MFH_over_APN_PoC_Reference_1.0.pdf
T. Hatano, Y. Sakai, K. Asaka, and T. Shimada, “Low-latency Function-dedicated Network Providing Sustained and Stable Services,”
NTT Technical Review, Vol. 21, No. 12, pp. 43–49, 2023. https://doi.
org/10.53829/ntr202312ra2

32

Feature Articles

Manabu Sugihara

Senior Manager, IOWN Development Office,Research and Development Planning Department, NTT Corporation.
He received an M.E. in informatics and computer engineering from the University of ElectroCommunications, Tokyo in 1998 and joined NTT
DOCOMO the same year. He was engaged in thedevelopment of wireless networks, voice/packet
switching equipment, subscriber database systems, and NFVIs. He has been with IOWN
Development Office in NTT since 2021 and isengaged in activities of the IOWN Global Forum
IMN-TF.

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Yoshitsugu Shimazu

Vice President of Innovative Technology
Office, Technology Planning, NTT Corporation.
He received a B.E and M.E from Kyoto University in 1997 and 1999. He joined NTT
DOCOMO in 1999 and has over 21 years ofexperience in development of RAN equipment
for commercial network. He was awarded theMaejima Hisoka Award in 2017, and Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science andTechnology in 2020. He has been director of
Innovative Technology Office, Technology Planning, NTT since 2020 and vice president since2023. He is a member of the Institute of Electronics, Information and Communication Engineers(IEICE) of Japan.

33

Feature Articles: Recent Developments in the IOWN
Global ForumIOWN Data Hub to Become a Reality
Kunihiko Minamihata, Tomohiro Inoue,and Kazuyuki Takaya
Abstract

The IOWN Global Forum is working on the social implementation of the Innovative Optical and Wireless Network (IOWN) technology. This article introduces the progress of the storage service study in the
IOWN Global Forum, focusing on the newly published IOWN Data Hub Functional Architecture version 2.0 and the Proof of Concept Reference and NTT laboratories’ activities related to the IOWN Data
Hub.
Keywords: storage, database, virtual data lake

1. Background of the need for IOWN Data Hub
Integrating the real and virtual worlds and feeding
the results of simulations in the virtual world back to
the real world in real time can provide many benefits,
such as the ability to detect and quickly respond tohazards and maintain a comfortable environment
with minimal changes. However, to achieve this integration, it is necessary to synchronize in real time thedata and behavior of a vast number of objects sensed
in the real world with those in cyberspace. Due totheir high latency, current networks cannot synchronize vast amounts of data over a wide area in realtime, making it difficult to construct a high-definition
digital twin that covers a vast space. To solve thisproblem, we need the IOWN Data Hub (IDH), a new
data-sharing platform built on the Open All-Photonic
Network (APN) and data-centric infrastructure(DCI), which are both infrastructures of the Innovative Optical and Wireless Network (IOWN). This
article focuses on the update of the IDH architecture
document and proof of concept (PoC) activities
undertaken to enable the IDH.
2. IDH activities at the IOWN Global Forum
In January 2022, IOWN Global Forum members,
including NTT, Oracle, and NEC, collaborated todevelop and release IOWN Data Hub Functional
Architecture version 1.0. For the basic mechanism
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and concept of the IDH, refer to “Study of Storage
Services at IOWN Global Forum” [1] that can befound in the NTT Technical Review. After the releaseof the above architecture document, the IOWN
Global Forum held a series of discussions towardsocial implementation, and in July 2023, updated the
document to release the IOWN Data Hub Functional
Architecture version 2.0 [2]. The main updates are as
follows:(1)	Specific description of use-case requirements:
Identification of data types, bandwidth
requirements, etc. for each use case presented
in the Cyber-Physical System (CPS) and AI(artificial intelligence) Integrated Communications (AIC) use-case documents [3, 4].
(2)	Identification of inherent gaps: Gap analysis
based on more specific implementation models.
Some of the requirements for the use cases
described in update (1) are listed in Table 1. Thesefuture use cases will need to meet diverse anddemanding data processing and sharing requirements. For example, to meet real-time requirements,
it is necessary to process data as-is without any conversion, close to the original data. To handle a large
number of data flows, it is necessary to significantly
improve distributed data management engines so thatthey can operate over ultra-high-speed, high-quality
networks. Robust data security and data-usage control mechanisms will be required to enable fast and34

Feature Articles

Table 1. IOWN Global Forum use cases and high-level data requirements.
Expected requirements
Use case

Data collection
bandwidth

Producer-consumer
latency

Data Producers• Video cameras:
1,000 per monitored area (e.g., building) x
100–10,000 monitored areas
Continuously sending data
• LiDAR sensors:
1,000 per monitored area (e.g., building) x
100–10,000 monitored areas
Continuously sending data
Data Consumers• Security officers:
Up to 1,000 per monitored area
Receiving alerts when detected• Security monitors:
Up to 50 per monitored area
Displaying the selected cameras• 45–60 Mbit/s percamera (assuming
Full HD motion
JPEG)• 600–800 camerasi.e., 27–48 Gbit/s perbuilding• Thousands or
millions of buildings(depending upon therequired control)

From data collection
through analysis toalerting: 1 sec, ideally
100 ms• Robot/drone’s
high-definition (8K)
cameras• Robot/drone’s
sound/odor sensors

Data Producers• Machines and/or robots
Up to 10,000 per factory
Continuously sending data when they are in
operation
Data Consumers• Machines and/or robots
Up to 10,000 per factory
Receiving control signals when required• Factory Engineers
Up to thousands
Receiving alert signals and other information
when required• 2.35 Gbit/s per
robot/drone

From data collection
through analysis tofeedback controls:
10 ms, sub-second, ora second (depending
upon the use casescenario assumed)• Sensor data fromprosumer• External data
sources (weather
data, human flow
data, etc.)

Data Producers• Prosumer devices (e.g., smart meters, electricvehicles, etc.) and power grid systemequipment (e.g., switchgear, transformer, etc.)
More than 100,000
Continuously sending data
Data Consumers• Prosumer devices and power-grid-systemequipment
More than 100,000
Receiving control signals when required• 24 Tbit/s (received
from data producer)

From data collection
to display:
50 ms
From data collection
to analysis andfeedback control:
200 msData type

Data producers and consumers

Area
management
security• Video cameras• LiDAR sensors

Industry
management
Remote factory
control

Smart-gridmanagement
Renewableenergy
optimization• 128 Pbit/s (datatransmission fromelectric vehicles in2030)• 3.2 Gbit/s (otherdata sources)

HD: high definition
JPEG: Image compression formats created by the Joint Photographic Experts Group.
LiDAR: light detection and ranging

reliable data exchange between multiple parties.
Update (2) identified gaps in the computing environment as well as problems in datacenters (DCs) andmodels for data sharing and processing models thatmake up the computing environment.
2.1 Fundamental problems in DCs
The current networks and DC technology have several fundamental problems in the following areas.
These must be solved if we are to build IDH services
that meet the use-case requirements (Fig. 1).
(1) Inter-DC network quality
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The network quality between DCs used in today’s
cloud is focused on current use cases. Since packet
reordering and loss occur in networks, the Transmission Control Protocol (TCP) is used more frequently
than other protocols, such as the User Datagram Protocol (UDP), to ensure reliability. These networks do
not provide sufficient performance for the workloads
of geographically distributed databases and storage
systems that are required by the use cases in the
IOWN era.
(2) Intra-DC network quality
The quality of the networks used by hyperscale
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Feature Articles

Fig. 1. Origins of gaps in today’s technology landscape.

DCs that make up a cloud are not high enough. For
example, one-way latency can exceed 1 ms, a latency
sufficiently high to cause packet loss to exceed 1%during severe network congestion. The bandwidth issimilarly unstable. This is essentially due to oversubscription, a scheme that allows reservation of bandwidth beyond the capacity of the network devices.
Therefore, the network that connects computing
resources in a DC cannot guarantee all the bandwidth
allocated to individual resources.
(3) Storage performance
To ensure data persistence, data are typically synchronized across multiple servers. However, synchronization requires a large workload, rendering
performance very unstable. Thus, storage systems
that are connected via today’s cloud-based storage
area networks tend to be slower than directly connected storage devices. For example, the responsetime of storage systems can exceed dozens of milliseconds, making such systems unsuitable for typical
database workloads or redundant storage systems.
(4) Data-sharing performance
In cases where data are processed cooperatively
across multiple servers, a certain amount of dataexchange is required between servers, for example, toredistribute data. This exchange significantly reduces
overall performance. To speed up such data servers,
some implementations connect servers using remote
direct memory access (RDMA) fabric connections.
However, since the use of RDMA in production environments imposes strict requirements, such as nopacket loss and no packet reordering, RDMA is used
only for very limited purposes in today’s cloud environments.
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(5) Accelerator usage
Accelerators, such as graphics processing units(GPUs) and field programmable gate arrays (FPGAs),
have the potential to achieve high performance, costeffectiveness, and energy efficiency at least 10 times
greater than software-based processing on generalpurpose central processing units (CPUs). However,such an accelerator must be deployed within eachserver and cannot directly access external clients forthe purpose of streamlining data loading. Therefore,
with current network and DC technologies, it is notpossible for multiple general-purpose computing
resources to share accelerator resources at high speed
and with low overhead.
2.2 T oday’s implementation model and inherent
gaps
Considering the aforementioned issues, we must
accept the following constraints if we are to use
today’s technology to provide data services such as
the IDH.
(1) Completion of data processing within one place
If processing efficiency could drop sharply due topoor quality of the network that connects DCs, itwould be difficult to implement geographically distributed data services. Therefore, current data-processing services are designed to be implemented
within a single DC or within nearby availability
zones. In fact, today’s clouds are an aggregation ofsuch services. The size of cloud DCs has become soenormous that the number of available cloud regions
is very limited, 30 or so at most worldwide. Thismeans that, regardless of where data were generated,
all data must be transferred to one of the cloud DCs
36

Feature Articles

and all data processing must be completed there,
making the system’s energy use highly inefficient.
(2)	Asynchronous data replication as a foundation
to build a scalable transactional distributed relational databaseIn building a scalable transactional relational database (RDB) system, it is a common practice to place
replicated read-only data near each RDB server. Suchdata replication tends to be asynchronous because the
network is slow. To reduce the load imposed on slow
networks by data replication, often only the transaction or change logs, rather than the data, are propagated. This improves performance but requires reconstruction of table data from the log data on eachserver, which inevitably increases the system cost andpower consumption.
(3)	Sharded data processing to build a scalable keyvalue store, message broker, and/or analytical
distributed RDB
Sharding is a technology for reducing responsetime and improving scalability by grouping related
data together and distributing it across multiple databases. It is used to build scalable systems, such as a
key-value store (KVS). However, it does not eliminate data transfer needed for data relocation andserver-to-server communication. Rather, the volume
of such data transfer and communication may
increase in advanced digital transformation (DX)services that need to handle data from many different
angles. Since sharded systems require a certain
amount of data transfer between scale-out and scalein operations, data services in the cloud today experience constraints on dynamically changing scalability.
(4) Usage of a cache layer
The constraints imposed by low-speed networks
and storage systems often make it necessary to manage data on a process-by-process basis and rely heavily on asynchronous distributed processing. To
streamline such implementations, various cacheddata management services are provided in today’s
cloud. However, such services increase end-to-end
latency and cause the same data to be copied unnecessarily multiple times in the cloud, which is undesirable in terms of cost and energy consumption.
(5) Accelerator in use only in a laboratory
One possible approach to solving the aforementioned problems is to use accelerators, such as GPUs
and FPGAs, to speed up queries and other data processing in distributed RDBs. Software has beendeveloped and validated for such purposes, but in
actual practice, the use of such software rarely
improves and often diminishes performance and costNTT Technical Review

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effectiveness. This is mainly due to the need to preload data at the startup of the accelerator.
The IDH must be designed to address the fundamental and inherent challenges of today’s cloud system and must be further developed to adapt to use
cases of the wide-area and real-time CPSs that will be
increasingly demanded in the future. To this end, it isnecessary to verify the IDH iteratively in actual use
cases and reflect the results to refine the required
functions and design methodology of the IDH.
3. PoC activities on the IDH
In October 2022, the IOWN Global Forum formulated the IOWN Data Hub PoC Reference [5] to help
implement the IDH. The use of the Open APN will
result in a quantum leap in the speed of hybrid andmulti-cloud connections, which in turn will cause ashift from concentration in hyperscalers to the use ofenterprise DCs and edge clouds. Thus, it will be necessary to innovate data sharing architecture so that it
can accommodate this shift. The IDH disaggregates
the functions and processing that have previously
been executed by hyperscalers in the central cloudand relocates them to edge clouds. To validate anddeploy the IDH architecture, in which connections
are set up by the Open APN and DCI, in many use
cases, the IOWN Global Forum has released this PoC
Reference and is seeking participation from a wide
range of organizations, not limited to IOWN Global
Forum members.
3.1 The IDH PoC ReferenceThis PoC Reference has been formulated to validate the IDH architecture that meets the stringent
requirements of various DX services. Smart factory,
smart grid, and metaverse have been selected as usecase examples and five PoC scenarios have been
defined.
To build a metaverse service, for example, it istypically necessary to collect information about theparticipants, represent them as avatars in the virtual
space, and allow the avatars to interact with eachother. Thus, provision of a high-quality metaverse
service requires the following.
•	Collect motion data from up to millions of participants and reflect them in the movements of
their avatars in cycles of dozens of milliseconds.
•	Move avatars in the virtual space, which contains many virtual buildings and other structuralelements, and enable them to communicate witheach other.
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Feature Articles

PoC Scenario 5
New frontend implementation supporting lowlatency responses and efficient geo-distributed
processing

PoC Scenario 1
Frontend-to-Data Service PUT Communication
Acceleration with Open APN

PoC Scenario 3
Data Service-to-Data Service Communication
Acceleration with Open APN
PoC Scenario 2
Data Service-to-Frontend GET Communication
Acceleration with Open APN
PoC Scenario 4
Elastic high-speed shareable storage with DCI

Fig. 2. Geo-distributed IDH adoption model and IDH PoC scenario mapping.

•	Render virtual space scenery from each avatar’s
perspective with motion-to-photon latency ofless than dozens of milliseconds.
To demonstrate the IDH architecture for supporting
such use cases, the PoC Reference defines a test environment that reflects the geographically distributed
deployment of assumed IDH services and identifies
the items that PoC projects should validate (Fig. 2).
In this model, a subgroup of front-end servers of the
IDH architecture is deployed at a regional edge centerto provide low-latency services to connected Internetof Things (IoT) devices. The data service servers andstorage servers, which are part of the IDH architecture, are deployed at remote DCs or the central cloudto support data persistence and usage.
On the basis of this model, the PoC Reference
defines the following five PoC scenarios:•	Scenario 1: Frontend-to-Data Service PUT Communication Acceleration with Open APN•	Scenario 2: Data Service-to-Frontend GETCommunication Acceleration with Open APN•	Scenario 3: Data Service-to-Data Service ComNTT Technical Review

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munication Acceleration with Open APN•	Scenario 4: Elastic High-speed Shareable Storage with DCI•	Scenario 5: New frontend implementation supporting low-latency responses and efficient geodistributed processing
For each scenario, the PoC Reference describes an
overview, required functions, variable conditions,and expected benchmarks to enable the readers toproceed with their PoC projects (Table 2).
IOWN Global Forum member companies are currently conducting PoC projects for their respective
scenarios on the basis of this PoC Reference. Thus,
the IDH is making steady progress toward its social
implementation.
4. Activities in the NTT GroupTo contribute to the implementation of the IDH, theNTT Software Innovation Center is developing virtual data lake, which is defined as a set of functionsin the IDH reference architecture.
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Feature Articles

Table 2. Benchmark requirements for each scenario.
Selected features

Variable conditions

Expected benchmark• Effect of the network type,latency, jitter, bandwidth,
packet loss, and packet orderchange• Network-protocol parameters• Data-object size and presence/
absence of data compression• Throughput per unit system
resource• Energy consumption per unit
system resource• Effect of the network type,latency, jitter, and bandwidth• Network-protocol parameters• Data-object size
• Ratio of relevant data

• Time for required datatransfer

PoC Scenario 3
Data Service-to-Data Service
Communication Acceleration
with Open APN• Inter-server communications over
Open APN• Continuous data ingestion and data
• Pull-access of data
• Push-delivery of data
• Synchronous data replication acrossmultiple data-service servers ofmessage broker, distributed RDB,
and KVS• Scalability• Effect of the network type,latency, jitter, and bandwidth• Effect of the transaction size
• Effect of the data-record size

• Data-hub response time andjitter• Throughput per unit system
resource• Energy consumption per unit
system resource• Scaling factor

PoC Scenario 4
Elastic High-speed Shareable
Storage with DCI• Establishment of communication
paths between data-service servers
and storage servers, which may go
through the gateway server, madeby DCI• Usage of standard protocols such asiSCSI• Shared storage• Scalability• Effect of the network type,latency, jitter, and bandwidth• Effect of the data-block size
• Random/sequential access• Ratio of read/write operations• Storage system topology• Storage-system responsetime• Throughput per unit system
resource• Energy consumption per unit
system resource• Scaling factor• Data-hub performance

PoC Scenario 5
New frontend implementation
supporting low-latency
responses and efficientgeo-distributed processing• Data Ingestion through Open APN• Convergence of message broker
and other data hub services• In-memory-based data processing• Memory-space sharing acrossmessage-broker (buffering) role andother data-hub roles• Continuous data ingestion andsubsequent data processing• Resource controls (both test
environments)• Scalability• Effect of the network type,latency, jitter, and bandwidth• Effect of the transaction size
• Effect of the data-record size

• End-to-end response timeand jitter• Throughput per unit system
resource• Energy consumption per unit
system resource

PoC Scenario 1
Frontend-to-Data Service PUTCommunication Acceleration
with Open APN• PUT Communications over OpenAPN
• Data preprocessing before datatransfer• Federation function in cloud DC
PoC Scenario 2• Get Communications over Open
Data Service-to-Frontend GET
APNCommunication Acceleration• Data filtering and preprocessing inwith Open APN
the on-premise DC

There are various stakeholders in both the realworld and virtual world, which is built by Digital
Twin Computing. To enable the feedback between thetwo worlds to loop in real time, data must not only betransmitted at high speed but also be securely
exchanged between stakeholders who have different
standpoints. Therefore, it is essential to enable stakeholders to handle the latest data as if they were athand, while ensuring permanent governance of theshared data.
The virtual data lake being developed by NTT Software Innovation Center virtually aggregates andcentralizes omnipresent data that are managed by
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different organizations and geographically dispersed
across multiple locations, enabling data users toacquire and use only the needed data efficiently andon-demand. For this purpose, the virtual data lake
provides functions that enable data users to search forand discover the data they need from among a vast
amount of data based on metadata (semantic and format information of data) and functions that maintain
governance by enabling data users to display and use
only those items of data they are permitted to use
based on the policies set by data providers. These
functions enable organizations to mutually use a large
volume of widely varied data quickly, easily, securely,
39Feature Articles

and reliably across organizational boundaries.
To make the IDH platform fit for practical use, wewill continue to conduct demonstration tests of theplatform by referring to the IDH PoC Reference andother reference materials.

References[1][2]

5. Future development
As a “database is a network” platform that supports
Digital Twin Computing that runs on the Open APN
and DCI, the IDH is expected to be used for missioncritical use cases such as wide-area automated driving. Together with many partners, NTT will verify
various IDH implementation models that satisfy therequirements imposed by use cases in the IOWN era
and promote its social implementation.

Kunihiko Minamihata

Senior Manager, IOWN Development Office,R&D Planning Department, NTT Corporation.
He received a B.E. and M.E. in informationand knowledge engineering from Shizuoka University in 1998 and 2000. He then joined NTT
WEST Corporation in 2000 as a system andsecurity engineer for corporate business. He is
engaged in spreading IOWN technologies andsupporting IOWN Global Forum operations in
his current position.

[3]
[4]
[5]

T. Inoue, “Study of Storage Services at IOWN Global Forum,” NTT
Technical Review, Vol. 20, No. 5, pp. 32–36, 2022. https://doi.
org/10.53829/ntr202205fa4
IOWN Global Forum, “Data-Centric Infrastructure Functional Architecture,” Ver. 2.0, 2023. https://iowngf.org/wp-content/uploads/
formidable/21/IOWN-GF-RD-Data_Hub_Functional_Architecture2.0.pdf
IOWN Global Forum, “Cyber-Physical System Use Case Release-1,”
Ver. 1.0, 2021. https://iowngf.org/wp-content/uploads/formidable/21/
IOWN-GF-RD-CPS_Use_Case_1.0.pdf
IOWN Global Forum, “AI-Integrated Communications Use Case
Release-1,” Ver. 1.0, 2021. https://iowngf.org/wp-content/uploads/
formidable/21/IOWN-GF-RD-AIC_Use_Case_1.0.pdf
IOWN Global Forum, “IOWN Data Hub PoC Reference,” Ver. 1.0,
2022. https://iowngf.org/wp-content/uploads/formidable/21/IOWNGF-RD-IDH-PoC-Reference_1.0.pdf

Kazuyuki Takaya

Senior Research Engineer, Supervisor, Social
Information Sharing Research Project, NTT
Social Informatics Laboratories.
He received an M.E. from Waseda University,
Tokyo, and joined NTT in 2000. He is engaged in
the research and development of technologies
and platforms for data sharing.

Tomohiro Inoue

Director, Data Sharing Infrastructure Project,
NTT Software Innovation Center.
He received a B.E. and M.E. from the University of Tokyo in 1999 and 2001. He joined NTT
in 2001 and is currently engaged in the researchand development of data hubs, trusted datasharing infrastructure, and global data-spaceinterconnection as the leader of Information
Sharing Architecture Group.

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40

Feature Articles: Recent Developments in the IOWN
Global Forum

DCI Architecture Promoted by the
IOWN Global Forum
Hiroshi Yoshida
Abstract

The IOWN Global Forum has proposed an information and communication technology (ICT) infrastructure, called data-centric infrastructure (DCI), that leverages the high-speed and low-latency featuresof the Innovative Optical and Wireless Network All-Photonics Network (IOWN APN). This article
describes the DCI on the basis of the Data-Centric Infrastructure Functional Architecture version 2.0
released by the forum in March 2023 and explains the advantages of the DCI in tackling challenges inscalability, performance, and power consumption that confront current ICT infrastructures. It is hopedthat this article will help readers deepen their understanding of the DCI.
Keywords: data-centric, IOWN Global Forum, DCI

1. Introduction
An article entitled “Data-centric Infrastructure for
Supporting Data Processing in the IOWN Era and Its
Proof of Concept” [1], in the January 2024 issue of
this journal, presented an overview of the data-processing infrastructure and accelerator in the datacentric infrastructure (DCI), a new information andcommunication technology (ICT) infrastructure proposed by the forum, and described its proof of concept activities using video analysis as a use case.
As a follow up to the above issue, this article
explains the overall picture of the DCI with a focus
on the Data-Centric Infrastructure Functional Architecture version 2.0 [2] released by the IOWN Global
Forum in March 2023. We hope that readers will
peruse this article together with the Feature Articles
on efforts toward the early deployment of IOWN in
the January 2024 issue to deepen their understandingof the DCI.
2. Challenges confronting current
ICT infrastructures
2.1 Challenges in scalability
ICT infrastructures need to support various types ofdata processing with different requirements. For
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example, online transaction processing needs to
respond to a large number of inquiries while data
batch processing must handle vast amounts of data.
The data-processing requirements of ICT infrastructures can also change rapidly over time. For example,
an event, such as a sale, generates a large number ofaccess attempts to an Internet shopping site, requiring
ICT infrastructures to respond to these changes
within minutes or hours. Therefore, ICT infrastructures must have sufficient scalability to flexibly
respond to such changes in demand.
2.2 Challenges in performance
Some types of data processing, such as communicating the movements of individual participants in a
virtual space to the people around them or processing
high-speed transactions in financial applications,must meet stringent response-time requirements.
Current ICT infrastructures cannot adequately satisfy
such exacting requirements, especially in data transfer.
2.3 Challenges in energy consumption
Today’s ICT infrastructures have various bottlenecks. For example, if data transfer is a bottleneck,the central processing unit (CPU) consumes most of
its processing power simply waiting for data transfer.
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Feature Articles

Individual
application

Individual
application

Individual
application

Creation of programmable end-to-end data pipeline

DCI

Provision of fast, reliable, low-latency network connectivity

Open APN

Fig. 1. Overview of ICT infrastructure centered on DCI.

It has become common to allocate processing toaccelerators, which are adept in areas that are different from those of the CPU, such as graphics processing units (GPUs), which specialize in image processing to achieve high-speed processing, and data processing units (DPUs), which specialize in specifictypes of computation such as network processing andsecurity processing. Efficient use and appropriaterole sharing of computing resources can optimize thepower efficiency of the entire ICT infrastructure.
3. The DCIThe DCI is a new ICT infrastructure proposed by
the IOWN Global Forum to address these challenges.
Figure 1 gives an overview of the ICT infrastructure
centered on the DCI. In the hierarchical structure ofthis ICT infrastructure, the Open All-Photonic Network (APN) is located at the bottom and applications
at the top. Leveraging the high-capacity, low-latency
network environment of the Open APN, the DCI provides programmable end-to-end data pipelines tohelp applications perform.
This article first explains the concepts of the OpenAPN and data pipeline then describes how the DCI
helps applications perform.

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3.1 What is the Open APN?
The Open APN is a high-speed network that consists entirely of optical communication. It is characterized by its ability to provide a high-capacity network with low latency, particularly with predictablelatency. Therefore, it can transfer data between various devices connected to the network as if thesedevices were close to each other, regardless of theirlocations and the distances between them. Moreinformation on the Open APN and NTT’s related
activities are given in the article, “Activities for
Detailing the Architecture of the Open APN and Promoting Its Practical Application,” in this issue [3].
3.2 What is a data pipeline?
A data pipeline is a uniform stream that executes
functions, such as acquisition, processing, conversion, and presentation of the data required by various
applications. Figure 2 shows an example of a data
pipeline for a system that aggregates and analyzes
surveillance-camera footage on the basis of metadata[4]. In this example, the footage from a surveillancecamera is sent to an analysis server, which analyzes
information contained in the metadata, such as information about what is captured in the video. The metadata are sent to the analysis server for the purpose ofdata aggregation, and raw video data are stored instorage units. Using a terminal, analysts can analyze
42Feature Articles<Camera><Server><Server><Analyst>

SurveillancecameraAnalysisserverAnalysisserverTerminal

D1
Filming

D2
Video analysis
Metadata
generation

D4
Display ofanalysis results
and video data

Metadata
aggregation<Video-data storage unit>
D3

D5
Raw video data

Fig. 2. Example of a data pipeline of a system that aggregates and analyzes surveillance-camera footage on the basis of
the metadata.

data on the basis of the metadata and refer to theactual footage data in the storage units. In Fig. 2, eachoval represents data processing, i.e., a set of autonomous actions, such as data collection and analysis. A
process is executed by a functional node, represented
with a rectangle, which exists outside the process. A
database/storage, represented with a drum, is typically a file system or database. It is a function forstoring data. Connecting these are data flows, which
are functions to transfer data to data processing or
storage. The IOWN Global Forum has defined thisrepresentation of a data pipeline as a data-pipeline
diagram [4]. Therefore, a data pipeline is an abstraction of resources used to enable an application tofunction.
4. Various DCI resources
How does the DCI create a data pipeline? Before
answering this, let me explain how the DCI manages
various resources.
4.1 F
 unctional cards, physical nodes, and DCIclusters
A schematic diagram of the various resources managed by the DCI is shown in Fig. 3.
As mentioned above, data processing refers to thefunction of collecting or analyzing data in the data
pipeline and is typically implemented using CPUs.
GPUs, which specialize in image processing to
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achieve high-speed processing, and DPUs, which
specialize in specific types of computation, such as
network processing and security processing, havebeen attracting attention. Storage is implemented
using solid-state drives (SSDs) and hard disk drives.
In the DCI, data processing and storage are classified into two categories: host board and functionalcard. A host board typically consists of a CPU andmemory unit. It corresponds to a motherboard in a
typical server. Functional cards are other components, such as GPUs, DPUs, network interfaces, andstorage units. A functional card corresponds to an
expansion board in a general server, such as a network interface controller (NIC) or a graphics card, or
to a storage unit such as an SSD. A DCI physical nodeconsists of a host board and multiple functional cards.
An intra-node interconnect connects the host board
and functional cards within a DCI physical node.
Peripheral Component Interconnect Express (PCIe),
which is widely used in servers, is an example of an
intra-node interconnect. However, more flexible
standards, such as Compute Express Link (CXL), arebeing studied.
A DCI cluster is a computing infrastructure consisting of multiple physical nodes. It also includes thecharacteristic mechanisms of an inter-node interconnect and DCI gateway.
The inter-node interconnect is a network that connects DCI physical nodes. Although general clusters
also have a network that connects servers that make43

Feature Articles

DCI physical node #1
Host board

Functionalcard

Directconnection

Other DCI
clusters

Directconnection

Open
APN

Functional card

Functionalcard

DCI physical node #2
DCI
gateway

Host board

Functionalcard

Directconnection

Inter-node interconnect

Intra-node interconnect

Intra-node interconnect
Directconnection

Functional card

DCI cluster

Fig. 3. Schematic of various resources managed by the DCI.

up the cluster, the inter-node interconnect differsfrom such a network in that some functional cards candirectly access inter-node interconnects. Functionalcards that can directly access inter-node interconnects are called “network-capable” functional cards.
Such a card can directly transfer data to and fromfunctional cards and host boards residing in otherphysical nodes without going through the intra-nodeinterconnect of the physical node to which it belongs.
An NIC is of course a network-capable functionalcard. It is assumed that some GPUs and storage units
and some functional cards are also network-capable.
The DCI gateway interconnects DCI clusters. It isconnected to other DCI clusters via the Open APN.
Network-capable functional cards can also directly
access the DCI gateway and transfer data to and fromfunctional cards belonging to other DCI clusters via
the Open APN at high speed.
4.2 L ogical service node and data-pipeline implementation
How a DCI cluster can create a data pipeline for an
application is explained. To create a data pipeline, a
DCI cluster selects functional cards and host boards
within itself and builds a logical service node (LSN)
from them.
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Vol. 22 No. 2 Feb. 2024

If an LSN consists of elements within a single
physical node, all data flows in a data pipeline can betransferred via the intra-node interconnect in thatphysical node. However, if the LSN spans multiple
physical nodes, an inter-node interconnect is required
to transfer the data flow. A data pipeline can be created using multiple LSNs that belong to different DCI
clusters. In this case, data flows across LSNs must go
through a DCI gateway.
Figure 4 shows an example of a data-pipeline configuration. This DCI cluster has selected the functional cards shown in yellow, i.e., Functional cards A,
B, and C, to configure the LSN. Not being networkcapable, Functional Card A cannot directly connect tothe inter-node interconnect. Consequently, it connects to the inter-node interconnect via the intra-nodeinterconnect and Functional Card X.
Functional Card B of DCI physical node #2, however, is network-capable. Therefore, the inter-nodeinterconnect can be directly connected to Functional
Card B. Functional Card C is also network-capableand is connected to the DCI gateway. This means
Functional Card C can connect to another LSN in
another DCI cluster via the DCI gateway.
As described above, a feature of the DCI is the ability to configure flexible data pipelines across DCI
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Feature Articles

DCI physical node #1
Functional Card X

Host board

Directconnection

Functional card

Other DCI
clusters

Inter-node interconnect

Intra-node interconnect
Open
APN

Functional Card A

DCI physical node #2

DCI
gateway

Host board

Intra-node interconnect
Directconnection
Functional Card C

Functional Card B

Directconnection

DCI cluster
Another LSN

LSNOpen APN

Function Card A

Functional Card X

Data flow via
intra-node interconnect

Functional Card B

Data flow via
inter-node interconnect

Functional card

Functional Card C
Data flow via
intra-node interconnect

Data flow via
DCI gateway andOpen APN

Fig. 4. Example of data-pipeline configuration.

physical nodes and DCI clusters.
5. Challenges with the DCI and solutions
How the DCI creates a data pipeline has been
described. The following describes how the DCI
solves the challenges in scalability, performance, andpower consumption mentioned earlier.
5.1 Addressing challenges in scalability
In conventional ICT infrastructures, computing
resources and wide-area networking resources fordata transfer have evolved independently, making
flexible scaling across physical nodes and clusters
difficult. With the DCI, however, network-capablefunctional cards are directly interconnected via internode interconnects, thus eliminating data-transfer
bottlenecks. LSNs in different DCI clusters can also
be easily integrated via DCI gateways. The integration of resources across physical nodes and clusters inthis way makes for high scalability.
5.2 Addressing challenges in performanceWith the DCI, network-capable functional cards are
directly interconnected via inter-node interconnects.
Thus, data can be transferred between them at
extremely high speed without going through a CPU.
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Because data can also be transferred across DCI clusters at high speed via the Open APN, applications canhave sufficient response performance with stringent
response-time requirements.
5.3 Addressing challenges in energy consumption
With the DCI, because there are few bottlenecks indata transfer, CPUs are not kept waiting needlessly
for data transfer. Accelerators, such as GPUs andDPUs, can also be selected flexibly depending on thecomputing requirements. This improves computingresource utilization and makes it possible to optimize
overall system energy consumption.
6. Key Values and Technology Evolution
Roadmap and future development of the DCI
Finally, how DCI-related technologies will evolveon the roadmap is described by referring to the Key
Values and Technology Evolution Roadmap [5]released by the forum in August 2023.
The current unit used for computing resource allocation management is a server. In Phase 2, the unit
will be decreased in granularity to an element, such asa host board or functional card. In Phase 2 as well,
network-capable functional cards will be able todirectly transfer data between GPUs and DPUs.
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Feature Articles

Table 1. IOWN computing development roadmap.
Element

Phase 1 (now)Phase 2 (3–5 years from now)

Phase 3 (by 2030)

Computing resource allocation
management unit

Server level

Computing device level

Computing device level

Energy efficiency

Measurements made.
Independent of workload, event,and traffic

Closely aligned with accurately
measured and controlled
workload, event, and traffic

We aim for significant reduction
compared to Phase 2.

Data transfer

Supported by host board

Direct connection between XPUs
(GPU, DPU)

Direct connection between XPUs
(GPU, DPU)

Cache coherence memory space

COTS scale

Rack scale (via CXL)Rack scale (via CXL)RDMAApplication within datacenter

Application across datacenters(by RDMA over APN)

Application across datacenters(by RDMA over APN)

Logical server configuration

Server level

Module card level (PCIe card,
CXL card, etc.)

Chip level

Security

Current cipher (e.g., RSA, DH)

Post-quantum cryptography

In addition to post-quantum
cryptography, its management
using zero-trust concept

Computing resource
configuration time

Several hours

Several minutes

Several seconds

Applications that require very
tight time constraints anddeterministic processing times

Unfeasible

Processing time can be
guaranteed deterministically at
the millisecond level.

Processing time can be
guaranteed deterministically at
the millisecond level.

Storage/data transfer

Transfer at local level

Transfer at regional level

Transfer at national level

COTS: commercial off-the-shelf
DH: Diffie–Hellman key exchange
RDMA: remote direct memory access
RSA: Rivest–Shamir–Adleman

The time needed for computing resource configuration is currently in hours, but the use of LSNs will
reduce the configuration time to minutes in Phase 2
and seconds in Phase 3 (Table 1).

released by the IOWN Global Forum.
References[1]

7. Conclusions and summary
This article presented an overview of the DCI functional architecture.
For IOWN to enable advanced information technology to unleash its full potential in a data-driven
society, a new ICT infrastructure that integrates thecomputing and networking infrastructures is required
under the condition that a high-speed network withmanaged quality of service is available. IOWN’s DCI
serves as this new ICT infrastructure.
Due to limited space, this article does not describe
some of the important concepts that support the DCI,
such as infrastructure orchestrator, function-dedicated network, and resource pool. For these concepts,
refer to the DCI Functional Architecture version 2.0

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Vol. 22 No. 2 Feb. 2024

[2]

[3]

[4]

[5]

R. Kurebayashi, T. Ishizaki, S. Priyankara, C. Schumacher, and S.
Mizuno, “Data-centric Infrastructure for Supporting Data Processingin the IOWN Era and Its Proof of Concept,” NTT Technical Review,Vol. 22, No. 1, pp. 64–72, Jan. 2024. https://doi.org/10.53829/
ntr202401fa8
IOWN Global Forum, “Data-Centric Infrastructure Functional Architecture,” Ver. 2.0, Mar. 2023. https://iowngf.org/wp-content/
uploads/2023/04/IOWN-GF-RD-DCI_Functional_Architecture2.0.pdf
Y. Kainuma, T. Takeda, J. Kani, and H. Nishizawa, “Activities for
Detailing the Architecture of the Open APN and Promoting Its Practical Application,” NTT Technical Review, Vol. 22, No. 2, pp. 19–25,
F e b . 2 0 2 4 . h t t p s : / / n t t - r e v i e w. j p / a r c h i v e / n t t t e c h n i c a l .
php?contents=ntr202402fa2.html
IOWN Global Forum, “Reference Implementation Model (RIM) for
the Area Management Security Use Case,” Ver. 1, p. 64, Figure B.2-2:
An Example of Data Pipeline Diagram (Big Mail System), Jan. 2022.
https://iowngf.org/wp-content/uploads/formidable/21/IOWN-GFRD-RIM-for-AM-Use-Case-1.0.pdf
IOWN Global Forum, “IOWN Global Forum: Key Values and Technology Evolution Roadmap,”
https://iowngf.org/wp-content/uploads/formidable/21/IOWN-GFRD-KVaTE_Roadmap-1.0-1.pdf

46

Feature Articles

Hiroshi Yoshida

Senior Manager, IOWN Development Office,Research and Development Planning Department, Research and Development Market Strategy Division, NTT Corporation.
He received a Ph.D. from the Department of
Human and Engineered Environmental Studies,
the University of Tokyo, in 2011. Since joining
NTT, he has been engaged in operational
research, including network operation systems
development and basic research on optimal staffing and safe work environments. He is currently
in charge of arranging PoCs with other IOWN
Global Forum member companies.

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Vol. 22 No. 2 Feb. 2024

47

Global Standardization Activities

Standardization Trends in IEEE
802.11be/bn
Akira Kishida
Abstract

We introduce the latest trends in the Institute of Electrical and Electronics Engineers (IEEE) 802.11be(11be), which will be the main standard of the next generation of wireless local area networks (LANs),
and the IEEE 802.11bn (11bn), the following primary standard of 11be. The IEEE 802.11 standard is themost used unlicensed wireless LAN system globally, recognized as Wi-Fi. Wi-Fi is implemented inlaptop computers and smartphones, Internet of Things devices, and home appliances. Its usage models
also extend from consumer markets to business solutions such as industrial automation and intelligent
agriculture in the 11bn era.
Keywords: IEEE 802.11bn, IEEE 802.11be, Wi-Fi 7

1. Standardization of IEEE 802.11 WG
The Institute of Electrical and Electronics Engineers (IEEE) 802.11 Working Group (WG) [1] is agroup that discusses and decides the technical specifications of the IEEE 802.11 wireless local area network (LAN) systems, recognized as Wi-Fi*. The WG
is a subsidiary of the IEEE Standards Association(SA) that covers standardization activities of IEEE.
The IEEE 802.11 WG consists of several subgroups,
such as Task Groups (TGs), which create technicalspecifications, and Study Groups (SGs), which clarify the scope and target of TGs. Other subgroup types
are Interest Topic Groups (TIGs), which discuss thepossibility of standardization for specific topics,
Standing Committees (SCs), which discuss general
topics of wireless LAN systems, and Ad-hoc groups(AHGs) that address global issues. The technicalspecification defined by TGs is to be released as theIEEE 802.11xx. Usually, “xx” is a combination ofalphabet. Hereafter, we assume that 11xx indicates
the technical specification of the IEEE 802.11xx.
Table 1 lists each subgroup of the IEEE 802.11 WG
and its topic as of December 2023.

2. Certification of wireless LAN devices by
Wi-Fi Alliance
Wi-Fi Alliance [2] is an industrial organization thatcertifies the interoperability of devices and promotes
marketing for wireless LAN systems and devices.
Wi-Fi Alliance gives certification of a wireless LAN
device on the basis of the IEEE 802.11 standard as
Wi-Fi X, which passed the inspection of the test planon the basis of the corresponding IEEE 802.11 standard. Here, X denotes the corresponding Wi-Fi generation number. For example, a wireless LAN device
with Wi-Fi 6/6E certification means that the device
has passed the Wi-Fi test plan of the 11ax. A test planfor Wi-Fi 7 is currently being discussed on the basisof the 11be draft standard.
3. IEEE 802.11be: Extremely High Throughput
TGbe is discussing and defining the 11be standard
as the main technical specification next to 11ax. The
project name of creating 11be is Extremely HighThroughput (EHT), and the aims are enabling at least
one mode of operation capable of supporting a maximum throughput of at least 30 Gbit/s at the media*

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Wi-Fi is a registered trademark of Wi-Fi Alliance.

48

Global Standardization Activities

Table 1. Subgroups of the IEEE 802.11 WG.
Subgroup

Project topic

Completion date

TGbb

Light Communications

June 2023

TGbe

Extremely High Throughput

December 2024

TGbf

Wireless LAN Sensing

March 2025

TGbh

Randomized and Changing MAC Addresses

September 2024

TGbi

Enhanced Data Privacy

March 2026

TGbk

320 MHz Positioning

November 2024

TGme

802.11 Accumulated Maintenance Changes

September 2024

TGbn

Ultra High Reliability

May 2028

AMP SG

Ambient Power-

AIML TIG

Artificial Intelligence / Machine Learning-

ARC SC

Architecture-

COEX SC Coexistence-

JTC1 SC

Support Liaison with Joint Technical Committee1 / SC6-

WNG SC

Wireless LAN Next Generation-

ITU AHG

International Telecommunication Union Liaison-

access control (MAC) layer level and defining at least
one mode of operation capable of improved worstcase latency and jitter. As well as 11ax, 11be will use
the frequency band of 6 GHz in addition to those of
2.4 and 5 GHz. In Japan, a part of the 6 GHz band
(5925–6425 MHz) was made available from September 2, 2022.
TGbe was established in May 2019 and will end
their standardization activities in December 2024.
Draft standard 5.0 was released in December 2023,
and almost all specifications of various features aresettled. Detailed functions are under review per comments from IEEE 802.11 WG members. The editorial
review called Mandatory Draft Review (MDR),
which is required to issue the formal IEEE standard,has begun. A ratification vote called Sponsor Ballot(SB) at the IEEE SA level will begin in January 2024.
Thus, the status of the standardization process of
11be is in the final phase to be published.
3.1 Main technical features of IEEE 802.11be
New features for improving frequency-utilization
efficiency, wider frequency bandwidth, and latency
reduction will be defined in the 11be. Multi-link
operation is a new feature that was never defined in
the old standard before 11ax. Combining these features enables a 2.4 times improvement of the maximum data rate at the physical (PHY) layer from 9.6
Gbit/s (11ax) to 23 Gbit/s (11be). Applying the multilink operation that enables simultaneous transmissions will enhance throughput at the MAC layer, and
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11be aims to achieve a maximum throughput of atleast 30 Gbit/s by using this feature. Table 2 lists theeffect of throughput enhancement of 11be comparedwith 11ax.
(1)	Features of frequency-utilization efficiency andwider frequency bandwidth
The 11be standard defines 4096 quadrature amplitude modulation (QAM) as a modulation scheme ofeach subcarrier of the orthogonal frequency divisionmultiplexing (OFDM) symbol, which achieves a 1.2
times higher modulation rate than 11ax (1024 QAM).
In 11ax, a resource unit (RU) that indicates grouped
subcarriers in a channel bandwidth of orthogonalfrequency division multiple access (OFDMA), is
assigned to each station (STA). Multiple RU (MRU)
defined in 11be, however, enables the assignment ofmultiple RUs to an STA. This feature establishes several patterns of RU combinations, allowing for more
flexible resource allocation.
(2) Multi-link operation
The 11be standard specified a new feature defined
as multi-link operation that was never defined in theold standard before 11ax. In multi-link operation, awireless device defined as a multi-link device (MLD)
can support more than one affiliated STA or accesspoint (AP) and operate using one or more affiliated
STAs or APs. This feature enables an AP/STA tobundle multiple transmission paths (links), thusachieves a higher transmission rate in accordancewith the number of links. Figure 1 shows a conceptual image of multi-link operation.
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Global Standardization Activities

Table 2. Effect of throughput enhancement of 11be.

PHY
layer

MAC
layer

Functions

IEEE 802.11ax

IEEE 802.11beEnhancementfrom 11ax

Maximum modulation
level

1024 QAM(10 bit/subcarrier)4096 QAM(12 bit/subcarrier)

1.2 times

Maximum channel
bandwidth

160 MHz

320 MHz

2 times

Maximum number ofspatial stream

8

8

Same

Maximum data rate

9.6 Gbit/s

23 Gbit/s(without multi-link
operation)

2.4 times

Multi-link operation

None

Maximum 15 links

In accordancewith the numberof links

AP MLD 1
AP1

AP2

AP3

AP1
AP2
Link 1 Link 2 Link 3
STA3

STA1
STA2

STA1

STA2

STA3

Non-AP MLD 1

Link 4 Link 5 Link 6
STA4

STA5

STA6

Non-AP MLD 2

Transmission paths formed by AP and STA
are independent.

Multiple affiliated APs or STAs in a single MLD coordinate
mutually and execute simultaneous transmissions.

(a) Conventional wireless LAN’s operation(b) Multi-link operation in 11beFig. 1. Concept of multi-link operation.

(3) Feature of latency reduction
In 11be, the latency-reduction feature defined as
restricted target wake time (TWT) will be supported.
This feature ensures a specific period within thescheduled service period (SP) for latency-sensitive
traffic. Therefore, contention between latency-sensitive traffic and non-latency sensitive traffic is
reduced, and latency-sensitive traffic generated periodically can be transmitted more reliably.
(4) Other new features
A new peer-to-peer (P2P) feature without setting up
any connections between STAs will be defined. In
this new P2P feature, called triggered transmission
opportunity (TXOP) sharing mode 2, an AP obtains
time for P2P transmission representatively, and thedesignated STA can transmit data frames to the other
STA directly. Emergency preparedness communicaNTT Technical Review

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tions service (EPCS) will also be defined in 11be.
This feature can prioritize the transmission of specific STAs authorized by networks in advance.
3.2 Standardization activities of NTT for 11be
The predecessors of TGbe were EHT TIG and EHT
SG, which were launched in 2018 ( TGbe was formed
in 2019). The focus was initially only on improving
maximum throughput, and reducing latency was notincluded in the scope of 11be. In the subgroup called
Real Time Application (RTA) TIG, NTT and several
companies discussed and considered latency and jitter reduction for industrial automation, cloud gaming,and so on around the same time as EHT TIG and SG.
NTT collaborated with the RTA TIG’s leading contributors to create a report document [3] that summarizes RTA TIG’s activities. We input this document
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Global Standardization Activities

into EHT SG and emphasized the importance oflatency-reduction features when EHT SG created the
Project Authorization Request (PAR), which defines
the scope and necessity of the standard, and Criteria
for Standards Development (CSD), which describes
the significance of the standard and market requirements. This document is referenced not only in 11bebut also in the PAR and CSD of 11bn. After the establishment of TGbe, NTT continued to solicit that 11beshould have some form of latency reduction andnotification of latency related information features.
Therefore, 11bn will have a latency-reduction feature, such as restricted TWT, and new signaling information, such as quality-of-service characteristic elements.
4. IEEE 802.11bn: Ultra High Reliability
In parallel with the standardization discussions for
11be, discussions were underway to formulate thenext primary standard after 11be. In January 2022,
the establishment of a new primary SG following
11be was proposed at the Wireless Next Generation(WNG) SC, which discusses the need for standardization regarding specific functions and topics. Afterseveral months of discussion, the Ultra High Reliability (UHR) SG was established and launched in
September 2022. The main topic of UHR SG was tocreate the PAR and CSD for the next generation of
wireless LANs following 11be. On the basis of theagreement of creating the PAR and CSD, TGbn wasestablished in November 2023. The standardizationof 11bn is scheduled to be completed in May 2028.
Though the main scope of the existing primary standards, 11bn or before, is the enhancement of maximum throughput or improving channel efficiency,
11bn focuses on improving the reliability of wirelessLANs. Specifically, in the same frequency band as
11be (2.4/5/6-GHz band), latency characteristics,
packet loss, and throughput characteristics inreceived power according to distance will be
improved by 25% compared with 11be in 11bn.
Improved AP power saving and P2P will also be considered. As of December 2023, UHR SG mainly discusses functional proposals from various companies
to achieve the scope described in the PAR and CSD.
4.1 Features under consideration for 11bn
In UHR SG and TGbn, many companies have proposed various features for 11bn as follows. Note thatthese features have not been decided for technicalspecifications but are under discussion.
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(1) Multi-AP coordination
Multi-link operation defined in 11be enables coordination using multiple wireless interfaces equippedwith a single MLD. In contrast, multi-AP coordination improves frequency efficiency and reliability
through cooperation between multiple independentAPs. This feature had been discussed in early TGbe;however, TGbe decided not to include this feature in
11be specifications due to the timeline complianceand implementation complexity. Therefore, discussions of multi-AP coordination have been taken over
by TGbn. Several types of coordination forms areunder consideration. Coordinated spatial reuse (Co-SR)
controls transmission power to decrease interference
to STAs. Coordinated beamforming (Co-BF) enables
simultaneous transmission to each target STA of each
AP without generating interference by coordinatedbeamforming and nulling. In joint transmission (JT),multiple APs transmit identical signals simultaneously with synchronization, and a receiver STA can
combine multiple identical signals. Figure 2 showsconceptual images of multi-AP coordination.
(2) Distributed RU
As described in the previous section, the MRU feature was defined in 11be. TGbn is discussing its
enhancement to distributed-tone RUs (dRUs). Thisfeature does not assign RUs by several patterns ofcombinations but freely, which offers more flexibility. For example, the same data block can be assigned
to multiple RUs for redundancy, and the reliability ofdata transmission improves.
(3) Latency reduction
Restricted TWT defined in 11be can protect a specific period for latency-sensitive traffic generated
periodically. In addition to the enhancement of
restricted TWT, support for non-periodic (sporadic)
latency-sensitive traffic is under consideration in
11bn. Preemption can interrupt latency-sensitive traffic into ongoing transmission by the frequency and/ortime domain and transmit with priority. A functionthat ensures transmission of latency-sensitive traffic
by using triggered TXOP sharing and enhancementof a buffer status report, which notifies an AP or an
STA of the requirement of latency bound in real time,
are also considered.
(4) Other features under consideration
Power-saving functions applying multi-link operation and/or multi-AP coordination, extension of area
coverage of a wireless LAN network using relay
architecture, and enhancement of security functions
are under discussion in 11bn.

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Global Standardization Activities

APs control transmission power
mutually and decrease interference
to corresponding STAs.

AP1

STA1

Simultaneous transmission to each target STA ofeach AP without generating interference isachieved by coordinated beamforming and nulling.

AP1

AP2

STA2

AP2

STA1

(a) Coordinated Spatial Reuse

Multiple APs transmit identical signals
simultaneously, and a receiver STA can
combine multiple identical signals.

AP1

STA2

AP2

STA1

(b) Coordinated Beamforming(c) Joint Transmission

Fig. 2. Conceptual images of multi-AP coordination.

4.2 Discussion on utilizing millimeter wave
Whether to include the millimeter-wave frequency
band (60 GHz) as the target frequency in addition toexisting frequency bands such as 2.4/5/6 GHz was animportant topic in UHR SG, which discusses thescope of 11bn. Although 11ad/ay are standards for
wireless LAN systems that use millimeter waves, this
discussion topic in UHR SG assumes using millimeter waves as additional links for multi-link operation
features, which is unrelated to 11ad/11ay. As a resultof the discussion, UHR SG decided that the millimeter-wave band should be discussed in a separate subgroup from TGbn, and the Integrated Millimeter
Wave (IMMV) SG was launched in November 2023.

to including important business use cases such asindustrial automation, robotics, logistics, and smart
agriculture in these prospective documents for establishing TGbn [6]. At the same time as the TGbn foundation, Yusuke Asai, a distinguished researcher ofNTT, was elected 11bn leadership officer (Secretary).

4.3 Standardization activities of NTT for 11bn
NTT has continued to promote the need to improvelatency characteristics and reliability in wireless
LAN since RTA TIG launched in 2018 and proposes
to expand the Wi-Fi market not only for the consumer but also for business use cases requiring certain communication qualities such as low latency.
This contribution changed the scope of mainstream
wireless LAN standards from improving maximum
throughput, such as 11be or before, to improving reliability in 11bn. NTT also proposed the PAR [4] andCSD [5] of 11bn with other companies and contributed

References

NTT Technical Review

Vol. 22 No. 2 Feb. 2024

5. Conclusions
This article explained the standardization trends inand NTT’s activities for the next generation of
extremely high throughput wireless LAN IEEE
802.11be and the next leading standard after 11be, theultra-high reliability wireless LAN IEEE 802.11bn.

[1]
[2]
[3]
[4]
[5]
[6]

IEEE 802.11 Working Group, https://www.ieee802.org/11/
Wi-Fi Alliance, https://www.wi-fi.org/
K. Meng, A. Jones, D. Cavalcanti, K. Iyer, C. Ji, K. Sakoda, A.
Kishida, F. Hsu, J. Yee, L. Li, and E. Khorov, “IEEE 802.11 Real Time
Applications TIG Report,” IEEE 802.11-19/2009r6, Mar. 2019.
L. Cariou, V. Erceg, L. Hervieu, C. Hu, B. Hart, A. Andersdotter, andA. Kishida, “802.11 UHR Proposed PAR,” IEEE 802.11-23/0078r7,
Mar. 2023.
L. Cariou, L. Hervieu, C. Hu, B. Hart, and A. Kishida, “IEEE 802.11
UHR Proposed CSD,” IEEE 802.11-23/0079r10, Mar. 2023.
A. Kishida, Y. Asai, K. Nagata, R. Nagatsu, and Y. Takatori, “Use
Cases for Wi-Fi Business Solutions in UHR,” IEEE 802.1122/1493r0, Sept. 2022.

52

Global Standardization Activities

Akira Kishida

Senior Research Engineer, NTT Access Network Service Systems Laboratories.
He received a B.E. and M.E. from Tokyo University of Agriculture and Technology in 2005
and 2007 and Ph.D. in engineering from the
University of Tsukuba, Ibaraki, in 2015. In 2007,
he joined NTT Access Network Service Systems
Laboratories then joined NTT DOCOMO in
2015. He is currently engaged in the standardization of the IEEE 802.11be and IEEE 802.11bn as
the delegate of NTT Access Network Service
Systems Laboratories. He received the IEICE(Institute of Electronics, Information and Communication Engineers) Young Researcher’sAward in 2010.

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53

Practical Field Information about
Telecommunication Technologies
Practical Field Information about Telecommunication Technologies

Optical Loss Prediction Tool 1.0
toward Enabling Preventive
Maintenance of Optical Fiber Cables
Technical Assistance and Support Center, NTT EAST
Abstract

Technical Assistance and Support Center, NTT EAST developed the Optical Loss Prediction Tool 1.0
for predicting transmission loss of optical fibers. This article presents an overview and the functions of
this tool. This is the eightieth article in a series on telecommunication technologies.
Keywords: OTDR, transmission loss, loss prediction

1. Introduction
Optical fiber cables are deployed in diverse environments, such as urban and mountainous areas, andplay a role of a social infrastructure supporting notjust information and communication services but also
various social activities. Transmission loss of opticalfibers in the cable may increase due to age-related
deterioration caused by the environmental conditions
under which the cable is deployed. To maintain communication quality through optical fiber cables as asocial infrastructure, it is important to regularly
monitor transmission loss of the optical fibers andpreventively take necessary maintenance, such as
cable replacement, before a problem occurs.
Technical Assistance and Support Center (TASC),NTT EAST developed the Optical Loss Prediction
Tool 1.0 for predicting the transmission loss of optical fibers from periodically conducted and stored
optical measurement data. This article presents an
overview and the functions of this tool.
2. Development background
Optical fiber cables may deteriorate over time dueto the environmental conditions, which can cause an
NTT Technical Review

Vol. 22 No. 2 Feb. 2024

increase in transmission loss [1]. For example, inunderground optical fiber cables that have been laid
in a humid environment for an extended period, blisters may form inside the coating of the optical fibers,
as shown in Fig. 1. In such optical fibers, the continuous application of multiple invisibly small bending(microbending) causes excessive transmission loss.
Even small locally, the transmission loss accumulated over long distance (over hundreds of meters toseveral kilometers) can increase so much that service
cannot be provided, when microbending occurs. To
maintain optical fiber cables in good condition, it isimportant to periodically conduct tests to determine
the state of transmission loss and take preventive
measures, such as replacing cables, before a problem
occurs.
An optical time domain reflectometry (OTDR) is
generally used to determine the condition of opticalfiber cables. An OTDR uses pulsed light as a test light
injected into an optical fiber and measures the backscattered light and reflected light. The round-trip
delay of the backscattered or reflected light is proportional to the distance to the scattering or reflection pointin the optical fiber; therefore, the transmission statealong the length of the optical fiber cable can be estimated by acquiring the intensity of the backscattered54

Practical Field Information about Telecommunication Technologies

Blisters inside the coating of optical fiber

Backscattered
light intensity

Fig. 1. Magnified image of an optical fiber with microbending.

Abnormal slope

Distance

Fig. 2. Waveform of optical fiber cable with increasing transmission loss measured using an OTDR.

or reflected light as a function of time [2]. Figure 2
shows that in a cable section where transmission loss
has increased due to cable aging, etc., the slope of the
waveform measured with an OTDR, which is thebackscattered light intensity change with respect todistance, increases abnormally. Therefore, by analyzing the slope of the waveform with respect to distance, it is possible to determine the condition oftransmission loss.
NTT EAST Group conducts monthly optical measurements on optical fiber cables in optical accessnetworks using an OTDR. However, these periodic
OTDR measurements only confirm the presence orabsence of abnormalities at the time of measurement,
and there is no method for detecting abnormalities
before they become apparent. If an abnormality isdetected during periodic OTDR measurements andthe abnormal optical fiber cable must be renewed, it
can take several months to a year from design tocompletion of installation. Therefore, it might be difficult to secure assignable fibers if the abnormality isaddressed after it becomes apparent.
Responding to the above issues, TASC developed
the Optical Loss Prediction Tool 1.0 to identify transmission loss abnormalities in advance. This tool uses
NTT Technical Review

Vol. 22 No. 2 Feb. 2024

periodically conducted and stored optical measurement data to analyze time-series changes in pasttransmission loss and enables prediction of futuretransmission loss.
3. Overview of Optical Loss Prediction Tool 1.0
Figure 3 shows an overview of the Optical Loss
Prediction Tool 1.0. The tool has two main functions:(1) time-series analysis of transmission loss and (2)prediction of future transmission loss. The following
sections explain each function.
3.1 Time-series analysis of transmission loss
The tool’s first function is to visualize time-serieschanges in transmission loss in any cable section. To
use this function, the folder containing optical periodic measurement data is specified on the input
screen. The tool then loads all optical periodic measurement data from the specified folder at once. The
loaded measurement data, which is compliant with
the Standard OTDR Record (SOR) data format [3],includes the backscattered light intensity and distanceinformation measured using an OTDR, as well as themeasurement date. When analyzing transmission
55

Practical Field Information about Telecommunication Technologies

Distance

Distance

March OTDR
measurement data
Increased loss due
to cable aging, etc.

Backscattered
light intensity

February OTDR
measurement data
Backscattered
light intensity

Backscattered
light intensity

January OTDR
measurement data

Distance

Optical periodic measurements data (SOR file-extension format)

Optical Loss Prediction Tool 1.0

Transmission loss

Function (1): Time-series analysisof transmission loss

Function (2): Prediction of futuretransmission loss
Predicted
Prediction
Date
loss
error

Measurement dateFig. 3. Overview of Optical Loss Prediction Tool 1.0.

ate

td

re

su

a
Me

n
me

April
Loss

Backscattered light intensity

Tool screen

MarchMeasuredvalue
Predicted
value

February

January
Specified section

Distance

Date

Fig. 4. Schematic diagram of time-series analysis of transmission loss.

loss, the distance information for the cable section is
specified. The transmission loss values are then automatically analyzed for all loaded SOR extension databy calculating the backscattered-light-intensitychanges in the cable section on the basis of the specified distance information. These values are associated with the date of measurement recorded in each
SOR extension data, and displayed in a grapharranged in order of measurement date, as shown in
NTT Technical Review

Vol. 22 No. 2 Feb. 2024

Fig. 4. This graphical visualization of time-serieschanges in transmission loss enables us to see thedegradation trend of transmission loss in the specified section.
3.2 Prediction of future transmission loss
The tool’s second function is to predict future transmission loss in the specified cable section. This function uses the analyzed time-series data mentioned in56

Practical Field Information about Telecommunication Technologies

Measurement datePredicted loss (dB/km)

Prediction error (dB/km)

Fig. 5. Example results of output by transmission loss prediction.

Section 3.1 as training data for transmission loss
prediction. Transmission loss prediction is carried out
by applying a regression analysis to the time-series
data and extrapolating the obtained regression line tothe specified prediction date, as shown with the redline in Fig. 4. The predicted losses are listed next tothe specified prediction date, as shown in Fig. 5, in amanner that makes it possible to quantitatively understand the predicted increase in transmission loss. As
also shown in Fig. 5, the predicted values of transmission losses as well as estimated prediction errors are
displayed as a list up to the specified prediction
month, enabling a quantitative understanding oftransmission loss deterioration prediction. The prediction errors, which are automatically estimated on
the basis of the specified confidence coefficient(probability that the prediction value will fall within
the error range) and prediction date, are displayed
together with the prediction values in this list box.
This function makes it possible to determine the prediction value of future transmission loss and error
range, which can be useful in planning cable renewals.
4. Conclusion
This article introduced a tool for predicting futuretransmission loss in optical fiber cables. We believe

NTT Technical Review

Vol. 22 No. 2 Feb. 2024

that this tool will help prevent failures caused bychanges in transmission loss due to age-related deterioration, etc., and contribute to the planned renewalof cables. Toward practical use for cable maintenance, we are currently discussing the utilization
method of this tool with the relevant departments of
NTT EAST and NTT WEST. We will also improve
our prediction accuracy by incorporating machinelearning and other methods into this tool.
The Access Network Engineering Group in TASC
offers technical support to resolve challenging accessfacility failures that occur in the field throughout
Japan. We will continue to contribute to field troubleshooting and develop tools that enhance technicalskills and efficiency in the field by leveraging theexpertise acquired from technical support and theknowledge gained through the investigation of thecauses of failures.
References
[1]

[2]
[3]

K. Sohma, N. Iwaguchi, T. Kawano, T. Fujii, and Y. Koyano, “Estimation of Long-term Change in Physical Property of Optical Fiber Coating Considering Effect of Humidity,” SEI Technical Review, Vol. 187,
pp. 12–17, 2015.
NTT EAST, “Methods for Finding Failures in Optical Fibers,” NTT
Technical Journal, Vol. 18, No. 10, pp. 53–54, 2006 (in Japanese).
Telcordia SR-4731, “Optical Time Domain Reflectometer (OTDR)
Data Format,” Issue 2, 2011.

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External Awards
Technical Development Award
Winners: Tatsuya Kako, NTT Computer and Data Science Laboratories; Hironobu Chiba, NTT Computer and Data Science Laboratories
Date: May 27, 2023
Organization: Acoustical Society of JapanFor development of open-ear earphones that minimize sound leakage by radiating antiphase sound waves.
SCIS Innovation Paper Award
Winners: Junko Takahashi, NTT Social Informatics Laboratories;
Shota Kita, NTT Basic Research Laboratories; Akihiko Shinya, NTT
Basic Research Laboratories; Kazumaro Aoki, Bunkyo University;
Koji Chida, Gunma University; Fumitaka Hoshino, University ofNagasaki
Date: July 20, 2023
Organization: The Institute of Electronics, Information and Communication Engineers (IEICE) Technical Committee on Information
Security (ISEC)For “Fast Graph Fourier Transform based Graph Signal Denoising.”
Kekicheff Award
Winner: Eikazu Niwano, NTT Social Informatics Laboratories
Date: November 10, 2023
Organization: GlobalPlatform
For his outstanding dedication and commitment to GlobalPlatform. He has been a key part of its organization since 2005, servingon the GlobalPlatform Board of Directors and leading the Japan Task
Force. This award recognizes his extraordinary, impactful efforts.
MNC 2022 Most Impressive Presentation Award
Winners: Katsuhiko Nishiguchi, NTT Basic Research Laboratories;
Akira Fujiwara, NTT Basic Research Laboratories; Kensaku Chida,
NTT Basic Research Laboratories
Date: November 14, 2023
Organization: 35th International Microprocesses and Nanotechnology Conference (MNC 2022)

For “Photonic Cryptographic Circuit Technology and Operation
Verification.”
Published as: J. Takahashi, S. Kita, A. Shinya, K. Aoki, K. Chida,
and F. Hoshino, “Photonic Cryptographic Circuit Technology andOperation Verification,” Proc. of the 40th Symposium on Cryptography and Information Security (SCIS 2023), 1E2-2, Kitakyushu,
Fukuoka, Japan, Jan. 2023.

For “Room-temperature Single-electron Sensor for AC Signals
beyond an RC Time Constant ~ Energy Transfer via a Non-leakage
DRAM in Non-equilibrium ~.”Published as: K. Nishiguchi, A. Fujiwara, and K. Chida, “Roomtemperature Single-electron Sensor for AC Signals beyond an RC
Time Constant ~ Energy Transfer via a Non-leakage DRAM in Nonequilibrium ~,” MNC 2022, 10B-2-1, Tokushima, Japan, Aug. 2023.

Young Scientist Award
Winner: Hiroyuki Fukumoto, NTT Network Innovation Laboratories
Date: August 21, 2023
Organization: 35th Union Radio-Scientifique Internationale General Assembly and Scientific Symposium (URSI GASS 2023)

MNC 2022 Most Impressive Poster
Winners: Megumi Kurosu, NTT Basic Research Laboratories; Daiki
Hatanaka, NTT Basic Research Laboratories; Ryuichi Ohta, NTT
Basic Research Laboratories; Keiko Takase, NTT Basic ResearchLaboratories; Hiroshi Yamaguchi, NTT Basic Research Laboratories;
Yoshitaka Taniyasu, NTT Basic Research Laboratories; Hajime
Okamoto, NTT Basic Research Laboratories
Date: November 14, 2023
Organization: MNC 2022

For “Implementation of Bidirectional High-rate Underwater
Acoustic Communication Systems for Fully Wireless-controlled
Remotely Operated Vehicles.”Published as: H. Fukumoto, R. Okumura, Y. Fujino, S. Ohmori, Y.
Ito, T. Ishihara, and Y. Tabata, “Implementation of Bidirectional
High-rate Underwater Acoustic Communication Systems for Fully
Wireless-controlled Remotely Operated Vehicles,” URSI GASS
2023, Sapporo, Hokkaido, Japan, Aug. 2023.
Engineering Sciences Society Service Award
Winner: Yukihiro Bandoh, NTT Computer and Data Science Laboratories
Date: September 13, 2023
Organization: IEICE
For contribution to the management and activities of the TechnicalCommittee on Smart Info-Media Systems.
Signal Processing Young Researcher’s Award
Winner: Takayuki Sasaki, NTT Computer and Data Science Laboratories
Date: November 7, 2023
Organization: IEICE Technical Group on Signal Processing

NTT Technical Review

Vol. 22 No. 2 Feb. 2024

For “High-overtone Bulk Acoustic Resonator with Epitaxial AlN
Layer Grown on n-SiC.”
Published as: M. Kurosu, D. Hatanaka, R. Ohta, K. Takase, H.
Yamaguchi, Y. Taniyasu, and H. Okamoto, “High-overtone Bulk
Acoustic Resonator with Epitaxial AlN Layer Grown on n-SiC,”
MNC 2022, 11P-4-31, Tokushima, Japan, Aug. 2023.
Best Paper Award
Winner: Shin’ya Yamaguchi, NTT Computer and Data Science
Laboratories
Date: November 15, 2023
Organization: The 15th Asian Conference on Machine Learning(ACML 2023)
For “Generative Semi-supervised Learning with Meta-Optimized
Synthetic Samples.”Published as: S. Yamaguchi, “Generative Semi-supervised Learningwith Meta-Optimized Synthetic Samples,” Proc. of ACML 2023,
Istanbul, Turkey, Nov. 2023.

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Runner-up rank
Winners: Takumi Fukami, NTT Social Informatics Laboratories;
Yuusuke Yamasaki, NTT Social Informatics Laboratories; Iifan
Tyou, NTT Social Informatics Laboratories; Kenta Niwa, NTT Communication Science Laboratories
Date: November 15, 2023
Organization: NeurIPS 2023 competition on “Privacy Preserving
Federated Learning Document VQA” (PFL-DocVQA)
For “Differential Privacy Analysis for DP-CLGECL.”IDSA Ambassador
Winner: Koki Mitani, NTT Social Informatics Laboratories
Date: November 22, 2023
Organization: International Data Spaces Association (IDSA)For outstanding commitment to promoting international development and cooperation of data spaces driven by IDSA.
Best Paper Award
Winners: Atsushi Taniguchi, NTT Network Innovation Laboratories; Yasuhiro Mochida, NTT Network Innovation Laboratories;
Sakae Chikara, NTT Social Informatics Laboratories; Yasuyuki
Sanari, NTT Network Innovation Laboratories; Keizo Murakami,
NTT Social Informatics Laboratories; Momoko Miura, NTT Network Innovation Laboratories; Hirokazu Takahashi, NTT Network
Innovation Laboratories; Koichi Takasugi, NTT Network Innovation
Laboratories; Hiroki Itoh, NTT Social Informatics Laboratories;
Daigoro Yokozeki, NTT Social Informatics Laboratories
Date: November 30, 2023
Organization: International Conference on Emerging Technologies
for Communications (ICETC) 2023
For “Disaggregation Architecture of Quantum-safe Security for
Optical & Packet Transport Equipment.”
Published as: A. Taniguchi, Y. Mochida, S. Chikara, Y. Sanari, K.
Murakami, M. Miura, H. Takahashi, K. Takasugi, H. Itoh, and D.
Yokozeki, “Disaggregation Architecture of Quantum-safe Security
for Optical & Packet Transport Equipment,” Proc. of ICETC 2023,
Sapporo, Hokkaido, Japan, Nov./Dec. 2023.
IEEE MTT-S Japan Chapter Young Engineer Award
Winner: Masahito Nakamura, NTT Device Technology Laboratories
Date: November 30, 2023
Organization: IEEE Microwave Theorty and Technology Society(MTT-S) Japan Chapter
For “Broadband Dielectric Spectroscopy for Quantitative Analysis
of Glucose and Albumin in Multicomponent Aqueous Solution.”
Published as: M. Nakamura, T. Tajima, and M. Seyama, “Broadband

NTT Technical Review

Vol. 22 No. 2 Feb. 2024

Dielectric Spectroscopy for Quantitative Analysis of Glucose andAlbumin in Multicomponent Aqueous Solution,” IEEE JERM, Vol.
6, No. 1, pp. 86–93, Mar. 2022.
IACR Asiacrypt Test-of-Time Award
Winners: Yu Sasaki, NTT Information Sharing Platform Laboratories (At the time of writing the paper); Kazumaro Aoki, NTT Information Sharing Platform Laboratories (At the time of writing thepaper)
Date: December 6, 2023
Organization: The International Association for Cryptologic
Research (IACR)
For “Preimage Attacks on 3, 4, and 5-Pass HAVAL.”
Published as: Y. Sasaki and K. Aoki, “Preimage Attacks on 3, 4, and5-Pass HAVAL,” ASIACRYPT 2008, LNCS, Vol. 5350, pp. 253–
271, 2008.
Globecom 2023 Best Paper Award
Winners: Katsuaki Higashimori, NTT Network Innovation Laboratories; Takafumi Tanaka, NTT Network Innovation Laboratories;
Takeru Inoue, NTT Network Innovation Laboratories
Date: December 7, 2023
Organization: IEEE Global Communications Conference (GLOBECOM) 2023
For “Efficient Routing Method for Reducing Significant Outages
in Optical Networks.”
Published as: K. Higashimori, T. Tanaka, and T. Inoue, “EfficientRouting Method for Reducing Significant Outages in Optical Networks,” GLOBECOM 2023, Kuala Lumpur, Malaysia, Dec. 2023.
IOP Trusted Reviewer status
Winner: Takuya Hatomura, NTT Basic Research Laboratories
Date: December 12, 2023
Organization: IOP Publishing2023 IEICE Communications Society OCS Young
Researchers Award
Winner: Akira Kawai, NTT Network Innovation Laboratories
Date: December 14, 2023
Organization: IEICE Technical Committee on Optical Communication Systems (OCS)
For “Precise Signal Demodulation in Dynamic Environments
Using Partially Frozen MIMO Adaptive Equalizers.”
Published as: A. Kawai, M. Nakamura, M. Takahashi, T. Kobayashi,
and Y. Miyamoto, “Precise Signal Demodulation in Dynamic Environments Using Partially Frozen MIMO Adaptive Equalizers,”
IEICE Tech. Rep., Vol. 122, No. 332, OCS2022-69, pp. 51–55, Jan.
2023.

59

Papers Published in Technical Journals andConference Proceedings
Northcott Numbers for the Weighted Weil Heights
M. Okazaki and K. Sano
Atti Accad. Naz. Lincei Rend. Lincei Mat. Appl., Vol. 34, No. 1,
pp. 127–144, July 2023.
We answer the question of Vidaux and Videla about the distribution of the Northcott numbers for the Weil height. We solve the same

NTT Technical Review

Vol. 22 No. 2 Feb. 2024

problem for the weighted Weil heights. These heights generalize boththe absolute and relative Weil height. Our results also refine those of
Pazuki, Technau, and Widmer.

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