NTT Technical Review
May 2015 Vol. 13 No. 5
Feature Articles: Movable and Deployable ICT Resource
Unit—Architecture for Quickly Responding to Unexpected
ICT Demand
Overview of Movable and Deployable ICT Resource Unit Architecture
Wireless Access Network System Using M2M Wireless Access for MDRU
High-speed and Plug-and-play Optical Interconnection for MDRUs
A Media Storage and Transmission System Using MDRUs
ICT Service for MDRUs
Overseas Deployment of MDRU: ITU Project in the Philippines, and
MDRU Standardization Efforts

Regular Articles
InP-based Membrane Optical Devices for Large-scale Photonic Integrated
Circuits

Global Standardization Activities
W3C TPAC 2014 Report and HTML5 Recommendation

New NTT Colleagues
We welcome our newcomers to the NTT Group

External Awards/Papers Published in Technical Journals
and Conference Proceedings
External Awards/Papers Published in Technical Journals and Conference
Proceedings

Feature Articles: Movable and Deployable ICT Resource Unit—
Architecture for Quickly Responding to Unexpected ICT Demand

Overview of Movable and Deployable
ICT Resource Unit Architecture
Toshikazu Sakano, Satoshi Kotabe, and Tetsuro Komukai
Abstract

When the Great East Japan Earthquake struck in 2011, a lot of the information and communication
technology (ICT) infrastructure suffered catastrophic damage, which triggered ICT service outages invarious areas for long periods of time. NTT Network Innovation Laboratories has been working to solve
this problem and has developed ICT architecture called the Movable and Deployable ICT Resource Unit
(MDRU). This architecture enables us to instantly deliver ICT services in damaged areas by installing atransportable ICT unit that accommodates the equipment necessary for providing ICT services. This
article presents an overview of the MDRU architecture and also introduces a research and development
project launched to realize it.
Keywords: resilient ICT, Wi-Fi, IP-PBX

1. Introduction
The Great East Japan Earthquake struck on March
11, 2011 and caused catastrophic damage over a wide
area of northeastern Japan due not only to the large
tremor but also to the devastating tsunami that it triggered. Telecommunication companies and information and communication technology (ICT) service*1
providers also suffered serious damage to their network infrastructure. Because of the damage, they had
to stop delivering ICT services in quite a few areas fora long time. At the same time, people in the damaged
areas urgently needed ICT services in order to confirm the safety of their loved ones such as family
members, relatives, friends, and neighbors, and tocollect information on what was happening and what
would happen next. This resulted in an explosion in
the demand for ICT services. This large supply-anddemand gap in the ICT sector strongly remindedpeople of the importance of the ICT infrastructure
and the necessity of service continuity even under
extreme disasters.
NTT Network Innovation Laboratories responded
to the public’s expectations by proposing the resilient
ICT architecture called the Movable and Deployable
ICT Resource Unit (MDRU)*2 [1]. The MDRU archi

tecture enables us to promptly reestablish ICT services in disaster-affected areas by installing transportable resource units that accommodate the functions necessary to deliver ICT services such as telephony and information sharing.
These Feature Articles report on the MDRU architecture and the research and development (R&D)
activities underway in NTT Network Innovation
Laboratories. This article gives an overview of the
MDRU architecture and explains the R&D projects
launched to realize it. Subsequent articles report the
major technologies used in the architecture, including
those for Wi-Fi-based network configuration [2],high-speed optical-link establishment [3], efficient
media storage and transmission [4], and convenient
ICT service delivery [5]. The last article reports on afeasibility study of MDRU use in an area in the Philippines, which was affected by Typhoon Haiyan in
2013, as an example of a specific activity being conducted toward MDRU commercialization [6].
*1	 ICT service: General term for a service related to the information
network and the Internet, which includes telephone and information services.
*2 MDRU: A transportable unit that accommodates equipment necessary to deliver ICT services. The word is also used for an ICT
architecture that uses the unit for instant delivery of ICT services.

NTT Technical Review

Feature Articles

Satellite communication

Wi-Fi
Wide area network

MDRU

Telecom building
Hub
Datacenters

Remaining optical fiber

Smartphone, personal computer

Local area network
Disaster area

Fig. 1. Concept of MDRU architecture.

2. MDRU architecture
The concept of the MDRU architecture is shown in
Fig. 1. An MDRU is a transportable unit accommodating the various resources necessary to deliver ICT
services. Once a disaster occurs, one or more MDRUs
are promptly transported to the disaster-affected areaand set up there. Each unit then rapidly forms a WiFi-based local area network (LAN) in its surroundingarea and starts delivering at least basic ICT services
to the people in the area. The MDRU is connected tothe existing wide area network (WAN) via remaining
optical fibers and/or satellite links. Once the MDRU
is connected to the WAN, it acts as a local information hub.
After the earthquake struck in 2011, NTT deployedtransportable systems such as switching systems,
base-station systems, and satellite public telephonesystems in an effort to respond to the disaster. The
objective of using these systems was to repair the
existing network infrastructure or to temporarily
replace damaged portions of the infrastructure.
Unfortunately, such systems took too long to install
and activate, as a lot of work was needed such as toconfirm the locations and degree of damage and to
make system adjustments. The repairs were patchwork, and services lagged. It sometimes took as longas a few weeks to recover basic service. Moreover, it
was not easy to flexibly respond to the unexpecteddemand that arose after the disaster such as when alarge evacuation center was established in an unpredictable place. The MDRU architecture, on the other
hand, is aimed at creating a new ICT service-delivery
environment anytime, anywhere irrespective of thesituation of the existing network infrastructure [7].
An MDRU forms a Wi-Fi-based LAN in its surroundVol. 13 No. 5 May 2015

ing area and promptly delivers basic ICT services
within the local area. The MDRU architecture enables
us to flexibly and instantly deliver ICT services in any
situation by optimizing the system configuration andby selecting the technologies that meet the current
objectives.
3. Enabling technologies in MDRU architecture
The major enabling technologies adopted for the
MDRU architecture are shown in Fig. 2. The MDRU
actually acts as a movable telephone office and/or
datacenter. It accommodates network equipment,
servers, and storage devices. They are interconnected
to form a LAN in the unit. The LAN is extended tothe surrounding area by way of a Wi-Fi-based accessnetwork to reach customer devices such as smartphones and personal computers. In the server, application software for ICT services such as Internet
protocol (IP)-based telephony is installed [8]. Several
new technologies allow the MDRU to instantly
respond to new demands for ICT services in thedisaster-affected area. Details of the technologies arereported in the other Feature Articles in this issue.
4. MDRU R&D project
NTT Network Innovation Laboratories launched an
R&D project aimed at realizing the MDRU architecture in collaboration with NTT Communications
Corporation, Tohoku University, and Fujitsu Limited,
and with the support of the Ministry of Internal affairs
and Communications of Japan. The prototype
MDRUs developed in the project are shown in Fig. 3.
Several types of MDRUs that have different sizes andresource capabilities have been developed. TheFeature Articles

Convenient IP-PBX
Offers voice communication
to users in disaster area

Media storage andtransmission
Efficient content storage
based on layered coding
technology

Efficient refugee
management system
Refugee data acquisition
using IC card and digital
camera of tablet devices

Monitor/ControlAccesscontrolfor WANinterface

DB

APL

APL

MDRU usage guidelines
Provides a way to optimize
installation process

APL

Network for voice communication
Network for a private organization

Accesscontrolfor LANinterface

Network for a local government
Reconfigurable network

MDRU
Architecture as asystem andspecifications ofcomponent modules

Wireless access network
Rapid access network
configuration based on AP’scontrol over 920-MHz
sensor network

Plug&Play high-speed
optical link
Connection of MDRU to
WAN using remaining
optical fibers

Remote monitor/control
of MDRU

AP: access point
APL: application
DB: database
IP-PBX: Internet protocol-based private branch exchange
LAN: local area network
WAN: wide area network

Fig. 2. Major enabling technologies applied in MDRU architecture.

MDRUs have been subjected to several feasibility
studies and proof-of-concept experiments such as
those to confirm the operation of major functions.
The specifications of the latest prototype MDRU,
which is a vehicle called the ICT Car, are summarizedin Table 1. The ICT Car can deliver ICT services forfive consecutive days without external electric power,
as it hosts an electric power system consisting of agenerator and batteries and an energy-saving air conditioning system based on latent heat material. The
ICT Car carries several wireless equipment modules
such as Wi-Fi access point equipment and wirelesstransceivers for fixed point-to-point wireless links.
These wireless modules are distributed in the areasurrounding the ICT Car and used to form the widest
possible wireless access network.



5. MDRU installation experiment as
a proof of concept
We conducted an MDRU installation experimentusing ICT Car at the University of Aizu in Fukushima
Prefecture to prove our concept. Some pictures of theexperiment are shown in Fig. 4. In Fig. 4(a), project
members take the wireless modules from the ICT Car
and prepare to distribute them. In Fig. 4(b), someproject members are setting up a Wi-Fi access point
module by connecting the module to its antenna.
The experimental results are shown in Fig. 5, whichplots the relationship between the installation patterns of the wireless access network and the measured
times necessary to start delivering a service. We
experimentally confirmed that it was possible for us
to start delivering ICT services within 40 minutes
after the arrival of the ICT Car at the intended site.
When the wireless access network was extended by a
NTT Technical Review

Resource capacity, robustness

Large

Feature Articles

Function/area extension by
networking multiple
MDRUs

Large MDRU (2012)

Attaché case type MDRU

Miniaturization

IP-PBX

Mid-sized MDRU (2012)

Battery

Wi-Fi AP

Unit miniaturization by function selection
ICT Car

Small

Small MDRU (2013)
Modularized MDRU
Small

Large

Mobility, extensibility, flexibility

Fig. 3. Roadmap of MDRU development.

Table 1. Specifications of ICT Car.
Item

Details

Base carToyota Hiace (net capacity: 1 ton)

Power source

Gasoline electric generator, lithium-ion buttery unit,
electric power input from outside

Air conditioning

Energy-saving air conditioning system based onlatent heat material

Number ofracks

2 (8U 19-inch racks)

Servers- Application server (e.g. for IP-PBX)- Server for virtual network control- Server for remote operation- Server/storage for hosting/housing

Link to WAN

1G Ethernet media converter

Access network Wi-Fi (2.4G/5G), wired (1G/100M Ethernet), FWA(5-GHz/25-GHz band)
Network control

Wide-area ubiquitous network (920-MHz band,
sensor network)

FWA: fixed wireless accessfew kilometers by linking several wireless modules,
it took about 140 minutes in total, regardless of thetype of area extension. These times meet our MDRU
requirement of delivering service within a few hours
after arrival. Thus, we can conclude from the experiments and trials that the proposed MDRU architecture is highly effective.
Vol. 13 No. 5 May 2015

6. Summary and future work
This article introduced the MDRU architecture,
which was developed to resolve the critical issues
appeared after the 2011 earthquake, and describedseveral achievements of the MDRU R&D project.
The feasibility of the proposed MDRU concept hasFeature Articles

(a)

(b)

Fig. 4. MDRU installation experiment; (a) preparation for wireless module distribution, and (b) setup of Wi-Fi module.

Elapsed time from unit arrival (min.)(1) Single unit

Wi-Fi

Wi-Fi

Wi-Fi

140

Distribution and setup of Wi-Fi
modules (60 in case of
4 modules)
Elapsed time depends on# of modules

100
80
60

20
0

Turn on the servers/software.
(30)(3) FWA area extension

Wi-Fi

Confirm Wi-Fi link. (20)

120

40

(2) Wi-Fi area extension

Preparation of Wi-Fi
modules (60)

FWA

Wi-Fi

Confirm FWA link. (20)(4) Unit collaboration
FWA

Confirm the network
establishment. (20)Distribution and setup of Wi-Fi, Turn on FWA. (20)
FWA modules (60 in case of
4 modules)
Elapsed time depends onConnect FWA modules to# of modules
MDRUs and establish
wireless links among
Preparation of Wi-Fi,
MDRUs. (90)
FWA modules (60)Install MDRU and turn on the battery. (10)Transportation of MDRU to the target area
Small

Local area coverage

Large

Fig. 5. Patterns of LAN extension and measured installation times.

already been confirmed, and the project is now moving toward the commercialization phase. Discussionof the global standardization of the MDRU architecture in ITU-T (International Telecommunication
Union, Telecommunication Standardization Sector)
SG (Study Group) 15 started in 2014. A feasibility
study of our MDRU architecture in an actual disasterarea has also been conducted in the Philippines,
where MDRU sets were used to provide services topeople in an area affected by a typhoon.
There are other goals to be accomplished in the
MDRU R&D project, so our R&D activities will continue. Our final goal is to apply MDRUs domesticallyas well as globally and to contribute to saving thelives of people in disaster areas in the future.
Acknowledgement
Part of the work in this article is being conductedunder the national projects, R&D on the reconfigurable communication resource unit for disasterrecovery and R&D of “Movable ICT Units” for emergency transportation into disaster-affected areas andmulti-unit connection, both supported by the Ministryof Internal Affairs and Communications of Japan.

NTT Technical Review

Feature Articles

References
[1]

[2]

[3]

[4]

T. Sakano, Z. M. Fadlullah, T. Kumagai, A. Takahara, T. Ngo, H.
Nishiyama, H. Kasahara, S. Kurihara, M. Nakazawa, F. Adachi, and
N. Kato, “Disaster Resilient Networking: a New Vision Based on
Movable and Deployable Resource Units (MDRUs),” IEEE Network,
Vol. 27, No. 4, pp. 40–46, 2013.
Y. Shimizu, Y. Suzuki, T. Kumagai, and K. Goto, “Wireless AccessNetwork System Using M2M Wireless Access for MDRU,” NTT
Technical Review, Vol. 13, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa2.html
T. Komukai and T. Sakano, “High-speed and Plug-and-play Optical
Interconnection for MDRUs,” NTT Technical Review, Vol. 13, No. 5,2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa3.html
T. Nakachi, S.-Y. Kim, A. Okada, and T. Fujii, “A Media Storage andTransmission System Using MDRUs,” NTT Technical Review, Vol.

Toshikazu Sakano†

Senior Research Engineer, Supervisor, Photonic Transport Network Laboratory, NTT Network Innovation Laboratories.
He received the B.E., M.E., and Ph.D. in electronics engineering from Tohoku University,
Miyagi, in 1985, 1987, and 1998, respectively.
He joined NTT Transmission Systems Laboratories in 1987. Since joining NTT, he has been
active in several R&D fields including opticalsignal processing for high-performance computing systems, super-high-definition imaging systems, photonic network architectures, and largecapacity optical transmission systems. Since theGreat East Japan Earthquake in March 2011, hehas been engaged in R&D of resilient ICT infrastructure available in disaster situations. He
received the Young Engineer Award from theInstitute of Electronics, Information and Communication Engineers (IEICE) in 1994 and theBest Paper Award from the Institute of Electricaland Electronics Engineers (IEEE)’s International
Conference on Computer Design in 1990 and
1993. He is a Senior Member of IEICE and the
Optical Society of America (OSA), and a member of IEEE.
†As of January 2015, he is a director of Advanced
Telecommunications Research Institute International (ATR).

Vol. 13 No. 5 May 2015

[5]

[6]

[7]
[8]

13, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa4.html
S. Kotabe, T. Sakano, and T. Komukai, “ICT Service for MDRUs,”
NTT Technical Review, Vol. 13, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa5.html
H. Nishizawa and T. Sakano, “Overseas Deployment of MDRU: ITU
Project in the Philippines, and MDRU Standardization Efforts,” NTT
Technical Review, Vol. 13, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa6.html
T. Sakano, “An ICT Network which is Resilient against Catastrophic
Disasters,” The journal of Reliability Engineering Association ofJapan, Vol. 34, No. 8, pp. 513–518, 2012 (in Japanese).
T. Sakano, S. Kotabe, T. Komukai, and A. Takahara, “Movable and
Deployable ICT Resource Unit for Instant Delivery of Local ICT
Services,” Proc. of APMC 2014, TH4A-3, Sendai, Japan, Nov. 2014.

Satoshi Kotabe

Senior Research Engineer, Media Innovation
Laboratory, NTT Network Innovation Laboratories.
He received the B.E. and M.E. in electronicengineering from Ibaraki University in 1993 and1995, respectively. He joined NTT in 1995. His
work has focused mainly on high-speed data
communication network architectures. His current research interests include the protocols andarchitectures of disaster relief networks. He is amember of IEICE.

Tetsuro Komukai

Senior Research Engineer, Photonic Transport
Network Innovation Laboratory, NTT Network
Innovation Laboratories.
He received the B.E. in electrical engineeringand the M.E. in electrical and communicationengineering from Tohoku University, Miyagi, in
1986 and 1988, respectively, and the Ph.D. inelectronics engineering from the University ofTokyo in 2004. He joined NTT Transmission
Systems Laboratories in 1988 and engaged in
R&D of fiber amplifiers, fiber Bragg gratings,
and optical transmission systems. He is currently
focusing on R&D of resilient ICT infrastructure
available in disaster situations. He is a Senior
Member of OSA, and a member of IEICE, IEEE,and the Japan Society of Applied Physics.

Feature Articles: Movable and Deployable ICT Resource Unit—
Architecture for Quickly Responding to Unexpected ICT Demand

Wireless Access Network System
Using M2M Wireless Access for
MDRU
Yoshitaka Shimizu, Yasuo Suzuki, Tomoaki Kumagai,
and Kazuto Goto
Abstract

NTT Network Innovation Laboratories has been developing the Movable and Deployable ICT
Resource Unit (MDRU) that enables us to quickly reestablish information and communication technology (ICT) services in disaster-stricken areas. In this article, we introduce a novel MDRU radio functionthat constructs a Wi-Fi access network quickly and flexibly around the MDRU by using machine-tomachine wireless access as the control link.
Keywords: M2M wireless access, remote control, Wi-Fi network

1. Introduction
Smartphones with Wi-Fi capability have rapidly
come into widespread use. They enable users toaccess the Internet outdoors and indoors via wireless
local area networks (WLANs). Consequently, thenumber of users who access the Internet with smartphones is increasing. We expect that there will be
more and more opportunities to use Wi-Fi in the near
future since a lot of Wi-Fi access points (APs) will be
installed to strengthen connectivity prior to the 2020
Tokyo Olympic Games.
In view of the popularity and consequent importance of Wi-Fi, we must consider how to recreate
Wi-Fi services after a disaster strikes. It is necessary
to rapidly and flexibly deal with unexpected network
failures such as those caused by the severing of optical fiber to Wi-Fi APs, which might occur after adisaster. For example, when several access links arebroken and a network operator tries to recreate themby using Wi-Fi multi-hop connections such as wireless distribution system (WDS)*1 links, the corresponding Wi-Fi APs must be reset so as to establish
multi-hop connections by linking neighboring APs to
one another. Moreover, the conventional solutiondemands that users and administrators reset each AP
according to the surrounding radio link situation.
This is not easy, and it takes too long to reestablish
Wi-Fi networks. To solve this problem, NTT Network Innovation Laboratories has been developing
the Movable and Deployable ICT Resource Unit
(MDRU) [1], which allows information and communication technology (ICT) services to be reestablished quickly in disaster areas. As a key MDRU
wireless function, we are developing a system thatenables rapid construction of a wireless access network by using machine-to-machine (M2M) wirelessaccess*2 as the control link. This will make it possible
for users to access the Internet via the Wi-Fi functionof their smartphone.

*1	 WDS: A wireless distribution system used to form multi-hop
connections.
*2 M2M wireless access: A machine-to-machine wireless accesssystem that is based on the standard method used in private wireless systems but has an added function that enables it to control
the APs and wireless terminals (WTs) from a network.

NTT Technical Review

Feature Articles

Relay

link: 5

GHz

Access link: 2.4 GHz
Smartphone with
Wi-Fi function

FWA
Hz

0M

25 GHz

nk

l li

o
ntr

2
:9

Co

Solar panel

FWA
M2M BS

Network

Wi-Fi AP

Battery

AP: access point
BS: base station
FWA: fixed wireless access
PC: personal computer

M2M
wirelessterminal

Mini PC
Control
serverMovable Wi-Fi AP module

Fig. 1. Wireless access network system using M2M wireless access.

2. Wireless access network system using M2M
wireless access as the control link
The wireless access network system using M2M
wireless access is shown in Fig. 1. This system controls the Wi-Fi APs attached to the M2M wirelessterminal from the M2M base station (BS) installed bya carrier in the disaster area via an M2M wirelessaccess link. Constructing relay links among the APs
provides wide area coverage for communication
around the area where the M2M BS is installed.
Therefore, the system has two noteworthy features.
The first is easy deployment. The complicated Wi-Fi
AP settings traditionally performed by engineers areunnecessary due to the remote control capability
using M2M wireless access from the MDRU. The
system also provides flexibility in establishing connections. If we try to cover the area by using only
Wi-Fi APs, many Wi-Fi APs would be occupied byrelay traffic. This would degrade throughput due toincreases in the transmission delay and processing
load. To avoid this situation, the system employs
entrance links based on fixed wireless access (FWA)*3
systems to reduce the number of relay Wi-Fi APs andto cover a wider area.
The MDRU prototype called the ICT Car has several modules such as an M2M BS module, a movable
Wi-Fi AP module with solar panel and battery, and an
Vol. 13 No. 5 May 2015

FWA module with solar panel and battery. The Wi-Fi
AP and FWA modules can be used even if the external power supply is down. After a disaster, the ICT
Car arrives at the affected area, and these modules,transported by the ICT Car, are positioned up to
500 m away from the ICT Car. Since the remote control from the ICT Car is used to construct the Wi-Fi
access network, we can reestablish the ICT environment [2] effectively and quickly with very few people.
3. Technical problems and solutions
If the MDRU is to control the Wi-Fi access network
quickly and flexibly, it is essential that large numbersof WLAN APs be properly controlled in a shortperiod by means of M2M wireless access. Unfortunately, M2M wireless access uses very low transmission rates ranging from several kilobits per second toseveral hundred kilobits per second in order to keep
the transmission power of the WTs low and to achieve
wide-area coverage, so it takes a comparatively longtime to transmit the data to control the Wi-Fi APs andto transmit information from the Wi-Fi APs. To solve
this problem, we need a means of effectively*3 FWA: A system that enables a radio link to be connected between
two points located far away from each other.

Feature Articles

Control server side

Wi-Fi AP side

Controlalgorithm
Wi-Fi APs

Commoncommand library

Commandinterpreter

Management of
wireless NW
Command/Data
processing

M2M BS

M2M WT

Commanddictionary

TE emulator
Mini PC

Control server

Movable Wi-Fi AP module

NW: network
TE: terminal equipment

Fig. 2. Prototype platform.

controlling M2M wireless access. Moreover, we needto control a variety of Wi-Fi AP devices, but this is noteasy to do since the devices may be from different
vendors. We dealt with this by developing a software
wrapper technology that enables different WLAN AP
devices to be controlled in a common manner.
To assess the wireless access network system, webuilt a prototype platform as shown in Fig. 2. The
platform consists of an M2M BS, a control server,
and movable Wi-Fi AP modules including an M2M
WT, a mini personal computer (PC), and Wi-Fi APs.
To control the widest possible range of Wi-Fi AP
devices, the control server has a specific command
library with a set of common commands. When theoperator issues a command to the Wi-Fi APs, the control server translates the control command into thecorresponding common commands by referring to
the library, and then sends the commands to the Wi-Fi
AP modules via M2M wireless access. When the WiFi AP module receives the commands, the commandinterpreter of the mini PC converts the commands
into vendor-specific commands that correspond to the
Wi-Fi device. The platform transmits only criticalinformation in both the uplink and downlink in orderto minimize the depletion of wireless resources andreduce the transmission delay. In the uplink, the only
necessary information to control is extracted from theinformation acquired from the Wi-Fi AP in a command interpreter of the mini PC and then transmitted
to the control server via M2M wireless access. In
contrast, in the downlink, multiple vendor commands
are assigned to a common command, which mini

Table 1. Main specifications of M2M wireless access.
Frequency band

280-MHz band
(Experimental purposes only)

Transmission power

BS: 1 W

Modulation scheme

π/4 –Shift QPSKDemodulation scheme

Uplink: coherent detection
Downlink: differential detection

Access method

TDMA/TDD

Forward error correction

Convolutional coding (R = 1/2)
/ Viterbi decoding

WT: 10 mW

QPSK: quadrature phase-shift keying
TDD: time-division duplex
TDMA: time-division multiple accessmizes the number of control sequences passed to the
Wi-Fi AP modules.
4. Field experiments and evaluations
We conducted field experiments using our prototype platform at the Tohoku University campus. The
platform employs the 280-MHz band, so we conducted field experiments using that band. We usedeight different Wi-Fi APs from two vendors, Vendor
A and B, in the experiments in order to evaluate theperformance of our proposed system. The main
specifications of M2M wireless access are listed inTable 1. First, we confirmed that the coverage area
was over 400 m by actually controlling Wi-Fi APsthat were positioned about 430 m from the MDRU.
NTT Technical Review

With 1 AP

With 2 APs(Maximum number of
WDS links = 1)

With 5 APs(Maximum number of
WDS links = 4)

With 3 APs(Maximum number of
WDS links = 2)

With 6 APs(Maximum number of
WDS links = 5)

Time to construct Wi-Fi network (min.)Feature Articles

30
25
20
15
10
Vendor A
50

Vendor B
1

2

3

4

5

6

7

8

Number of Wi-Fi APs
With 7 APs(Maximum number of
WDS links = 6)

With 8 APs(Maximum number of
WDS links = 7)

Fig. 4. Time required to construct Wi-Fi access network.

WDS: wireless distribution system

5. Future work

Fig. 3. Measured network topologies.

We evaluated how effective the transmission technique was by collecting wireless environment information of a Wi-Fi AP on our platform before measuring the transmission time. Without our technique,data capture took 167 s, and it took 147 s to transmit
the data so gathered. With our technique, data capture
took 68 s, and transmission took 45 s. The volume of
information was reduced by 1550 bytes.
Next, we constructed a Wi-Fi access network using
two kinds of Wi-Fi AP devices to find out whether or
not our platform could control different Wi-Fi AP
devices. The network topologies we implemented areshown in Fig. 3. We selected the topology in which
the number of WDS links becomes the maximum
given the number of Wi-Fi APs. We conducted wireless environment information collection, SSID *4(service set identifier) setting, and WDS setting, and
we also issued link confirmation commands in order
to construct the Wi-Fi access network. The time taken
to construct the Wi-Fi network versus the number of
Wi-Fi APs is shown in Fig. 4. The results confirm thatthe common commands of our platform allowed different Wi-Fi AP devices to be controlled; moreover, a
Wi-Fi access network with eight Wi-Fi APs was able
to be constructed within 30 minutes. It is possible toshorten this time by adjusting the timer to wait for
responses in the Wi-Fi module.

We plan to conduct additional field experiments
using the 920-MHz band instead of the 280-MHz
band in Japan as well as overseas [3] in order toevaluate the effectiveness of the system.
Acknowledgment
Part of the work described in this article is being
conducted under the national projects, R&D on thereconfigurable communication resource unit fordisaster recovery and R&D of “Movable ICT Units”
for emergency transportation into disaster-affectedareas and multi-unit connection, both supported by
the Ministry of Internal Affairs and Communicationsof Japan.
References
[1]

[2]

[3]

T. Sakano, S. Kotabe, and T. Komukai, “Overview of Movable and
Deployable ICT Resource Unit Architecture,” NTT Technical Review,Vol. 13, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa1.html
S. Kotabe, T. Komukai, and T. Sakano, “ICT Service for MDRUs”
NTT Technical Review, Vol. 13, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa5.html
H. Nishizawa, T. Sakano, T. Takahashi, and S. Yamaguchi, “Overseas
Deployment of MDRU: ITU Project in the Philippines, and MDRU
Standardization Efforts,” NTT Technical Review, Vol. 13, No. 5,2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa6.html*4 SSID: An identifier of Wi-Fi APs regulated by standardization.

Vol. 13 No. 5 May 2015



Feature Articles

Yoshitaka Shimizu

Senior Research Engineer, NTT Network Innovation Laboratories.
He received the B.E. and M.S. in electricalengineering from Tokyo Institute of Technology
in 1995 and 1997, respectively. He joined NTT
Wireless Systems Laboratories in 1997. His current work is in the area of wireless access systems.

Yasuo Suzuki

Research Engineer, NTT Network Innovation
Laboratories.
He received the B.E., M.E., and Dr. in engineering from Saitama University in 1989, 1991,
and 2006, respectively. In 1991, he joined NTT
Radio Communication Systems Laboratories. He
has been conducting research on synchronization
schemes and interference cancellation schemes
for spread-spectrum communication systems andsoftware-defined radio systems. His current
research interests include high speed signal processing and high speed wireless communication
systems.

Tomoaki Kumagai

Director of Wave Engineering Laboratories,
Director of Research Planning Section, Social
Media Research Laboratory Group, Advanced
Telecommunications Research Institute International (ATR).
He received the B.E. and M.E. in electrical andcommunication engineering, and the Ph.D. in
information science from Tohoku University,
Miyagi, in 1990, 1992, and 2008, respectively.
Since joining NTT in 1992, he has been engaged
in research and development of wireless communication systems. He moved to ATR in July
2014. He received the Young Engineer Award
from the Institute of Electronics, Information andCommunication Engineers (IEICE) in 1999. He
is a member of IEICE and IEEE (Institute ofElectrical and Electronics Engineers).

Kazuto Goto

Section Chief, Marketing and Service Development Department, NTT Broadband Platform,Inc.
He received the B.E. and M.E. in knowledge
engineering & computer sciences from Doshisha
University, Kyoto, in 2006 and 2008, respectively. He joined NTT Network Innovation Laboratories in 2008 and studied wireless access systems.
He joined NTT Broadband Platform Inc. in 2014
and is currently engaged in the development of
Wi-Fi APs.

NTT Technical Review

Feature Articles: Movable and Deployable ICT Resource Unit—
Architecture for Quickly Responding to Unexpected ICT Demand

High-speed and Plug-and-play
Optical Interconnection for MDRUs
Tetsuro Komukai and Toshikazu Sakano
Abstract

After a Movable and Deployable ICT Resource Unit (MDRU) is installed and local ICT (informationand communication technology) services are established in a disaster-affected area, reestablishing communication service between the disaster-affected area and undamaged areas will be strongly desired by
the people in the disaster-affected area. We propose to establish a communication link between the
MDRU and the backbone network by connecting 100-Gbit/s digital coherent transponders to the ends ofundamaged underground optical cable.
Keywords: movable and deployable ICT resource unit, digital coherent technology, plug and play

1. Introduction
The Movable and Deployable ICT Resource Unit
(MDRU) can be easily transported to damaged areas
and used to quickly establish local information andcommunication technology (ICT) services once it isinstalled. A Wi-Fi based access network is formed
with a radius of several hundred meters from the center of the MDRU; it allows public and municipal
employees to communicate with others in the area. In
addition, because the MDRU has a datacenter function, it can provide various custom ICT services tolocal government, hospitals, and the police and fire
departments.
However, these services are available only within
the limited area around the MDRU, and another strategy is necessary to reestablish communications withthose outside the damaged area. There are two main
approaches to connect an MDRU to the backbone
network. One is to use satellite communications, andthe other is to use optical communications. Eachapproach has advantages and disadvantages, so theselection depends on the situation.
Satellite interconnection makes it possible to avoid
the physical difficulties present in the disaster area,
although the transmission capacity is limited. For
example, only a limited number of conversations canbe conducted simultaneously between people in thedamaged area and people in undamaged areas. In
contrast, while optical communications offer massive
capacity, there may be few facilities available if thedamage is severe. However, optical fiber cables laid
underground are thought to be robust against disasters. In fact, we (the NTT Group) found that many
optical fiber cables remained viable even after all
surface structures and equipment had been washedaway by the tsunami after The Great East Japan
Earthquake. This means that optical links could beestablished if we could use the undamaged opticalfiber cables.
We recently proposed a method to connect an
MDRU to the backbone network by using opticalfiber cables laid underground [1]. In this article, we
explain our method and describe a proof-of-concept
demonstration.
2. Optical interconnection requirements:
MDRU to backbone network
Several difficulties arise when connecting an
MDRU to the backbone network via optical links
established on optical fibers, as follows.
(1)	It is very difficult to immediately obtain comprehensive information on cable parameters(fiber type, length, etc.) in the damaged area.
(2)	Transmission capacity will need to be expanded
NTT Technical Review

Feature Articles

10 × 10 GbE
SFP+
SFP+
SFP+

OTU
framer/FEC

Y
Precoder

X
I

LD

Q I

Q

100-Gbit/s
PDM QPSKIQ Mod.

100-Gbit/s PDM-QPSK transmitter

SFP+

DSP
+
Decoder

OTU
framer/
FEC

ADC
ADC
ADC
ADC

B-PD
B-PD
B-PD
B-PD

90 deg.
hybrid90 deg.
hybrid

LO

SFP+
SFP+

PBS

10 × 10 GbE
100-Gbit/s
PDM QPSK

100-Gbit/s PDM-QPSK receiver
LD: laser diodeLO: local oscillator
PBS: polarization beam splitter

Fig. 1. Configuration of prototype 100-Gbit/s digital coherent transponder.

because the standard voice service will be
replaced by a visual information service thatneeds a wider bandwidth as reconstruction progresses.
(3)	Prompt and flexible reconfiguration of the optical network will be needed in the damaged area
because the situation can easily change. Thismeans that the optical path can often change.
(4)	When we connect an MDRU to a faraway datacenter in an undamaged area by optical networking only, long-distance optical transmission is needed, which requires chromatic dispersion compensation.
In considering these difficulties, we arrived at theconclusion that a 100-Gbit/s digital coherent transponder should be installed in both the MDRU and aworking telecommunication building to enable optical interconnection. A digital coherent transponder
can equalize optical signal waveforms automaticallyby electrically compensating the chromatic dispersion of fibers, so it is therefore expected that opticalinterconnection can be immediately established byconnecting the transponders to the ends of the fiber
cables, even though the fiber parameters may be
unknown. In addition, the optical interconnection
will be immediately reestablished after switching
optical fiber cables for rerouting.
To verify the above concept, we developed a prototype of a 100-Gbit/s digital coherent transponder andVol. 13 No. 5 May 2015

experimentally confirmed the robust and immediateconnection by virtue of its plug-and-play functionality.
3. Optical channel recovery experiment
The configuration of our prototype 100-Gbit/s digital coherent transponder for an MDRU is shown in
Fig. 1. The prototype is based on a standard 100-Gbit/s
polarization-division multiplexing (PDM) quadraturephase-shift keying (QPSK)*1 transponder [2] and cancompensate the maximum chromatic dispersion (CD)of 40,000 ps/nm. The transponder accommodates ten
channels of 10-Gbit/s Ethernet (10GbE) client data,
and ten SFP+ (small form-factor pluggable+) modules*2 can be installed on the input/output interface
part. The 10GbE client data are multiplexed into 100Gbit/s optical transport network (OTN) signals*3
through an optical-channel transport unit 4 (OTU4)
framer and with forward error correction (FEC)*1	 QPSK: A multi-level modulation scheme that uses four points on
the constellation diagram and encodes two bits per symbol withfour phases.
*2 SFP+ modules: Optical transceiver modules for 10GbE interconnections.
*3 OTN signals: Signals that are used in the optical transport network
standardized by ITU-T (International Telecommunication Union,
Telecommunication Standardization Sector). Ethernet signals are
mapped to OTN signals through the OTU framer.

Feature Articles

Transmitter

10 GbE

100-Gbit/s
transponder astransmitter

100-Gbit/s
PDM-QPSK
32-km
GIF

10-GbE
analyzer

ReceiverOpticalswitch
10 GbE

100-Gbit/s
transponder asreceiver75-km SMF

100-Gbit/s
PDM-QPSK

10-GbEsignal power
GIF: graded-index fiber
SMF: single-mode fiber

Fig. 2. Experimental setup for optical route switching of 100-Gbit/s signal.

overhead. The data are realigned to 4 × 32-Gbit/s
sequences and fed into an optical IQ (I: In-phase, Q:
Quadrature) modulator for QPSK modulation andpolarization multiplexing. The transmitted 100-Gbit/s
PDM-QPSK signal is received by a digital coherent
receiver; I and Q data for each polarization are
obtained with a polarization-diversity 90 degree optical hybrid and balanced photodetectors (B-PDs), anddigitized with a four-channel analog-to-digital converter (ADC). In the digital signal processing (DSP),
CD compensation, polarization demultiplexing andadaptive polarization mode dispersion (PMD) equalization, and frequency-offset compensation and carrier-phase recovery are carried out for the 4 × 32Gbit/s data, followed by error correction and demapping to 10 GbE.
We evaluated how fast the optical channel could berecovered when the 100-Gbit/s transmission link was
switched between different types and lengths offibers by a mechanical fast optical switch whose
switching time was less than 1 ms. The experimental
setup is shown in Fig. 2. The 10GbE client data aresupplied by a 10GbE analyzer and converted to 100Gbit/s signals in the transmitter. The transmitted signals are received, and the converted 10GbE client
data are fed via another short fiber to the 10GbE analyzer, which counted the received bytes with a resolution of 1 ms. This enabled us to evaluate the influenceof link switching on the throughput of the client
10GbE data. The point at which we measured the
10GbE signal power is also shown in Fig. 2 by thearrow in the lower left of the figure.
We evaluated how fast the optical channel could bereestablished when the link was switched from a 75km single-mode fiber (SMF) to a 32-km graded-index
fiber (GIF) and vice versa. The evolution of thereceived 10GbE optical signal level is shown in Fig. 3
and Fig. 4. After the link was switched, the 10GbE
signal output was shut down and remained quiescentfor 27 ms until the signal level returned to normal.
This indicates that once the channel was disconnected, the DSP was able to complete channel re-estimation and synchronization within 27 ms. The outage
time is the same in Fig. 3 and Fig. 4, which indicatesthat recovery time is independent of the fiber type andlength.
For comparison, we measured the evolution of thereceived 10GbE data traffic associated with theswitching by using a 10GbE analyzer; the results areshown in Fig. 5 and Fig. 6. The horizontal axis is theelapsed time after channel switching, and the verticalaxis shows the net bit rate calculated from the numberof bytes received without failure. The 10GbE traffic
recovers after 30 ms. The 3-ms difference from Fig. 3
and Fig. 4 may be due to the processing time in the
10GbE receiver module. Also, it is concluded that a
100-Gbit/s digital coherent transponder can compensate the modal dispersion*4 of a GIF about 30 km
long.
*4 Modal dispersion: A distortion mechanism occurring in multimode fibers in which the signal is spread in time because thepropagation velocity of the optical signal is not the same for allmodes. Although GIF is a kind of multimode fiber, the index profile of the core is designed to reduce the modal dispersion.

NTT Technical Review

Feature Articles

32-km GIF

32-km GIF

Signal power (arb. unit)

Signal power (arb. unit)

75-km SMF

27 ms

–40

–20

0

20

40

27 ms

60

–40

–20

0

Time (ms)40

60

Fig. 4. E
 volution of received 10GbE signal level(32-km GIF 75-km SMF).

32-km GIF

32-km GIF

10

75-km SMF

10
Received bit rate (Gbit/s)

Received bit rate (Gbit/s)

20

Time (ms)Fig. 3. Evolution of received 10GbE signal level(75-km SMF 32-km GIF).

75-km SMF

75-km SMF

8
6
30 ms

4
2
0

8
6
30 ms

4
2
0

–40

–20

0

20

40

60

Time (ms)

–40

–20

0

20

40

60

Time (ms)Fig. 5. Evolution of received 10GbE data traffic(75-km SMF 32-km GIF).

Fig. 6. E
 volution of received 10GbE data traffic(32-km GIF 75-km SMF).

The measured switching performance suggests thatthe transponder offers true plug-and-play functionality and that fiber parameters do not need to be measured. Thus, the transponder is expected to be effective after disasters for interconnecting MDRUs to the
backbone network through underground optical fiber
cables.

based on digital coherent technology, an MDRU canbe immediately connected to the working backbone
network via an undamaged underground optical fiber
cable. We note that not all MDRUs will be sited close
to optical fiber that offers unbroken connection to the
backbone, as they will usually be placed next toevacuation centers or public facilities. Thus, we will
have to interconnect the MDRUs. If there is no physical obstruction between two MDRUs, we can connect them by fixed wireless access. However, when
physical obstruction is unavoidable, one alternative isto reuse parts of the underground optical fiber cable

4. Perspective on optical interconnection
for MDRU
In conclusion, with the plug-and-play functionality
Vol. 13 No. 5 May 2015



Feature Articles

that are still viable.
To realize the above optical interconnection using
underground cables, we need to obtain prior agreement from communication carriers and to carry out
technical preparations for the connections to the
backbone network. For example, we have to obtainagreement as to how or where to set a transponder ina telecommunication building. It is also necessary todevelop a way of finding or selecting optical cables indisaster areas and protocols to confirm the corresponding cables in working telecommunicationbuildings. This will definitely require the support andassistance of communication carriers. In addition, we
will have to consider using the optical cables of noncarriers such as local governments.

technology. We also discussed problems that remain
to be solved from a practical application perspective.
Acknowledgments
Part of the work in this article is being conductedunder the national projects, R&D on the reconfigurable communication resource unit for disasterrecovery and R&D of “Movable ICT Units” for emergency transportation into disaster-affected areas andmulti-unit connection, both supported by the Ministryof Internal Affairs and Communications of Japan.
References[1]

5. Summary
We proposed the application of digital coherent
technology to interconnect MDRUs in a disaster areawith the backbone network via working telecommunication buildings and underground optical fiber
cable. We experimentally confirmed the plug-andplay functionality achieved using digital coherent

Tetsuro Komukai

Senior Research Engineer, Photonic Transport
Network Laboratory, NTT Network Innovation
Laboratories.
He received the B.E. in electrical engineeringand the M.E. in electrical and communicationengineering from Tohoku University, Miyagi, in
1986 and 1988, respectively, and the Ph.D. inelectronics engineering from the University ofTokyo in 2004. He joined NTT Transmission
Systems Laboratories in 1988 and engaged in the
research and development (R&D) of fiber amplifiers, fiber Bragg gratings, and optical transmission systems. He is currently focusing on R&D
of resilient ICT infrastructure available in disaster situations. He is a Senior Member of the
Optical Society of America (OSA), and a member of the Institute of Electronics, Information,
and Communication Engineers of Japan (IEICE),
the Institute of Electrical and Electronics Engineers (IEEE), and the Japan Society of Applied
Physics (JSAP).

[2]

T. Komukai, H. Kubota, T. Sakano, T. Hirooka, and M. Nakazawa,“Plugand-Play Optical Interconnection Using Digital Coherent Technology
for Resilient Network Based on Movable and Deployable ICT
Resource Unit,” IEICE Transactions on Communications, Vol. E97-B,
No. 7, pp. 1334–1341, Jul. 2014.
Y. Miyamoto, A. Sano, E. Yoshida, and T. Sakano, “Ultrahigh-capacity Digital Coherent Optical Transmission Technology,” NTT Technical Review, Vol. 9, No. 8, Aug. 2011.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2011
08fa2.html

Toshikazu Sakano†

Senior Research Engineer, Supervisor, Photonic Transport Network Laboratory, NTT Network Innovation Laboratories.
He received the B.E., M.E., and Ph.D. in electronics engineering from Tohoku University,
Miyagi, in 1985, 1987, and 1998, respectively.
He joined NTT Transmission Systems Laboratories in 1987. Since joining NTT, he has been
active in several R&D fields, including opticalsignal processing for high-performance computer systems, super-high-definition imaging systems, photonic network architectures, and largecapacity optical transmission systems. Since theGreat East Japan Earthquake in March 2011, hehas been engaged in R&D of resilient ICT infrastructure available in disaster situations. He
received the Young Engineer Award from IEICE
in 1994 and the Best Paper Award from IEEE’s
International Conference on Computer Design in1990 and 1993. He is a Senior Member of OSA
and IEICE, and a member of IEEE.
†As of January 2015, he is a director of Advanced
Telecommunications Research Institute International (ATR).

NTT Technical Review

Feature Articles: Movable and Deployable ICT Resource Unit—
Architecture for Quickly Responding to Unexpected ICT Demand

A Media Storage and Transmission
System Using MDRUs
Takayuki Nakachi, Sun Yong Kim, Atsushi Okada,and Tatsuya Fujii
Abstract

Developing information and communication technology (ICT) networks and services that are resilient
to disasters is a critical task. NTT Network Innovation Laboratories is promoting innovative research anddevelopment on a transportable ICT node called the Movable and Deployable ICT Resource Unit
(MDRU), which is designed to promptly recover ICT services after a disaster. In this article, we introduce a media storage and transmission system based on the use of MDRUs. It efficiently provides information such as text and image/video data to people in disaster areas in circumstances when ICT resources are constrained such as when network bandwidth is limited or storage failures occur. We demonstrated its feasibility in a field trial.
Keywords: layered coding, distributed storage, image/video transmission

1. Introduction
The Great East Japan Earthquake of March 11,2011 damaged or completely destroyed many information and communication technology (ICT)
resources, which demonstrated that the developmentof resilient ICT networks and services is a criticalissue demanding urgent attention. Immediately aftera disaster, it is important to rapidly share accurate
information. In addition to text data, image/video
data are important in disaster recovery. Image/video
content can instantly provide detailed information topeople in disaster-stricken areas. Examples of information that may need to be transmitted or exchanged
after a disaster are shown in Fig. 1.
A portable media storage and transmission system
can provide such information to people working indisaster relief offices and to evacuees at evacuation
centers and in their own homes. Our media storage
and transmission system is based on the speciallydesigned Movable and Deployable ICT Resource
Unit, which we refer to as an MDRU. MDRUs will betransported immediately to a disaster area to provide
recovery of ICT services. The media storage andtransmission system must transmit information to thegreatest extent possible within the capacity restrictions posed by MDRUs. The proposed system isimplemented by the following steps.
(1)	Transport and activation of stand-alone MDRUs
to disaster areas
An MDRU with a cache server is quickly transported to a disaster area. The MDRU holds a cacheserver that runs software for the media storage andtransmission system. Layered storage consisting ofrandom-access memory, solid-state drive (SSD)*1,
and hard disk drive (HDD)*2 devices is installed in
the cache server. The MDRU forms a wireless accessnetwork, with or without wired network connections,
to reach user terminals such as laptop personal computers (PCs), smartphones, and tablet devices. People
within 500 m or so from the MDRU can view information such as text and image/video data stored in thecache server and/or upload data to the cache server.
*1	 SSD: A data storage device that uses integrated circuit assemblies
as memory to store data persistently. Compared with electromechanical disks such as HDDs, SSDs are typically more resistant tophysical shock and have lower access time and less latency.
*2 HDD: A data storage device that uses rapidly rotating disks coatedwith magnetic material. HDDs remain the dominant medium due
to advantages in price per unit of storage and recording capacity.

NTT Technical Review

Feature Articles(2) Evacuation lists
Images/video canconvey information
instantly.

handwritten information
stored as images(1) Photos and videos fromindividuals
taken by smartphones,
tablet computers, etc.
MDRU
Evacuation center

MDRU coverage area
(500-m radius)(3) Surveillance camera images
and videos
used for observing infrastructuresuch as arterial roads, airports, andharbor facilities

Image/video sharing
and viewing

Fig. 1. Information needed in disaster areas.

MDRU(equipped with cache server)
MDRU

Distribution and sharing of images/video

MDRU

MDRU

MDRUs
(equipped with distributed storage)

Transmission based on
bandwidth

UploadDesktop computer(Viewing)

MDRU
Smartphone(image/video capturing, viewing)

Fig. 2. Operation of multiple MDRUs in local disaster areas.

(2)	Operation of multiple MDRUs in local disasterareas
As many MDRUs as needed are deployed to thedisaster area. Each MDRU has interworking storage
devices that form a distributed storage system alongwith the cache server. Data uploaded to each MDRU
can be backed up to and shared among the multiple
MDRUs (Fig. 2).
(3)	Operation of multiple MDRUs connected towide area network
MDRUs will be connected to a local datacenter andwide area network. Information data can be widely
shared via the local datacenter. People in the disasterVol. 13 No. 5 May 2015

area can watch news coverage originating outside thedisaster area and share information about otherareas.
The media storage and transmission system isbased on two technologies. One is disaster resilient
layered data transmission [1], and the other is networked distributed storage [2]. The former transfers
information efficiently to work within the MDRU’slimited network bandwidth and power supply. The
latter recovers data lost by 1) network congestion or
disconnection or 2) storage failures caused by MDRU
accidental power-off or MDRU transport. Moredetails of these technologies are given below.
Feature Articles

MDRU

Layered storage

Layered data

High Small

Low resolution(2) Mapping layered code
stream to layered storage

Low
Mapping

SSD
MemoryCapacityHigh resolution

Reliability

Low Large
HDD

PL2
PL1
PL0

Priority(3) Transmission oflayered code stream

High(1) Layered
image/video coding

Fig. 3. Layered data transmission.

2. Disaster resilient layered data transmission
The proposed disaster resilient layered data transmission system offers image/video services to people
in disaster-affected areas through MDRUs. The disaster resilient image/video transmission scheme isdesigned around three technologies: (1) layered
image/video coding, (2) mapping of the layered code
stream to layered storage systems installed in the
MDRUs, and (3) transmission of layered code
streams according to network bandwidth (Fig. 3).
(1) Layered image/video coding
We utilize the JPEG 2000 standard [3] created by
the Joint Photographic Experts Group (JPEG) for
layered image/video coding. Input images are decomposed into layered data in a priority manner; that is,
JPEG 2000 bit streams are created. JPEG 2000 offers
four basic scalability dimensions in each JPEG 2000
bit stream: resolution (R), SNR (signal-to-noise ratio)quality (L), spatial location (P), and component (C).
Different scalability levels are achieved by ordering
packets within the JPEG 2000 bit stream. We assume
that text data consist of handwritten notes on a bulletin board set up in an evacuation center. The handwritten information is captured by smartphones and/or tablet PCs. We use Motion JPEG 2000 (MJ2) forthe layered video coding. It specifies the use of the
JPEG 2000 format for timed sequences of images(video). Other layered video codecs such as Scalable
Video Coding (SVC), which is a scalable extension of
H.264/MPEG-4 AVC*3, or Scalable High Efficiency
Video Coding (SHVC), a scalable extension of
H.265/HEVC*4, can also be used. We selected MJ2
because of its transmission robustness and low-complexity compared with SVC and SHVC.
(2)	Mapping layered code-stream to layered storage
The layered storage system consists of randomaccess memory, SSD, and HDD devices. The JPEG
2000 bit streams are mapped to the layered storage asshown in Fig. 3. PL0, PL1, and PL2 are priority-mapping layers and are mapped to random-access memory, SSD, and HDD, respectively. The progression
order of the JPEG 2000 bit stream is determined inadvance. Different scalability levels are achieved byordering packets and can be arbitrarily assigned toeach form of storage. If MDRU power consumption
becomes a problem, we can turn off the HDD devices,
and if additional energy saving measures are necessary, the SSD devices can be deactivated.
(3) Transmission of layered code stream
JPEG 2000 is attractive as it can truncate lower
priority bit streams from partial ones. This allows for
simple responses to changes in network bandwidthand MDRU power consumption. The truncation process consists simply of extracting the required layers
from the encoded bit stream; there is no additional*3 H.264/MPEG-4 AVC (Advanced Video Coding): A video coding
standard that was developed by the JVT (Joint Video Team) of the
ITU-T (International Telecommunications Union-Telecommunication Standardization Sector) and the ISO/IEC (International
Organization for Standardization / International ElectrotechnicalCommission) in 2003. It covers common video applications ranging from mobile services and video conferencing to IPTV (Internet protocol television), high-definition (HD) TV, and HD video.
*4 H.265/HEVC (High Efficiency Video Coding): The most recent
standardized video compression standard developed by the JCTVC (Joint Collaborative Team on Video Coding) of the ITU-T and
the ISO/IEC. It reduces the bit rate by around 50% while maintaining the same subjective video quality relative to its predecessor
H.264/ MPEG-4 AVC.

NTT Technical Review

Feature Articles

Layered storage
Layered data
Low
Priority

processing of the stream itself. The MDRU forms awireless access network around itself to reach userheld equipment. The truncation consists of extracting
the required layers based on the bandwidth between
the MDRU and the user. An example of layered transmission is shown in Fig. 3 when the priority of theresolution is selected. One usage example is that theuser can see a specific full-resolution image after
overviewing multiple thumbnail-sized images. Sending only the higher resolution components of animage specified by a user results in more efficient useof network bandwidth resources.

High

PL2
PL1
PL0

Layered LDGM
Redundant
data
Low
Mid
High

Distributed storage

3. Networked distributed storage
Here, we assume that the following problems occur
after installing MDRUs and launching ICT services:
1) network congestion or disconnection and 2) storage failures caused by MDRU accidental power-off
or MDRU transport, which can occur when MDRUs
are repositioned in a disaster area. The proposed networked distributed storage system recovers data lost
because of the above problems to the greatest extent
possible. This scheme is based on three techniques:(1)	Unequal error protection of image/video components
Layered data are protected by unequal forward
error correction (FEC) codes. For this, we use previously proposed layered low-density generator matrix(LDGM) codes [4]. The layered LDGM codes provide greater protection for image/video componentsthat have been classified as more significant thanother components. Furthermore, it is advantageous inhaving lower computation complexity and communication cost in recovering lost data than the wellknown Reed-Solomon (RS) codes.
(2)	Optimum source*5 and repair*6 packet deployment for distributed storage
Generated source and repair packets are deployed
to distributed storage (i.e., a number of storage devices), as shown in Fig. 4. To reduce the impact of astorage failure to the maximum extent, source andrepair packets are deployed uniformly to each storage
device. Furthermore, successive repair packets are
deployed to different storage devices; they are notdeployed to the same storage device to ensure thatthey are not lost. This is because if successive repair*5 Source packet: A packet consisting of layered data (JPEG 2000 bit
streams).
*6 Repair packet: A packet containing redundancy information forerror correction.

Vol. 13 No. 5 May 2015

Fig. 4. S ource and repair packet deployment for distributed
storage.

packets are lost, the error recovery probability
decreases because LDGM codes use the staircase
matrix.
(3)	Implementation compliant with next-generation
MMT standard
MPEG Media Transport (MMT) is a new media
transport standard being developed as ISO/IEC
23008-1 [5]. MMT specifies technologies for thedelivery of coded media data for multimedia services
over concatenated heterogeneous packet-based network segments including bidirectional IP (Internet
protocol) networks and unidirectional digital broadcasting networks. MMT FEC codes are also specified
in ISO/IEC 23008-10 [4]. We developed our networked distributed storage system to be compliant
with the MMT standard. Source and repair symbols
are packetized to MMT source and repair packets
according to the MMT specifications. The packets aredelivered by the MMT delivery protocol. This isadvantageous in that storage and streaming data canbe treated in a unified framework.
4. Field trial
We established an experimental environment inorder to evaluate the proposed disaster resilient
network and services based on MDRUs. We demonstrated its feasibility in a field trial on February 28,Feature Articles

Cache server(3) Connecting MDRUs and cacheserver to recover lost data
Large
MDRU

Small
MDRU

Amount of data
about 1/300
SSD
MemoryHDD(1) Removing
HDD(2) Thumbnail
viewing

Lower resolution
components

Viewing

Higher resolution
components(4) High resolution image

Fig. 5. Overview of hardware trial.

2014 at Tohoku University. A system overview of the
field trial is shown in Fig. 5. We assumed that multiple MDRUs had been deployed to a disaster area. The
cache server was set in the demonstration room. Distributed storage was installed in both a large MDRU
and a small MDRU. Input images were decomposed
into six resolution levels. For priority mapping, we
respectively assigned the three lower and three higher
resolution components to internal (SSD) and external(HDD) storage devices. We connected a user terminal
laptop PC to the cache server via a wireless local area
network. The trial proceeded as follows:(1)	The HDD that replicates disk failure wasdemounted.
(2)	Thumbnails of multiple images were shownusing the three lower resolution components
stored in the SSD.
(3)	The cache server was connected to distributed
storage units, and the three higher resolution
components were recovered.
(4)	The three higher resolution components of thespecific image specified by the user were transmitted, and the full resolution version of theimage was shown.
This trial verified that thumbnails of multiple
images could be shown even with the failure of the
HDD device. After the thumbnails were overviewed,
the full resolution version of the specific image wasshown by transmitting only its additional higher resolution components. We showed that lost data wererecovered by using the layered LDGM codes. Details
on the complexity and performance of image/videocoding and LDGM codes can be found in other

reports [1, 2].
This trial also demonstrated the usefulness of thetechnologies being developed. We plan to continue
this research in order to create innovative technologies that will enable rapid access to communication
tools under constrained circumstances such as after adisaster.
Acknowledgement
Part of the work in this article is being conductedunder the national projects, R&D on the reconfigurable communication resource unit for disasterrecovery, and R&D of “Movable ICT Units” foremergency transportation into disaster-affected areas
and multi-unit connection, both supported by the
Ministry of Internal Affairs and Communications ofJapan.
References
[1]
[2]
[3]
[4]

[5]

T. Nakachi, A. Okada, and T. Fujii, “MMT AL-FEC Codes for Networked Distributed Storage,” Proc. of IEEE ISPACS 2014, pp. 324–
329, Kuching, Sarawak, Malaysia, Dec. 2014.
T. Nakachi, A. Okada, and T. Fujii, “An MDRU Distributed Storage
System Using Layered LDGM Codes,” Proc. of ISIVC 2014, Marrakech, Morocco, Nov. 2014.
ISO/IEC 15444-1: Information technology—JPEG 2000 image coding system—Part 1: Core coding system, ISO/IEC JTC1/SC29,
2004.
ISO/IEC 23008-10: Information technology—High efficiency coding
and media delivery in heterogeneous environments—Part 10: MPEG
media transport forward error correction (FEC) codes, ISO/IEC
JTC1/SC29, 2015.
ISO/IEC 23008-1: Information technology—High efficiency coding
and media delivery in heterogeneous environments—Part 1: MPEG
media transport (MMT), ISO/IEC JTC1/SC29, 2014.

NTT Technical Review

Feature Articles

Takayuki Nakachi

Senior Research Engineer, Media Processing
Systems Research Group, NTT Network Innovation Laboratories.
He received the Ph.D. in electrical engineeringfrom Keio University, Tokyo, in 1997. Since joining NTT in 1997, he has been engaged inresearch on super-high-deﬁnition image/videocoding and communication networks. His current research interests include distributed source
coding, super resolution, and secure media processing. From 2006 to 2007, he was a visiting
scientist at Stanford University, CA, USA. He isa member of the Institute of Electronics, Information and Communication Engineers (IEICE)
and the Institute of Electrical and Electronics
Engineers (IEEE).

Sun Yong Kim

Senior Member, Strategic Business Development Division, NTT.
She received her M.S. in computer sciencefrom the University of Tokyo in 2004. She joined
NTT Network Innovation Laboratories in 2004.
Her interests are data mining, machine learning,and statistics.

Vol. 13 No. 5 May 2015

Atsushi Okada

Research Engineer, NTT Network Innovation
Laboratories.
He received the B.S. in systems engineeringfrom the University of Electro-Communications,Tokyo, in 2003, and the M.S. in interdisciplinary
information studies from the University of Tokyoin 2005. He joined NTT Network Innovation
Laboratories in 2005 and has been researching
multi-channel audio transmission systems andreliable content distribution systems.

Tatsuya Fujii

Group Leader, Media Processing Systems
Research Group, NTT Network Innovation Laboratories.
He received the B.S., M.S., and Ph.D. in electrical engineering from the University of Tokyoin 1986, 1988, and 1991, respectively. He joined
NTT in 1991. He has been researching parallel
image processing and super-high-definition
image communication networks. In 1996, he wasa visiting researcher at Washington University in
St. Louis, MO, USA. He was a director of a digital cinema development project. He is currently
studying real-time 4K video communication
system architecture and reliable content distribution systems. He is a member of IEICE, theInformation and Television Engineers (ITE) of
Japan, and IEEE.

Feature Articles: Movable and Deployable ICT Resource Unit—
Architecture for Quickly Responding to Unexpected ICT Demand

ICT Service for MDRUs
Satoshi Kotabe, Toshikazu Sakano, and Tetsuro Komukai
Abstract

In this article, we describe an Internet protocol (IP) phone service system and an evacuee management
system that were developed as information and communication technology (ICT) services for Movable
and Deployable ICT Resource Units (MDRUs) to assist in recovery after large-scale disasters. Deploying an MDRU with IP-PBX (IP-based private branch exchange) functionality to the affected areas makes
it possible to immediately provide IP phone services via Wi-Fi. The evacuee management system proposed here enables the efficient collection of evacuee data in evacuation centers.
Keywords: phone service, IP-PBX, evacuee management system

1. IP phone service for disaster relief
The proposed Internet protocol (IP) phone system
employs an extended IP-based private branchexchange (IP-PBX) system that is installed in the
Movable and Deployable information and communication technology (ICT) Resource Unit (MDRU).
The IP phone system is expected to be used for emergency communication by local governments and residents at evacuation centers when telecommunication
services are disrupted for an extended period of timeafter a large-scale disaster [1]. The features of thesystem allow quick and convenient startup of the• Connect to MDRU through wireless network (Wi-Fi
automatic configuration).
• Register user terminal information in IP-PBX(automatic registration of telephone number).
• Configure Disaster Phone software phone, enable
voice calling, and launch standard telephone
application.
• Disaster Phone application (temporary name)operates in the background and displays an iconin the status bar.

phone service.
Voice calls can be made using Wi-Fi with smartphones, tablets, or computers. Users can make voice
calls immediately simply by registering the telephone
number of the terminal they are using. Calls can bemade and received with the mobile or landline telephone number normally used. Users can download
the application to his/her smartphone from the serverin the MDRU. The IP phone application on a smartphone is shown in Fig. 1. Tapping the icon on the
Disaster Phone application automatically triggers theregistration and enables immediate voice calling. The
phone is connected to and configured by NTT’s

Voice calling is enabled
when two green icons
appear in the status bar.

Tap the icon.

Fig. 1. IP phone application for smartphones.



NTT Technical Review

Feature Articles

Disaster-use IP-PBX

Battery

Wireless LAN accesspoint (Wi-Fi AP)

Mobile terminals(Lent out/shared with people
without smartphones)
Attaché case type ICT Box

No mobile service contract
required; telephone calls canbe made if Wi-Fi is available.

The necessary devices are packed
in a portable attaché case; theminimum communication functions
can be provided immediately bytaking it to a disaster area.

Adapter for WAN
connections

LAN: local area network
WAN: wide area network

Fig. 2. Attaché case type ICT Box for IP phone system.

FLET’S HIKARI DENWA phone service router,after which calls can be made to, and received from,outside lines.
We also developed a prototype of an attaché casetype MDRU (ICT Box), in which the functions necessary for specific services are modularized to improve
portability [1]. The ICT Box, which holds the module
implementing the proposed IP phone service system,
is shown in Fig. 2. It consists of a small IP-PBX,
mobile battery, Wi-Fi access point, and a VoIP (voiceover IP) adapter, all placed within an attaché case. We
conducted an experiment and confirmed that the
18,000-mAh mobile battery enabled the portable
MDRU to operate for 5 hours, during which time 140
calls were placed. The offered service and ICT
resources are limited with this device, but its portability is excellent.
2. Evacuee management system
The evacuee management system was also developed as an ICT service essential for recovering fromlarge-scale disasters. It allows data on people affectedby the disaster to be rapidly gathered. The features
and advantages of the system are shown in Fig. 3.
The unified management of data is possible by giving each person an IC card with a unique identification (ID); this ensures seamless data handling regardVol. 13 No. 5 May 2015less of whether people are moved from evacuation
centers to temporary housing. Accurate managementof people by associating facial photographs and personal information (name, age, gender, address, etc.) is
also possible. Moreover, it offers questionnaire andstatistical analysis functions that make it possible tolearn about evacuation center conditions and to findout current requirements in real time.
When the portable IP phone system using the attaché case prototype is connected to the Internet, it ispossible to provide the collected data to the “J-anpi[2]” service operated by NTT Resonant Inc.
3. Subjective evaluation experiment
We conducted a subjective evaluation experimentof the IP phone service in cooperation with the University of Aizu during a campus festival held in October 2013. A photograph of this event is shown in
Fig. 4. About 300 men and women ranging in age
from their teens to their 70s participated. They wereasked to evaluate the service’s effectiveness on a 5level scale. The results of the subjective evaluation
are shown in Fig. 5. As shown in the figure, more than
95% of evaluators ranked the service as useful or very
useful.
We also conducted a subjective evaluation experiment of the evacuee management system. At theFeature Articles

Acquiring data on people
affected by disasters

IC CardNFC-compatible mobile
phone(Phone belonging to person affectedby the disaster, or one that has been
provided)
Facial photograph of person
affected by the disaster
Document of person affectedby the disasters(Certificate, registration card,
name card, name tag)
Questionnaire on facilities,
supplies, medical condition,etc.

Utilizing data on people
affected by disasters

NFC-compatible tablet

Evacuee card

Bundling data on people affected by disasters
with a unique ID of IC card enables total data
management of people affected by disasters,
regardless of whether they move from
evacuation centers to temporary housing.

Read unique ID.

Accurate management of people affected bydisasters and creation of information on theirwell-being by bundling facial photographs andpersonal information (name, age, etc.)

Take photo.

Take photo.
With statistical analysis:• Plans to dispatch medicalcare teams• Plans to distributesupplies

Input information.

I’m glad that person is
all right!

Send supplies to suchand-such district
immediately!

Make available tocooperatingorganizations andthe Internet.

Data entry, tabulation,
analysis, and disclosureby operators

Data input by
volunteers

ID: identification
NFC: near-field communication

Fig. 3. Features and advantages of evacuee management system.

2% 2%

0%

2%
Very useful25%

Useful69%

No opinion
Useless
Completely useless
No comment

Fig. 5. Subjective evaluation results of IP phone system.
Fig. 4. Subjective evaluation conducted at University of
Aizu.

Tohoku Section Joint Convention of the Institutes ofElectrical and Information Engineers, Japan, held
August 22–23, 2013 at the University of Aizu, a conference area was made into an evacuation center, and

assessment tests were conducted to determine how
quickly the participant information database could becreated and the collected information utilized. Around
200 of the 500 conference attendees participated in
the experiment. The functions of the evacuee management system were assessed through surveys andbriefings. The result was that more than 80% of
NTT Technical Review

Feature Articles

evaluators ranked the system as useful or very usefulduring a disaster.
4. Conclusion
We proposed an emergency IP phone service system and an evacuee management system to assist
MDRUs in recovering from a large-scale disaster.
The systems can be installed in a variety of MDRU
units that will be transported to the damaged area
after a disaster occurs. Prototype systems were developed, and subjective evaluations were performed.
The evaluation results confirmed the effectivenessand feasibility of our proposed system.
Acknowledgments

under the national projects, R&D on the reconfigurable communication resource unit for disasterrecovery and R&D of “Movable ICT Units” for emergency transportation into disaster-affected areas andmulti-unit connection, both supported by the Ministryof Internal Affairs and Communications of Japan.
The authors would like to express their appreciation
to the project members from Tohoku University andFujitsu Corporation for their collaboration.
References
[1]

[2]

S. Kotabe, T. Sakano, K. Sebayashi, and T. Komukai, “Rapidly
Deployable Phone Service to Counter Catastrophic Loss of Telecommunication Facilities,” NTT Technical Review, Vol. 12, No. 3, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
03ra1.html
Website of J-anpi, http://anpi.jp/top?lang=en

Part of the work in this article is being conducted

Satoshi Kotabe

Senior Research Engineer, Media Innovation
Laboratory, NTT Network Innovation Laboratories.
He received the B.E. and M.E. in electronicengineering from Ibaraki University in 1993 and1995, respectively. He joined NTT in 1995. His
work has focused mainly on high-speed data
communication network architectures. His current research interests include the protocols andarchitectures of disaster relief networks. He is amember of the Institute of Electronics, Information and Communication Engineers (IEICE).

Toshikazu Sakano†

Tetsuro Komukai

Senior Research Engineer, Photonic Transport
Network Innovation Laboratory, NTT Network
Innovation Laboratories.
He received the B.E. in electrical engineeringand the M.E. in electrical and communicationengineering from Tohoku University, Miyagi, in
1986 and 1988, respectively, and the Ph.D. inelectronics engineering from the University ofTokyo in 2004. He joined NTT Transmission
Systems Laboratories in 1988 and engaged in
R&D of fiber amplifiers, fiber Bragg gratings,
and optical transmission systems. He is currently
focusing on R&D of resilient ICT infrastructure
available in disaster situations. He is a Senior
Member of OSA, and a member of IEICE, IEEE,and the Japan Society of Applied Physics.

Senior Research Engineer, Supervisor, Photonic Transport Network Laboratory, NTT Network Innovation Laboratories.
He received the B.E., M.E., and Ph.D. in electronics engineering from Tohoku University,
Miyagi, in 1985, 1987, and 1998, respectively.
He joined NTT Transmission Systems Laboratories in 1987. Since joining NTT, he has been
active in several research and development(R&D) fields including optical signal processing
for high-performance computing systems, superhigh-definition imaging systems, photonic network architectures, and large-capacity opticaltransmission systems. Since the Great East Japan
Earthquake in March 2011, he has been engaged
in R&D of resilient ICT infrastructure available
in disaster situations. He received the Young
Engineer Award from IEICE in 1994 and the Best
Paper Award from the Institute of Electrical andElectronics Engineers (IEEE)’s International
Conference on Computer Design in 1990 and
1993. He is a Senior Member of IEICE and the
Optical Society of America (OSA), and a member of IEEE.
†As of January 2015, he is a director of Advanced
Telecommunications Research Institute International (ATR).

Vol. 13 No. 5 May 2015



Feature Articles: Movable and Deployable ICT Resource Unit—
Architecture for Quickly Responding to Unexpected ICT Demand

Overseas Deployment of MDRU: ITU
Project in the Philippines, and MDRU
Standardization Efforts
Hideki Nishizawa and Toshikazu Sakano
Abstract

The network facility at the San Remigio municipality on Cebu Island in the Philippines sustained
enormous damage from super typhoon Haiyan in November 2013. NTT Network Innovation Laboratories, NTT Communications Corporation, and partners initiated a feasibility study on restoring telecommunication and information and communication technology (ICT) infrastructure damaged by typhoon
Haiyan through the use of the Movable and Deployable ICT Resource Unit (MDRU), under cooperation
between the Ministry of Internal affairs and Communications of Japan, the Department of Science andTechnology of the Philippines, and ITU (International Telecommunication Union). We report on thisfeasibility study in this article. We also introduce the work being done to standardize the MDRU by NTT
Network Innovation Laboratories.
Keywords: ITU, disaster relief, overseas deployment

1. Introduction
In November 2013, NTT won a prize at the ITU(International Telecommunication Union) Telecom
World awards being held in Bangkok, Thailand in the
category of Broadband in all phases of disaster management and risk reduction for its research and development (R&D) of the Movable and Deployable
information and communication technology (ICT)
Resource Unit (MDRU) [1]. The effectiveness of the
MDRU as an emergency telecommunication platform
has since received high commendations from worldwide entities adopting disaster prevention measures,
including the nonprofit organization Philippine Central Visayas Information Sharing Network (CVISNET) Foundation, Inc.*, which has been encouraging
broad use of ICT in the Philippines.
The islands of the Philippines lie in the typhoon
corridor in the Pacific area and experience an averageof 20 typhoons per year. Typhoon-fed storms andhigh water are the most critical problems for the Philippine government and its residents. In November
2013, the Visayas region of the Philippines felt thefull force of the super typhoon Haiyan. Typhoon-fed
storm surges grew to several meters high along thesea coast and caused widespread devastation in thearea similar to that of a tsunami. To make mattersworse, the communication blackout obstructedattempts to evacuate people. About 6200 people losttheir lives in the typhoon, and the number of missing
remains at about 1800 [2].
National disasters are on the rise because of climatechange, and thus, the United Nations and the international community are continuing efforts to find ways
to reduce the risk of natural disasters, prevent the lossof lives, and reduce economic losses. In the process,the Government of Japan and the ITU are collaborating to provide assistance to restore telecommunication connectivity in one of the islands most affectedby typhoon Haiyan. On May 13, 2014, the Ministry*

The CVISNET Foundation, Inc. is an e-government project in thePhilippines funded by the Department of Science and Technology
Region 7, and a joint collaboration of the Regional Development
Council Region 7, the Government Organization for Information
Technology, and the Confederation of Scientific and Professional
Organizations.

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Feature Articles

Barangay 1
Barangay 2
SU 2

SU 1
Municipal Building
PTP 1

Cebu Islands
Philippines

PTP 2

PTP 3
BagticAU 1
BankasanSan Miguel

Fig. 1. Location of San Remigio municipality in the Philippines and depiction of wireless network in San Remigio before thetyphoon. (The network was destroyed by the typhoon.)of Internal Affairs and Communications (MIC), theDepartment of Science and Technology (DOST), and
ITU finalized a cooperation agreement for a feasibility study on restoring connectivity through the use of
the MDRU and launched the project.

nical testing as well as sustainable operation andmanagement, including the provision of training tolocal staff and improving the disaster management
planning structure in local communities for increased
disaster preparedness.

2. Summary of ITU project

3. Launching the feasibility study

The ITU project, entitled Feasibility study of restoring connectivity through the use of the Movable and
Deployable ICT Resource Unit was inaugurated in
May 2014 with the objectives of studying the effectiveness of the MDRU in providing immediate communication infrastructure and IT (information technology) facilities in the worst disaster-stricken areas
in Cebu, Philippines, and in studying the viability of
the MDRU as a communication solution in the aftermath of a disaster. San Remigio municipality on Cebu
Island was the location of the MDRU feasibility
study. The municipality consists of 27 barangays, or
districts, and has a population of about 64,000. Onsite reports of the disaster were gathered manually
because all communication networks had been
destroyed (Fig. 1). The only source of communications to the government was through a satellite phone
under the office of the Mayor.
A summary of the feasibility study is given in
Table 1, and a press release announcing that ITU,
MIC, and DOST had signed the cooperation agreement, along with a photo of the signees, is shown in
Fig. 2. The scope of this feasibility study covers tech-

After agreement of the cooperation contract wasreached, NTT and NTT Communications Corporation (NTT Com) started preparing for the feasibility
study in collaboration with local government staff
members and residents. The installation of the
MDRU, project administration, and support were carried out by NTT Network Innovation Laboratories,
NTT Com, NTT Advanced Technologies Corporation, NTT Electronics Corporation, Fujitsu Limited(from Japan), and CVISNET and Diff Sigma Tech
Inc. (from the Philippines). NTT Com, Diff Sigma,
and Kyocera Corporation respectively provided the
MDRU server unit, the MDRU wireless system, andheavy-duty smartphones. The MDRU server unit andthe MDRU wireless system used in the project are
shown in Fig. 3. They were installed in December
2014 in San Remigio Municipal Hall, and the wireless equipment was installed in a national high school(about 400 m away from the hall), where an evacuation center had been set up. Point-to-point wirelessequipment provided a communication link between
the municipal hall and the high school. The MDRU
team established a wide area Wi-Fi network byVol. 13 No. 5 May 2015



Feature Articles

Table 1. Summary of project.
Project scope

Test the feasibility of the newly developed MDRU in disaster-affected areas,
including a suitable location for installation.
Provide adequate training to local key personnel for sustainable operation andmanagement of the MDRU network.
Improve disaster management planning structure in local communities forincreased disaster preparedness.
Gain feedback from government organizations and local communities on theservices powered by the MDRU.
Provide feedback on the project to government organizations throughmonitoring and evaluation of the installed MDRU.

Project management

The project is led by ITU. The ITU Project Manager provides the overallmanagement and administration of the project in close collaboration with MIC
and DOST.
A steering committee was established immediately after the signing of thecooperation agreement.

Monitoring

ITU will monitor and evaluate the project based on the expected results andkey performance indicators.

Term

May 2014–September 2015

Fig. 2. Press release of cooperation agreement issued by
the Philippine government and photo of signees.

employing AP (access point)-AP connection between
the Wi-Fi APs at the municipal hall and those at thehigh school, and a 24-GHz FWA (fixed wirelessaccess) connection between the two buildings [3]. We
confirmed through the feasibility study that the

MDRU operated effectively in the environment in thePhilippines even though there were some differences
between Japan and the Philippines.
An example of a use case in the event of a disasteris shown in Fig. 4. In this case, the mayor first calledmunicipal employees on the phone to get information
about the disaster. Then, the municipal employees
took pictures of the disaster-affected area with asmartphone and saved them on the server in the
MDRU. This enabled the mayor to gain a visual
understanding of the disaster affected area by looking
at the pictures stored in the server. The mayor theninstructed employees at the municipal hall to provide
relief goods in the affected area, and then he reported
on the situation to the central government.
We plan to continue working to improve some
operation rules, the connectivity, and the specifications of the MDRU by conducting a feasibility studyof each use case in order to meet the needs of municipal employees and local residents.
The scope of this feasibility study included not only
technical testing but also the provision of training. A
training session on installing and running the MDRU
applications [4] in the smartphone was held for the
residents of San Remigio (Photos 1 and 2). Of 30
people who attended, more than 90% of them said
that the MDRU phone was “easy to use” or “veryeasy.” The briefing session is shown in Photo 3, in
which the essential points and the importance of the
MDRU feasibility study were discussed with theengineers in San Remigio, and the technologies usedin the MDRU project were explained. We demonstrated that the MDRU was easy to use for residents
NTT Technical Review

Feature Articles

AP4

AP relay (5 GHz)

HealthcenterFWA
AP relay(5 GHz)

00

A

AP5
AP3

Hz

AP6

FW

AP relay(5 GHz)FWA

AP relay(5 GHz)Access
2.4G

G

24

Municipal hall
Access
2.4G

(4

Staff
room

)

m

AP7

Computerroom

AP2

Evacuation area

PoliceAP1MDRU

National high school

Access 2.4G

Fig. 3. MDRU and wireless equipment installed at San Remigio Municipal Hall and at a high school.

Smartphone

Relief supplies stored at San
Remigio Municipal Hall.

(2) The mayor obtains information on
the disaster affected area via
smartphone; he gets updates from
employees and looks at images of
the area stored on a server.

(1) Pictures of disaster-affectedarea are taken with a smartphoneand stored on MDRU server.

Fig. 4. Use case of MDRU: investigating the extent of damage from the typhoon.

in San Remigio through this feasibility study. The
MDRU will need to be equipped with a power generator when a long-term power outage occurs,
although some UPSs (uninterruptible power supplies)
have already been mounted on MDRUs. We plan toVol. 13 No. 5 May 2015

confirm the feasibility and review the rules andoperation of the MDRU with local residents.

Feature Articles

Photo 3. B riefing session for engineers in San Remigio on
the essential points and importance of the MDRU
feasibility study and on the technologies used in
the MDRU project.
Photo 1. Training session for residents of San Remigio.

the MDRU in Study Group 15 by 2016 because ITUT standardization is the crucial element for promoting broad use of the MDRU throughout the world [5].
The technical report entitled Requirements on the
improvement of network resilience and recovery withmovable and deployable ICT resource units that
describes the immediate lessons learned after theGreat East Japan Earthquake are already available on
the ITU-T FG-DR&NRR website [6].
5. Future plans

Photo 2. Installing and running the MDRU applications ona smartphone.

NTT and NTT Com are working to promote broaduse of the MDRU throughout the world for disaster
relief after large-scale disasters and to expand its use
in other applications such as in prompt provision of
ICT services in developing countries lacking ICT
infrastructure.
Acknowledgments

4. Standardization
The Japanese government led the discussion on
establishing a Focus Group (FG) on disaster relief in
ITU-T (ITU-Telecommunication Standardization
Sector), and it was agreed to establish the Focus
Group on Disaster Relief Systems, Network Resilience and Recovery (FG-DR&NRR). Many Japanese
use cases including MDRU had been proposed for thedeliverables of FG-DR&NRR during two years of
discussions and standardization efforts. Since the FG
activities were finalized in June 2014, we have beenworking on finalizing an ITU-T Recommendation of

The MDRU project is a joint R&D effort between
NTT, Tohoku University, Fujitsu Limited, and NTT
Com. This R&D project is partially supported by the
Ministry of Internal Affairs and Communications ofJapan.
References
[1]

[2]

T. Sakano, S. Kotabe, and T. Komukai, “Overview of Movable and
Deployable ICT Resource Unit Architecture” NTT Technical Review,Vol. 12, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa1.html
Ministry of Land, Infrastructure, Transport and Tourism, “Overview
of Damage by Typhoon Haiyan in the Philippines” (in Japanese).

NTT Technical Review

Feature Articles

[3]

[4]

http://www.mlit.go.jp/river/shinngikai_blog/shaseishin/kasenbunkakai/shouiinkai/r-jigyouhyouka/dai04kai/siryou6.pdf
Y. Shimizu, Y. Suzuki, T. Kumagai, and K. Goto, “Wireless AccessNetwork System Using M2M Wireless Access for MDRU,” NTT
Technical Review, Vol. 12, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa2.html
S. Kotabe, T. Sakano, and T. Komukai, “ICT Service for MDRUs,”
NTT Technical Review, Vol. 12, No. 5, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
05fa5.html

Hideki Nishizawa

Senior Research Engineer, Supervisor, NTT
Network Innovation Laboratories.
He received the B.S. and M.S. in physics from
Chiba University in 1994 and 1996, respectively.
He joined NTT Network Service Systems Laboratories in 1996, where he engaged in research on
photonic switching systems. He moved to NTT
Phoenix Communications Inc. (now NTT
BizLink Inc.) in 2001, where he worked on thedevelopment of visual communication services.
He moved to NTT Research and Development
Planning Department in 2007, where he wasinvolved in planning R&D activities for future
networks. He has been with NTT Network Innovation Laboratories since 2014. He is a memberof the Institute of Electronics, Information andCommunication Engineers (IEICE).

[5]

[6]

N. Araki and H. Imanaka, “Results of ITU-T Focus Group on Disaster
Relief, Network Resilience and Recovery (FG-DR&NRR),” NTT
Technical Review, Vol. 12, No. 12, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
12gls.html
ITU-T Focus Group Technical Report, “Requirements on the
Improvement of Network Resilience and Recovery with Movable and
Deployable ICT Resource Units,” FG-DR&NRR Version 1.0, 2014.
http://www.itu.int/dms_pub/itu-t/opb/fg/T-FG-DRNRR-2014-7PDF-E.pdf

Toshikazu Sakano†

Senior Research Engineer, Supervisor, Photonic Transport Network Laboratory, NTT Network Innovation Laboratories.
He received the B.E., M.E., and Ph.D. in electronics engineering from Tohoku University,
Miyagi, in 1985, 1987, and 1998, respectively.
He joined NTT Transmission Systems Laboratories in 1987. Since joining NTT, he has been
active in several R&D fields including opticalsignal processing for high-performance computing systems, super-high-definition imaging systems, photonic network architectures, and largecapacity optical transmission systems. Since theGreat East Japan Earthquake in March 2011, hehas been engaged in R&D of resilient ICT infrastructure available in disaster situations. He
received the Young Engineer Award from IEICE
in 1994 and the Best Paper Award from the Institute of Electrical and Electronics Engineers(IEEE)’s International Conference on Computer
Design in 1990 and 1993. He is a Senior Memberof IEICE and the Optical Society of America(OSA), and a member of IEEE.
†As of January 2015, he is a director of Advanced
Telecommunications Research Institute International (ATR).

Vol. 13 No. 5 May 2015

Regular Articles

InP-based Membrane Optical Devices
for Large-scale Photonic Integrated
Circuits
Takaaki Kakitsuka, Koichi Hasebe, Takuro Fujii,
Tomonari Sato, Koji Takeda, and Shinji Matsuo
Abstract

Large-scale photonic integrated circuits for telecom and datacom applications have attracted attention
for many years. We have developed III-V based membrane optical devices employing lateral p-i-njunctions with buried heterostructures. This article introduces lateral current injection lasers andmodulators integrated on an InP substrate and membrane lasers on a SiO2/Si substrate as promisingbuilding blocks of integrated transmitters.
Keywords: semiconductor laser, modulator, photonic integrated circuit

1. Introduction
Network traffic is increasing exponentially alongwith the explosive growth of social media [1]. The
development of optical fiber networks has made it
possible to achieve high-speed, large capacity, andreliable networks. Device integration has been a key
technology in reducing power consumption in electronic and optical devices, making it possible toachieve environmentally friendly networks. Largescale electronic integration based on complementary
metal-oxide semiconductor (CMOS) technology has
contributed to the development of high-performance
processers and memories with low power consumption. We have now entered an era of photonic integration. Integrated photonic devices such as transmittersand receivers are now available thanks to the advances in fabrication technology. Photonic integrated circuits (PICs) have been developed to provide the following benefits: (1) compactness, (2) a reduction in
the number of components, (3) low power consumption, (4) low-cost fabrication, and (5) integration ofphotonics and electronics. Semiconductor platforms
consisting of III-V semiconductors* and silicon havebeen developed to meet these requirements.


Wavelength-division multiplexing (WDM) is
employed in telecom networks to transmit opticalsignals. This involves the use of integrated opticaldevices such as an electro-absorption (EA) modulator
integrated distributed feedback (DFB) laser and atunable DFB laser array on an InP substrate. However, the numbers of devices and functions have been
limited. Recently, advanced modulation formats,which use a combination of amplitude and phasemodulation, are triggering higher density integration
for core and metro networks. InP-based large-scalemonolithically integrated transmitters and receivers
consisting of more than 100 optical components havebeen reported [2]. Because the number of components is increasing, these photonic integration technologies are promising in their potential to reduce
assembly costs and footprints.
In addition, photonic networks have been expanded
to short reach applications such as in access networks
and datacom networks. Laser arrays and detector
arrays are now used in 100-Gigabit Ethernet transceivers [3]. Each discrete device operates at the speed*

III-V semiconductor: A semiconductor formed with elementsfrom both the group III and group V compounds.

NTT Technical Review

Regular Articles

Laser/Amplifier region
p-electroden-electrodeLasersp-InP

Modulators

Waveguides

n-InP
Active corei-InP
regionInsulation layer
Passive waveguide region

Modulator region
p-electroden-electrodei-InP
Passivecore region
Insulation layer

p-InP
i-InP

n-InP
Active coreregionInsulation layer

Fig. 1. Concept of PICs based on membrane optical devices.

of 10–25 Gbit/s. The trend in using photonic integration is obviously growing because of the need toreduce the cost and power consumption of networks.
In datacom applications, multi-mode VCSELs (vertical cavity surface emitting lasers) are used as lightsources for inter- or intra-board transmissions. In the
future, WDM transmitters based on integrated singlemode laser and detector arrays will be essential toincrease the transmission capacity. Silicon photonics
have been actively demonstrated for a wide range ofapplications [4, 5] and show promise in meeting theabove requirements. Although the integration of lightsources is a challenge, most of the functions of PICs
have been implemented on silicon. Therefore, further
integration of III-V and silicon photonics devices are
expected to complement each function.
Two other factors are important in order to makefurther progress: device structure and fabrication.
Most optical devices consist of laser/amplifier, modulator/photodetector, and passive waveguide regions;
we can fabricate every optical device for every target
application by combining these components. Our aim
is to develop a flexible and scalable fabrication technique implementing this concept.
In this article, we introduce membrane devices consisting of lateral p-i-n junctions as building blocks for
PICs. We employ a selective doping technique tofabricate the p-i-n junctions, as it enables flexible
device fabrication. We first clarify the advantages ofmembrane optical devices. Then we describe lateralVol. 13 No. 5 May 2015

current injection lasers and modulators fabricated on
InP substrates for telecom applications. Finally, we
discuss III-V optical devices on silicon substrates
employing novel fabrication techniques. We also
introduce lateral current injection lasers on SiO2/Si
substrates for datacom applications.
2. Concept of photonic integration
Our concept of photonic integration consists of InPbased membrane optical devices (Fig. 1). The figure
illustrates an example of an integrated transmitterconsisting of lasers, modulators, and waveguideregions. Each active region employs a lateral p-i-nstructure along the substrate. The electrodes are fabricated on the surface to apply electrical voltage along
the lateral direction. We use selective doping techniques to fabricate the p-i-n regions. Each impurity
doping region is fabricated on a non-doped epitaxial
layer that includes the active and waveguide regions.
The selective doping technique is common in CMOS
fabrication processes, as it enables mass production.
This configuration provides higher scalability andproductivity compared with conventional devices
employing vertical p-i-n structures. Generally, theoptimum doping condition is different for each active
component. In particular, non-doped regions are
essential as the passive waveguide regions in order tosuppress the optical propagation loss. Conventional
devices with vertical p-i-n junctions require a numberRegular Articles

InP-based membrane optical device layer

SiO2/Si wafer
InP device region

Silicon photonics region
Si/SiOx/SiNx

p-InP

n-InP
SiO2

SiO2

Si

Si

Fig. 2. Membrane optical devices integrated on silicon.

InP s
ubstr
ate
Activ
e cor
e laye
r
SiO2

SiO2

SiO2

Si

Si

Si

(a) Wafer bonding(b) InP etching
Si-ionZn diffusion
implantation(c) Waveguide etching

SiO2

SiO2

SiO2

Si

Si

Si

(d) Buried layer regrowth(e) Selective doping(f) Electrode formation

Fig. 3. PIC fabrication processes employing selective doping techniques.

of crystal regrowth processes to integrate optimized
components. Our approach can form impurity-doped
regions without using epitaxial regrowth processes;
in other words, the number of regrowths decreases. In
addition, assembly with electrical components is easy
because the electrodes are formed on one side.
These applications are not limited to PICs on an InP
substrate. We propose a novel process to fabricate IIIV devices on silicon. Our approach is shown in Fig. 2.
This process uses a template consisting of III-V layers bonded on a silicon substrate. The butt-joint sections, waveguides, buried heterostructures, and doping regions are formed on this template. The use oflarge silicon wafers improves the yield. In addition,
the alignment of III-V devices on the silicon substrateis possible with a level of accuracy in the submicrometer range. Therefore, III-V active devices
can be easily integrated with silicon photonic devices
including silicon-based waveguide structures. Typical fabrication procedures are shown in Fig. 3: (a) a
III-V wafer including active layers is bonded on a
SiO2/Si substrate; (b) the InP region is removed; (c)NTT Technical Review

Regular Articles

Surface grating
8

Output power (mW)

7

p-InP

6

n-InP

SI-InP

5
4

EA modulator section

50 Gbit/s

25 Gbit/s

3

DFB laser section

ER = 7.2 dB

210

20 ps/div.
0

20

40
60
Current (mA)
(a)

80

100

10 ps/div.
(b)

Fig. 4. Characteristics of membrane devices on InP: (a) directly modulated DFB laser, and (b) EA-DFB laser.

waveguides are fabricated by etching; (d) buried heterostructures are fabricated by epitaxial regrowth; (e)p- and n-doped regions are formed by Si-ion implantation and Zn thermal diffusion; and (f) electrodes
and surface gratings are formed.
The membrane devices have some advantages inboth their device characteristics and their fabrication[6]. A lateral buried heterostructure with a p-i-n junction has lower capacitance compared with verticalp-i-n structures. This feature provides high-speed
operation of lasers, modulators, and photodetectors
due to the small RC (resistor-capacitor) time constant. In addition, introduction of III-V slab layers
sandwiched by low refractive index materials
improves the power consumption because of thestrong optical confinement. This is advantageous in
reducing the power consumption of PICs for shortreach datacom applications. In the next section, we
describe the fabrication of lasers and modulators on
InP and lasers on silicon.
3. Membrane devices on InP substrate:lasers and modulators
We fabricated lateral current injection DFB lasers[7] and EA modulators on an InP substrate [8]. The
DFB lasers were fabricated using processes similar to
those in Fig. 3 except for the wafer-bonding related
processes in Fig. 3(a) and (b). The DFB laser consistsof an InGaAlAs-based 14-well active region. A λ/4shift grating is formed on the InP surface. The staticand dynamic characteristics of a laser with a length ofVol. 13 No. 5 May 2015

400 μm are shown in Fig. 4(a). The single-mode lasing was observed at room temperature. The thresholdcurrent was 14 mA. This laser achieved 25-Gbit/s
direct modulation as shown in the inset. This was thefirst demonstration of direct modulation over 25 Gbit/s
for a lateral current injection laser.
We also developed an EA-DFB laser employing
lateral p-i-n junctions. The device structure andmodulation waveform are shown in Fig. 4(b). The
modulator section consists of an 8-well InGaAlAs
active region. The EA length is 200 μm. This structure does not exhibit a quantum-confined stark effect,
which is an operating principle of conventional quantum-well EA modulators with vertical p-i-n structures. However, we theoretically confirmed a practical optical extinction ratio without sacrificing themodulation speed. The fabricated EA-DFB laser
operates at a static extinction ratio over 20 dB. In
addition, 50-Gbit/s modulation with a dynamic
extinction ratio of 7.2 dB is obtained. This is the first
demonstration of a lateral EA-DFB laser. As a result,a sufficient modulation speed for 100- and over 100Gbit/s laser arrays for telecom applications has been
demonstrated.
4. Directly modulated lateral current
injection lasers on SiO2/Si
We also developed membrane DFB lasers on SiO2/
Si [9, 10]. A schematic of the device structure and an
SEM (scanning electron microscopy) image of thecross section are shown in Fig. 5(a). The deviceRegular Articles

Surface grating
p-InP

Output power (mW)

1.0

n-InP

SiO2

0.8
0.6
0.4
0.2
0
0

Si
Active region

25−100°C

5
10
15
Current (mA)

20

(b)

200 nm
20 ps/div.

(a)

(c)

Fig. 5. ( a) Device structure, (b) current-output characteristics, and(c) 25.8-Gbit/s modulating waveform of DFB laser on SiO2/Si.

consists of a 6-well InGaAsP-active region. The laser
was fabricated according to the processes shown in
Fig. 3. Suppressing degradation of the III-V epitaxial
layer during the fabrication process is a challenging
task. Thermal stress is induced during the fabrication
because the thermal expansion coefficients are different between the InP, SiO2, and Si layers. This stresscan cause cracks in the III-V layer. Introduction of a
III-V layer that is thinner than the critical thickness
under the induced strain solved this problem. Consequently, we successfully fabricated the buried heterostructure without serious degradation by employing
the 250-nm-thick III-V layer that included the active
region.
The current-light output characteristics of the DFB
laser are shown in Fig. 5(b). The cavity length is 73
μm, and the threshold current is 0.9 mA at a temperature of 25°C. Regardless of the high thermal resistance due to the SiO2 layer, lasing operation wasobserved up to 100°C. The laser achieved 25.8-Gbit/s
direct modulation as shown in Fig. 5(c). The bias current was 3.2 mA. The energy cost of the data transmission was 171 fJ/bit, which is the smallest value of
all DFB lasers. We also achieved 40-Gbit/s directmodulation by employing another structure. These
results show the feasibility of low-power consumption operation of membrane lasers on SiO2/Si.



5. Summary
We have presented InP-based membrane opticaldevices for large-scale PICs for network applications.
These devices achieve practical performance as wellas simple and scalable fabrication processes by meansof selective doping techniques. We successfully demonstrated DFB lasers and EA-DFB lasers fabricatedon InP, and DFB lasers fabricated on SiO2/Si. All ofthese devices achieved modulation characteristics
applicable to 100-Gbit/s or higher transmitters. In
particular, the directly modulated lasers on SiO2/Si
have the smallest energy cost of all DFB lasers: 171
fJ/bit. We believe these achievements pave the way
for further development of large-scale PICs on various platforms including InP and silicon for a wide
range of network applications.
References
[1]

[2]
[3]
[4]

Cisco, “Cisco Global Cloud Index: Forecast and Methodology
2013–2018 White Paper,”http://www.cisco.com/c/en/us/solutions/collateral/service-provider/global-cloud-index-gci/Cloud_Index_White_Paper.html
V. Lal et al., “Terabit Photonic Integrated Circuits in InP,” Integrated
Photonics Research, Silicon and Nanophotonics, IW5A, Rio Grande,
Puerto Rico USA, Jul. 2013.
IEEE P802.3ba 40Gb/s and 100Gb/s Ethernet Task Force,
http://grouper.ieee.org/groups/802/3/ba/index.html
Y. Urino, Y. Noguchi, M. Noguchi, M. Imai, M. Yamagishi, S. Saitou,
N. Hirayama, M. Takahashi, H. Takahashi, E. Saito, M. Okano, T.
Shimizu, N. Hatori, M. Ishizaka, T. Yamamoto, T. Baba, T. Akagawa,
S. Akiyama, T. Usuki, D. Okamoto, M. Miura, J. Fujikata, D. Shimura,

NTT Technical Review

Regular Articles

[5]

[6]

H. Okayama, H. Yaegashi, T. Tsuchizawa, K. Yamada, M. Mori, T.
Horikawa, T. Nakamura, and Y. Arakawa, “Demonstration of 12.5Gbps Optical Interconnects Integrated with Lasers, Optical Splitters,
Optical Modulators and Photodetectors on a Single Silicon Substrate,” Optics Express, Vol. 20, No. 26, pp. B256–B263, 2012.
K. Yamada, T. Tsuchizawa, H. Nishi, R. Kou, T. Hiraki, K. Takeda, H.
Fukuda, M. Usui, K. Okazaki, Y. Ishikawa, K. Wada, and T. Yamamoto, “Silicon-germanium-silica Monolithic Photonic Integration
Platform for Telecommunications Device Applications,” NTT Technical Review, Vol. 12, No. 5, May 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
05ra1.html
T. Okamoto, N. Nunoya, Y. Onodera, T. Yamazaki, S. Tamura, and S.
Arai, “Optically Pumped Membrane BH-DFB Lasers for Low-threshold and Single-mode Operation,” IEEE J. Sel. Top. Quantum Electron., Vol. 9, No. 5, pp. 1361–1366, Sept./Oct. 2003.

K. Hasebe, T. Sato, K. Takeda, T. Fujii, T. Kakitsuka, and S. Matsuo,“Error-free 25-Gbit/s Direct Modulation of Lateral-current-injection
DFB Laser,” 2014 Conference on Lasers and Electro-Optics (CLEO),
STh1G, San Jose, USA, Jun. 2014.
[8] K. Hasebe, T. Sato, K. Takeda, T. Fujii, T. Kakitsuka, and S. Matsuo,“High-speed Modulation of Lateral-pin-diode-structure Electroabsorption Modulator Integrated with DFB Laser,” J. of Lightwave
Technol., Vol. 33, No. 6, pp. 1235–1240, Mar. 2015.
[9] S. Matsuo, T. Fujii, K. Hasebe, K. Takeda, T. Sato, and T. Kakitsuka,“Directly Modulated Buried Heterostructure DFB Laser on SiO2/Si
Substrate Fabricated by Regrowth of InP Using Bonded Active
Layer,” Optics Express, Vol. 22, No. 10, pp. 12139–12147, 2014.
[10] S. Matsuo, T. Fujii, K. Hasebe, K. Takeda, T. Sato, and T. Kakitsuka,“Directly Modulated DFB Laser on SiO2/Si Substrate for Datacenter
Networks,” J. Lightwave Technol., Vol. 33, No. 6, pp. 1217–1222,
Mar. 2015.

Takaaki Kakitsuka

Tomonari Sato

Senior Research Engineer, Materials andDevices Laboratory of NTT Device Technology
Laboratories and NTT Nanophotonics Center.
He received the B.S. and M.S. in physics in1994 and 1996 and the Dr. Eng. in 2012 from
Kyushu University, Fukuoka. In 1996, he joined
NTT Opto-electronics Laboratories. He has been
engaged in research on semiconductor lasers andoptical functional devices. From 2009 to 2011,
he was a member of the research and development planning department. He is now with NTT
Device Technology Laboratories. He is a member of the Institute of Electronics, Information
and Communication Engineers (IEICE), theInstitute of Electrical and Electronics Engineers(IEEE) Photonics Society, Japan Society ofApplied Physics (JSAP), and the Physical Society of Japan.

Koichi Hasebe

Researcher, Materials and Devices Laboratoryof NTT Device Technology Laboratories and
NTT Nanophotonics Center.
He received the M.E. and Ph.D. in electronics
and applied physics from Tokyo Institute ofTechnology in 2005 and 2008, respectively. He
received a research fellowship for young scientists from the Japan Society for the Promotion of
Science for the years 2006 to 2009. In 2008, he
was a Postdoctoral Fellow and a Visiting
Researcher at Tokyo Institute of Technology andthe University of California, Berkeley, USA.
Since 2009, he has been with NTT Photonics
Laboratories. His current research interests
include next-generation access systems, InP
photonic functional devices, and nano-microcavity semiconductor lasers. He is a member of
IEICE and the Optical Society of America.

Takuro Fujii

Researcher, Materials and Devices Laboratoryof NTT Device Technology Laboratories and
NTT Nanophotonics Center.
He received the B.E. and M.E. in engineeringfrom Keio University, Kanagawa, in 2010 and2012, respectively. In 2012, he joined NTT Photonics Laboratories. He has been engaged inresearch on metalorganic vapor phase epitaxy(MOVPE) growth of III-V semiconductors anddevelopment of III-V semiconductor lasers on Si
for photonic integrated circuits. He is a memberof JSAP.

Vol. 13 No. 5 May 2015

[7]

Manager, IT Innovation Department, NTT
EAST Corporation.
He received the B.E., M.E., and Ph.D. in engineering from University of Tsukuba, Ibaraki, in
2001, 2003, and 2009, respectively. In 2003, hejoined NTT Photonics Laboratories. He has been
engaged in research on the MOVPE growth of
III-V semiconductors, and the development ofsemiconductor lasers for sensor applications andphotonic crystal lasers. He is a member of JSAP.
In July 2014, he moved from NTT Nanophotonics Center to NTT EAST.

Koji Takeda

Researcher, Materials and Devices Laboratoryof NTT Device Technology Laboratories and
NTT Nanophotonics Center.
He received the B.S., M.S., and Ph.D. in electronics engineering from the University of Tokyoin 2005, 2007, and 2010, respectively. From 2008
to 2010, he received a research fellowship foryoung scientists from the Japan Society for the
Promotion of Science. He joined NTT Photonics
Laboratories in 2010. His current research interests include ultralow-power optical interconnects, InP photonic integrated circuits, and photonic crystal lasers. He received the Best Student
Paper Award from IEEE Photonics Society in
2009, and the Outstanding Student Presentation
Award from JSAP in 2010. He is a member of theIEEE Photonics Society, JSAP, and IEICE.

Shinji Matsuo

Senior Distinguished Researcher, Materials
and Devices Laboratory of NTT Device Technology Laboratories and NTT Nanophotonics Center.
He received the B.E. and M.E. in electricalengineering from Hiroshima University in 1986
and 1988, and the Ph.D. in electronics andapplied physics from Tokyo Institute of Technology in 2008. In 1988, he joined NTT Opto-electronics Laboratories, where he was engaged inresearch on photonic functional devices using
MQW (multiple quantum well)-pin modulators
and VCSELs. In 1997, he researched optical
networks using WDM technologies at NTT Network Innovation Laboratories. Since 2000, he
has been researching high-speed tunable opticalfilters and lasers for photonic packet switching at
NTT Photonics Laboratories. He is a member of
the IEEE Photonics Society, JSAP, and IEICE.

Global Standardization Activities

W3C TPAC 2014 Report and HTML5
Recommendation
Shigeru Fujimura, Tomohiro Yamada, Kiyoshi Tanaka,
Taichi Kawabata, Masayuki Ihara, Kensaku Komatsu,
and Akihito Akutsu
Abstract

The W3C (World Wide Web Consortium) Technical Plenary / Advisory Committee Meetings Week
(TPAC) was held from October 27 to 31, 2014, in Silicon Valley in the USA. The year 2014 was not only
the 25th anniversary of the creation of the web but also the 20th anniversary of the foundation of W3C.
On October 28, the W3C published a formal Recommendation of HTML5 (HyperText Markup Language, fifth revision) during TPAC in this anniversary year. In this article, we report on W3C TPAC 2014
and the HTML5 Recommendation.
Keywords: W3C, TPAC, HTML5

1. Introduction
The World Wide Web Consortium (W3C), foundedby Sir Tim Berners-Lee, is a nonprofit standardization community that develops web standards. The
number of member companies and organizations was
402 as of December 2014; NTT has been a W3C
member since December 1995. The W3C develops
well-known standards such as those for HTML(HyperText Markup Language) and CSS (Cascading
Style Sheets), and its published standards are open
and freely available to the public. One of the recent
hot topics in W3C is the standardization of several
JavaScript application programming interfaces(APIs), which are implemented in web browsers toenhance the power of web applications.
One of the characteristics of the standardization
process in the W3C (Fig. 1) is that it is tightly coupledwith the implementation. For example, the call for the
implementation to browser vendors and the preparation of test suites are mandatory at the stage of the
Candidate Recommendation, so feedback on ambiguous points and on problems with specifications isgiven at this stage. As a result, in many cases, W3C
standards are already available and in wide use in the

web when they reach the W3C Recommendation
stage.

W3C Recommendation (REC)

Proposed Recommendation (PR)*3

Candidate Recommendation (CR)*2

Last Call Working Draft (LC)*1

Working Draft (WD)
*1 LC will be unified with CR for faster standardization.
*2 Call for implementation is announced at this stage.
*3 If the specification has any problems, the status isrolled back to the previous stage.

Fig. 1. Standardization process of W3C.

NTT Technical Review

Global Standardization Activities

2. W3C TPAC 2014 report
The Technical Plenary / Advisory Committee
Meetings Week (TPAC) is the W3C’s annual general
meeting held around November every year. Face-toface meetings are held for not only the Working
Groups (WGs) but also the Advisory Committee(AC), which consists of representatives of member
organizations and mainly discusses the management
policies of W3C. A large number of people attended
TPAC 2014 because 2014 was the anniversary of thecreation of the web and W3C.
The schedule of TPAC 2014, which lasted fivedays, was consistent with past TPAC events in that thefirst and last two days were reserved for WG and AC
discussions. On October 29, the third and middle dayof TPAC, breakout sessions were held from morning
to afternoon (Photo 1). The presenters were selectedfrom TPAC participants, and they managed and moderated discussions on issues that would be importantin W3C in the near future, so there were active
exchanges of opinions in many sessions. On the sameday, a plenary anniversary symposium, titled The
Future of the Web, was held from afternoon to early
evening. In this section, we report on some items ofinterest from TPAC 2014 that are related to NTT.
2.1 Advisory Board
The Advisory Board (AB) is an organization thatprovides ongoing guidance to the W3C on issues ofstrategy, management, legal matters, and the standardization process. In July 2014, Mr. Jay (Junichi)
Kishigami, a senior advisor at NTT, became one of
the nine members of the AB and the second Japanese
member. He attended the face-to-face AB meeting at
TPAC 2014 and actively discussed the future of the
web and W3C.
2.2 Web and TV IG
Standardization activities focusing on particularindustry fields are also carried out by W3C, and thebroadcasting field is one of them. One of the representative services that integrates the web and broadcasting is smart TV (television). The Web and TV
Interest Group (IG) that comprises telecommunications carriers, broadcasting organizations, manufacturers, and browser vendors discusses requirements
and use cases for the future smart TV [1]. NTT has
been actively participating in the Web and TV IG
since its establishment and is particularly interested
in the development of IPTV (Internet protocol TV).
The Web and TV IG also serves as a forum for introVol. 13 No. 5 May 2015

Photo 1. Notices of breakout sessions.

ducing methods for integrating the web and broadcasting such as Hybridcast, which was developed inJapan, and HbbTV, which is mainly used in Europe,and for sharing problems among IG members. At
TPAC 2014, NHK of Japan introduced Hybridcast2.0,
which covers the exact synchronization of time
between broadcasting and IP communications.
2.3 NTT Communications activity for the WoT
NTT Communications has been paying attention to
and working on the new technology called the Web ofThings (WoT), which enhances the potential of theweb. The concept of WoT is to realize various newuse cases by connecting people and devices, or devices and devices.
One example of the WoT is Chromecast, a smallsized media-streaming device developed by Google
Inc. that has been available in Japan since May 2014.
This device can seamlessly connect people anddevices via a web browser. For example, a movie
played in a smartphone can be easily transferred to alarge screen TV in a living room. Another example is
the AirPlay API by Apple Inc., which realizes thesame feature using the web browser in the iPhone.
Although in the present circumstances, these technologies were developed independently by individualcompanies, a discussion about combining them as the
Presentation API [2] has begun in the Second Screen
Presentation Community Group (CG) in the W3C,
and this API is expected to become a formal Recommendation in the future.
Nevertheless, the main scope of this API focuses
only on integration with TVs, and interactive useGlobal Standardization Activities

cases with other devices such as cameras are nottaken into account. Therefore, NTT Communications
proposed extending the API target devices with Sony
Corporation and Toshiba Corporation in the breakout
session (Photo 2). The room for this session was so
crowded that some attendees had to stand, and thediscussion on our proposal was quite active. As aresult, we achieved a formal request to discuss our
proposal in the Second Screen Presentation CG.
2.4 The Future of the Web symposium
At this anniversary symposium, executives of the
W3C and many esteemed guests gave speeches onpast successes and future expectations of the web.
The speakers included Sir Tim Berners-Lee, W3C
Director; Mr. Jeffrey Jaffe, W3C Chief Executive
Officer; Mr. Vinton Cerf, one of the inventors of the
TCP/IP*1 protocol; and Ms. Jessica Rosenworcel, oneof the commissioners of the U.S. Federal Communications Commission. The symposium was a great
success, and the hall was full of participants (Photo 3).
3. HTML5 Recommendation
3.1 Overview of HTML5 Recommendation
On October 28, during TPAC 2014, the formal
HTML5 Recommendation was published by the
W3C. The day before its publication, a press event
was held at the Computer History Museum in Mountain View in Silicon Valley. Many W3C members
gave testimonials on HTML5 to the W3C, as did Mr.
Katsuhiko Kawazoe, Vice President of NTT Service
Evolution Laboratories [3].
When discussing HTML5, we need to clarify
whether we are speaking about the narrowly definedor broadly defined HTML5 (Fig. 2). The narrowly
defined version simply includes specifications ofHTML tags, whereas the broadly defined one includes

Photo 2. Presentation in a breakout session.

*1	 Transmission Control Protocol/Internet Protocol

Photo 3. Future of the Web symposium.



NTT Technical Review

Global Standardization Activities

Broadly defined
Narrowly defined
Enhanced HTML tags

CSS3

Video/Audio tag(play without plugins)

Socket communication(WebSocket)

Programmatic access to
2D images (canvas)

Background processing for
JavaScript (Web Workers)
Access to device hardware(Device APIs)
Access to local files(File API)

Fig. 2. Narrowly defined and broadly defined HTML5.

various features that are achieved with CSS andJavaScript APIs. This Recommendation is for the narrowly defined HTML5, and it does not include CSS
and JavaScript API related specifications that are still
under development. This Recommendation was published to match the timing of this anniversary year.
This formal HTML5 Recommendation does notseem likely to generate any sudden changes in theweb, as HTML5 is already widespread and widelyused in many websites. For example, many readers
have probably viewed HTML5 video, which is a
specification for playing movies without browser
plug-in software.
3.2 C
 SS (ruby, text decoration, and vertical
writing mode)
CSS is a style sheet language used to describe thelooks and formatting of structured documents written
in a markup language such as HTML5. The CSS WG
is one of the largest WGs in the W3C and maintains
more than 50 specifications now. NTT is involved
with several specifications such as those for the vertical writing mode, ruby*2, and text decoration. These
specifications are very important for the Japanesewriting systems and Japanese e-Books.
CSS specifications are often quite complicated but
intriguing, and they are standardized in the samemanner as HTML5, as shown in Fig. 1. As statedabove, ruby text is especially important for the Japanese writing systems, and it involves both the structure and appearance of text. CSS Ruby has beendeveloped jointly with HTML5 WG, as HTML5 ruby*2 Ruby is small-sized annotated text that appears just above or next
to the main text.

Vol. 13 No. 5 May 2015

tags specify the text structure, and CSS ruby specifies
how ruby text is displayed.
As mentioned in the previous subsection, HTML5
was formally published as a Recommendation, and it
includes a specification for ruby-related tags. However, CSS ruby is still under development, and ourefforts will continue until it reaches the stage of W3C
Recommendation.
4. Other NTT activities related to W3C
4.1 Digital signage
The preparation-level discussion on digital signage
has been continuing in the Web-based Signage Business Group (BG). In June 2012, the W3C Workshop
on Web-based Signage was held at Makuhari Messe,
Chiba, Japan. This was the same site as that for Digital Signage Japan 2012, a joint event with Interop
2012. NTT was the host company of this workshop,
and the main topic was use cases of digital signage.
In November 2012, a face-to-face meeting of the
Web-based Signage BG was held at TPAC 2012,
which included discussions on use cases and requirements and also featured joint sessions with the MMI(Multi-Modal Interaction) WG and DAP (DeviceAPIs) WG.
The topic of most interest in the Web-based Signage BG is currently the definition of profiles of the
Web-based Signage Player, and seven profile specifications (Core, Basic Media, Storage, Basic Reporting, Interactive Menu, Emergency Information, andScheduling) are still being examined. Staff membersof NTT Service Evolution Laboratories are helping
with the Emergency Information profile definitionand have proposed the requirements for utilizingGlobal Standardization Activities

digital signage when a disaster occurs. Specifically,
we have introduced a mechanism to deliver necessary
information to a user device by connecting it to signage through a public wireless LAN (local area network) and a mechanism for administrators to update
the content of signage from mobile devices even if
users have lost their Internet connection during adisaster.
4.2 Speech recognition for web browsers
In September 2014, NTT announced the development of speech recognition technologies that can beused on multiple HTML5 browsers without plug-in
software. In this development, we utilized the latest
knowledge on W3C standardization trends and adopted a combination of JavaScript APIs in which thestandardization process is progressing on track. Thisis a characteristic example of W3C standards, inwhich a specification is implemented in multiple
browsers even if its Recommendation has not beenformally announced.

already started. That is, technical specifications that
improve the capabilities of web applications to thesame level as applications running on the OS (operating system), and technical specifications that were
excluded in the HTML5 Recommendation are being
discussed for the next version, HTML5.1. In the current plan, a Recommendation for HTML5.1 will becompleted in the fourth quarter of 2016. In addition,
discussions for HTML.next (or HTML6) have also
begun.
TPAC 2015 will be held from October 26 to 30,
2015, in Sapporo, Japan, and the requirements for
HTML5.1 will be one of the main topics discussed.
Upon conclusion of TPAC 2015, the Internet Engineering Task Force (IETF) meeting will be held for aweek in Yokohama, Japan, and thus, a discussion oncooperation with the IETF will also be a key topic at
TPAC 2015.
References[1]

5. Future prospects
The HTML5 Recommendation is a very importantmilestone not only for W3C but also for the information and communications technology field in general.
Further discussions on the next milestone have



[2]
[3]

K. Tanaka, “Standardization Trends Relating to Smart TV,” NTT
Technical Review, Vol. 12, No. 6, Jun. 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
06gls.html
Website of W3C, Presentation API,
http://www.w3.org/2014/secondscreen/presentation-api/20140721/
W3C press release, “Open Web Platform Milestone Achieved with
HTML5 Recommendation,” October 28, 2014.
http://www.w3.org/2014/10/html5-rec.html.en

NTT Technical Review

Global Standardization Activities

Shigeru Fujimura

Masayuki Ihara

Research Engineer, Natural Communication
Project, NTT Service Evolution Laboratories.
He received the M.S. in information scienceand technology from the University of Tokyo in2005 and joined NTT the same year. Since then,he has been engaged in research on web mining
and web engineering, especially on effective
implementation methods for web applications.
He is a member of the W3C Web and TV IG.

Senior Research Engineer, Supervisor, Proactive Navigation Project, NTT Service Evolution
Laboratories.
He received the M.E. and Ph.D. from Tokyo
Institute of Technology in 1994 and 2010,
respectively. He worked at the New Media Innovation Centre and at the University of British
Columbia, both in Vancouver, Canada, from2002 to 2003. His research interests include
value based design, cognition of human values
and preferences, and human-computer interaction. He is a member of ACM, IPSJ, and IEICE.

Tomohiro Yamada

Kensaku Komatsu

Senior Research Engineer, Supervisor, Networked Robot and Gadget Project, NTT Service
Evolution Laboratories.
He received the M.S. in electronics engineering from Niigata University in 1992 and theMBA from the University of Birmingham, UK,
in 2007. He joined NTT in 1992, where he has
been engaged in research on content distribution
systems and technologies to support home appliances. He is the W3C Advisory Committee Representative (ACRep) of NTT and also a memberof the Association for Computing Machinery(ACM), the Institute of Electrical and Electronics
Engineers (IEEE), and the Information Processing Society of Japan (IPSJ).

Web Application Evangelist / Senior Manager,
Dept. of Technology Development, NTT Communications Corporation.
He received the B.E. and M.E. from Yokohama
National University, Kanagawa, in 1995 and1997, respectively. He joined NTT in 1997 and iscurrently working at NTT Communications as a
Research Engineer. His current interest is cutting-edge web technology such as HTML5,
WebSocket, and WebRTC.

Akihito Akutsu

Kiyoshi Tanaka

Senior Research Engineer, Supervisor, Natural
Communication Project, NTT Service Evolution
Laboratories.
He received the B.E., M.E., and Ph.D. in communication engineering from Osaka University
in 1992, 1994, and 2005, respectively. He joined
NTT in 1994 and since then has been engaged inresearch on video-on-demand systems and metadata-related interactive video systems and services, especially those related to IPTV systems
and services. His current interests include standardization of IPTV, digital signage, and multimedia broadcasting for mobile devices. He
joined the standardization efforts of ARIB (Association of Radio Industries and Businesses) STDB38 (v2.1, 2.2, and 2.3), STD-B45 (v2.0), andTR-B33 as an editor. He has also contributed to
ITU-T’s international standardization efforts,
mainly in ITU-T SG (Study Group) 16 and IPTVGSI. He is a member of the W3C Web and TV
IG, IEICE, and the Human Interface Society inJapan.

Executive Research Engineer, Natural Communication Project, NTT Service Evolution
Laboratories.
He received the M.S. in engineering from
Chiba University in 1990 and the Ph.D. in naturalscience & technology from Kanazawa University
in 2001. He joined NTT in 1990 and began
researching video indexing technology based onimage/video processing, and man-machine interface architecture design. More recently, heworked on an R&D project involving broadband
and broadcast services. In October 2013, he wasappointed Executive Producer of 4K/8K HEVC(High Efficiency Video Coding) at NTT MediaIntelligence Laboratories. He is a member of
IEICE.

Taichi Kawabata

Senior Research Engineer, Ubiquitous Software Group, Ubiquitous Service Systems Laboratory, NTT Network Innovation Laboratories.
He received the M.S. in computer science fromthe University of Tokyo in 1997 and joined NTT
the same year. He has mainly been researching
the use of personal data on network systems. He
has also worked on standardization activities
involving character and text encoding and related
standards in ISO (International Organization forStandardization), IEC (International Electrotechnical Commission), and W3C standardization
organizations.

Vol. 13 No. 5 May 2015



New NTT Colleagues––We welcome our newcomers to the NTT Group
This is a corner of the NTT Technical Review where we introduce our new affiliate companies.

e-shelter
3rd largest datacenter operator in Europe; established in 2000, headquartered in Luxembourg
Founded in 2000, e-shelter designs, builds, and operates high-availability datacenters, whose infrastructure
guarantees the highest standards of physical security and operational reliability. The company operates over
90,000 square meters of datacenter space in four major cities in Germany, as well as in Zurich, Switzerland andVienna, Austria. One of its main facilities, Campus Frankfurt 1, is Europe’s largest datacenter, with some 60,000
square meters of datacenter space. The complex comprises five free-standing buildings constructed specificallyas datacenters (Photo 1). In March 2015, NTT Communications Corporation, the international communications
and ICT (information and communication technology) solutions provider, jointly announced with e-shelter and
ABRY Partners, a private equity investment firm, that NTT Communications would acquire 86.7% of e-shelter’s
issued shares. This acquisition will vault the NTT Communications Group into the No. 3 position for datacenter
space in Europe. For further information about e-shelter, please visit https://www.e-shelter.de/en

Photo 1. Campus Frankfurt 1.



NTT Technical Review

New NTT Colleagues

Contacts:
Public Relations Department
NTT Communications Corporation
http://www.ntt.com/aboutus_e/news/data/20150303.html

Vol. 13 No. 5 May 2015



External Awards
2014 IEICE Communications Society OCS Young Researchers Award
Winner: Masaki Wada, NTT Access Network Service Systems
Laboratories
Date: December 11, 2014
Organization: Institute of Electronics, Information and Communication Engineers (IEICE)-Technical Committee on Optical Communication Systems (OCS)

For “Flexible Ecologies and Incongruent Locations.”
This study contributes to the studies of systems to support realtime collaborative activities by presenting some form of embodiment. It develops the analysis of fractured ecologies and fragmented
interaction.
Published as: P. Luff, N. Yamashita, H. Kuzuoka, and C. Heath,“Flexible Ecologies and Incongruent Locations,” Proc. of CHI 2015,
Seoul, Korea, Apr. 2015.

For “A Study on Mode-dependent Gain Control of 2-LP-mode
EDFA within the C- and L-band.”Published as: M. Wada, T. Sakamoto, T. Mori, T. Yamamoto, N.
Hanzawa, and F. Yamamoto, “Modal Gain Controllable 2-LP-mode
Fiber Amplifier Using PLC Type Coupler and Long-period Grating,”
The Journal of Lightwave Technology, Vol. 32, No. 24, pp. 4694–
4700, Dec. 2014.

Interaction 2015 Best Interactive Presentation Award
Winner: Masanori Yokoyama, Motohiro Makiguchi, and Daichi
Namikawa, NTT Service Evolution Laboratories; Yuji Takano andSatoshi Nakashima, NTT Communication Science Laboratories;
Taiga Yoshida, NTT Media Intelligence Laboratories
Date: March 5, 2015
Organization: Information Processing Society of Japan (IPSJ)

2014 IEICE Communications Society OFT Young Researchers Award
Winner: Takayoshi Mori, NTT Access Network Service Systems
Laboratories
Date: February 19, 2015
Organization: IEICE-Technical Committee of Optical Fiber Technologies (OFT)For “Animal Cloud: Crowdsourcing System on the Basis of Animal Cognitions.”
We propose “Animal Cloud,” which is a micro-task crowdsourcing
system based on animal cognition. The required conditions of Animal
Cloud are as follows: necessity of learning the task, supplement of thetask accuracy rate, and securement of the right of choice as to whether the animals do the task or not. As the first step, we implemented animage recognition system based on a rat’s perceptional or cognitive
ability as an example of an application that fulfills the required conditions. We conducted the behavioral experiment and simulation toevaluate the feasibility of the system. The results suggested that thesystem required 50 rats that would learn the micro-task for about 15
days.
Published as: M. Yokoyama, Y. Takano, M. Makiguchi, S. Nakashima, T. Yoshida, and D. Namikawa, “Animal Cloud: Crowdsourcing
System on the Basis of Animal Cognitions,” Proc. of Interaction 2015
(the 19th IPSJ Symposium), Tokyo, Japan, Mar. 2015.

For “Design of Low DMD Few-mode Fibers Supporting Large
Number of Modes for Mode-division-multiplexed Transmission.”
Published as: T. Mori, T. Sakamoto, M. Wada, T. Yamamoto, and F.
Yamamoto, “Design of Low DMD Few-mode Fibers Supporting
Large Number of Modes for Mode-division-multiplexed Transmission,” Proc. of OFT 2014, Kushiro City, Hokkaido, Japan, Aug.
2014.
SIGCHI Best of CHI Honorable Mention Award
Winner: Ge Gao, Naomi Yamashita, Ari Hautasaari, NTT Communication Science Laboratories; Susan Fussell, Cornell University
Date: March 3, 2015
Organization: The Association for Computing Machinery (ACM)the Special Interest Group on Computer–Human Interaction (SIGCHI)
For “Improving Multilingual Collaboration by Displaying How
Non-native Speakers Use Automated Transcripts and Bilingual Dictionaries.”
We examine the value of signaling grounding problems to native
speakers by displaying how non-native speakers use automated transcripts and bilingual dictionaries. Our findings suggest ways toimprove collaboration systems.
Published as: G. Gao, N. Yamashita, A. Hautasaari, and S. Fussell,“Improving Multilingual Collaboration by Displaying How Nonnative Speakers Use Automated Transcripts and Bilingual Dictionaries,” Proc. of CHI 2015, Seoul, Korea, Apr. 2015.
SIGCHI Best of CHI Honorable Mention Award
Winner: Paul Luff, King’s College; Naomi Yamashita, NTT Communication Science Laboratories; Hideaki Kuzuoka, University ofTsukuba; Christian Heath, King’s College
Date: March 3, 2015
Organization: ACM-SIGCHI

Young Scientist Oral Presentation Award
Winner: Takahiro Inagaki, NTT Basic Research Laboratories
Date: March 11, 2015
Organization: The Japan Society of Applied Physics (JSAP)
For “Low-voltage Optical Phase Modulation by Electric-fieldinduced Phase Transition of KTN Crystal.”
Published as: T. Inagaki, T. Imai, J. Miyazu, H. Takesue, and J.
Kobayashi “Low-voltage Optical Phase Modulation by Electricfield-induced Phase Transition of KTN Crystal,” Proc. of the 75th
TSAP Autumn Meeting, Sapporo, Hokkaido, Japan, Sept. 2014.
2014 IEICE Communications Society OFT Young Researchers Award
Winner: Nobutomo Hanzawa, NTT Access Network Service Systems Laboratories
Date: March 11, 2015
Organization: IEICE-OFT
For “A Study on Mode Dependent Loss of Rayleigh Scattering.”
Published as: N. Hanzawa, K. Tsujikawa, S. Nozoe, L. Ma, and F.
Yamamoto, “A Study on Mode Dependent Loss of Rayleigh Scattering,” Proc. of the 2014 IEICE General Conference, Niigata City,
Niigata, Japan, Mar. 2014.

NTT Technical Review

Specially Selected Paper
Winner: Ryohei Banno, Susumu Takeuchi, Michiharu Takemoto,Tetsuo Kawano, NTT Network Innovation Laboratories; Takashi
Kambayashi, NTT Science and Core Laboratory Group; Masato
Matsuo, NTT Network Innovation Laboratories
Date: March 15, 2015
Organization: IPSJ

For “Designing Overlay Networks for Handling Exhaust Data in aDistributed Topic-based Pub/Sub Architecture.”
Published as: R. Banno, S. Takeuchi, M. Takemoto, T. Kawano, T.
Kambayashi, and M. Matsuo, “Designing Overlay Networks for
Handling Exhaust Data in a Distributed Topic-based Pub/Sub Architecture,” Journal of Information Processing, Vol. 23, No. 2, pp. 105–
116, Mar. 2015.

Papers Published in Technical Journals andConference Proceedings
Underdetermined Blind Separation and Tracking of Moving Sources Based on DOA-HMM
T. Higuchi, N. Takamune, T. Nakamura, and H. Kameoka
Proc. of 2014 IEEE International Conference on Acoustics,
Speech, and Signal Processing (ICASSP 2014), pp. 3215–3219, Florence, Italy, May 2014.
This paper deals with the problem of the underdetermined blindseparation and tracking of moving sources. In practical situations,sound sources such as human speakers can move freely, so blindseparation algorithms must be designed to track the temporal changes of the impulse responses. We propose solving this problem throughthe posterior inference of the parameters in a generative model of anobserved multichannel signal, formulated under the assumption of
the sparsity of time-frequency components of speech and the continuity of speakers’ movements.

Aging and Availability of Binocular Disparity and Pictorial
Depth Cues in 3D-graphics Contents
K. Kihara, H. Fujisaki, S. Ohtsuka, M. Miyao, J. Shimamura, H.
Arai, and Y. Taniguchi
Journal of the Society for Information Display, Vol. 22, No. 7, pp.
329–336, July 2014.
Some stereoblind observers do not perceive depth of 3D stimuli
that depend on binocular disparity. These individuals, who have nodisabilities, comprise over 5% of the general population. In addition,
17.30% of non-stereoblind young (17–24 years old) and young–middle aged (25–39 years old) people do not use disparity information incertain 3D environments, a phenomenon known as pseudo-stereoblindness. This study aimed to investigate the relationshipbetween aging and the proportion of pseudo-stereoblindness in thegeneral population.

K. Miyaji, K. Kihara, J. Shimamura, Y. Taniguchi, and S. Ohtsuka
Proc. of the 10th Asia-Pacific Conference on Vision (APCV 2014),
p. 304, Takamatsu City, Kagawa, Japan, July 2014.
Since augmented reality (AR) is rapidly becoming popular, it isimportant to determine how visual information appears on different
depth planes. Object substitution masking (OSM) is a phenomenon
in which a target is masked by surrounding dots that remain after thetarget is offset, which depends on the division of attention. Our previous OSM study focused on a target and masking dots that were presented on different depth planes. It suggested that OSM was attenuated when participants observed binocularly, where depth cues ofvergence, disparity, and accommodation were available simultaneously. However, it is still unclear whether OSM is affected by thedepth difference between the target and masking dots if either vergence and disparity or accommodation can be used as depth cue(s).
To address this issue, we investigated the visibility of a target in OSM
with depth separation between the target and masking dots undermonocular and stereopsis viewings.

Load-adaptive Indexing Method for Schema-less Searches
Y. Arakawa, T. Nakamura, M. Nakamura, N. Matsuura, Y. Kawakita, and H. Ichikawa
Proc. of the 2014 IEEE 38th International Computer Software andApplications Conference Workshop (COMPSACW ’14), pp. 318–
324, Västerås, Sweden, July 2014.
UBI-Tree predicts usage frequencies of each query based on thecharacteristics of the stored data, and classifies incoming data in thetree so as to improve the search performance of frequently used queries. We propose a new method which improves the search performance of UBI-Tree based on the real load by using a query history.
We also experimentally show that the proposed method can improve
the average latency and throughput of search processes.

The Effect of Depth Information on Visual Attention under
Monocular and Stereopsis Viewings: An Object Substitution Masking Study

Vol. 13 No. 5 May 2015



Papers Published in Technical Journals and Conference Proceedings

Experimental Evaluation of Chromostereopsis with Varying Center Wavelength and FWHM of Spectral Power Distribution
M. Tsuchida, K. Kashino, and J. Yamato
Proc. of the 16th International Symposium on Multispectral
Colour Science (MCS 2014), pp. 133–141, Cherbourg, France, June/
July 2014.
This paper experimentally shows how the center wavelength andspectral power distribution (SPD) of displayed color is related tochromostereopsis (CS). CS is a visual illusion whereby the impression of depth is conveyed in two-dimensional color images. CS canbe applied to glassless binocular stereopsis by controlling color saturation even when a commercial liquid crystal display (LCD) is used
to display a two-dimensional image. We conducted evaluations ofstereoscopic visual effects among monochrome images using an
LCD panel and three monochrome backlights whose SPD had a single peak. The center wavelength and full width at half maximum(FWHM) of the SPD for the backlight were varied. The experimental
results show that CS does not occur strongly when the FWHM of abacklight is larger than 100 nm. We also suggest that the impressionof the depth for monochrome images depends on the center wavelength and FWHM of the color, which indicates CS can be expressedby the chromatic aberration.

Asymptotic Local Hypothesis Testing between a Pure
Bipartite State and the Completely Mixed StateM. Owari and M. Hayashi
Physical Review, Vol. 90, No. 032327, pp. 1–18, September
2014.
In this paper, we treat asymptotic hypothesis testing between an
arbitrary fixed bipartite pure state |Ψ and the completely mixed state
by one-way local operations and classical communication (LOCC),
two-way LOCC, and separable positive operator-valued measures(POVMs). As a result, we derive single-letterized formulas for the
Stein’s lemma type of optimal error exponents under one-way
LOCC, two-way LOCC, and separable POVMs, the Chernoff bounds
under one-way LOCC POVMs and separable POVMs, and the
Hoeffding bounds under one-way LOCC POVMs in the whole regionof a parameter and under separable POVMs in a restricted region ofa parameter. We also numerically calculate the Chernoff and the
Hoeffding bounds under a class of three-step LOCC protocols in lowdimensional systems and show that these bounds not only outperformthe bounds for one-way LOCC POVMs but also almost approximate
the bounds for separable POVMs in the parameter region where analytical bounds for separable POVMs are derived.

Fast Signal Reconstruction from Magnitude Spectrogramof Continuous Wavelet Transform Based on Spectrogram
Consistency
T. Nakamura and H. Kameoka
Proc. of the 17th International Conference on Digital Audio
Effects (DAFx-14), pp. 129–135, Erlangen, Germany, September
2014.
The continuous wavelet transform (CWT) can be seen as a filterbank having logarithmic frequency subband spacing similar to thehuman auditory system. Thus, to make computers imitate the significant functions of the human auditory system, one promising approach
would be to model, analyze, and process magnitude spectrograms
given by the CWT. To realize this approach, we must be able to convert a processed or modified magnitude CWT spectrogram, which

contains no information about the phase, into a time domain signal
specifically for those applications in which the aim is to generate
audio signals. To this end, this paper proposes a fast algorithm forestimating the phase from a given magnitude CWT spectrogram toreconstruct an audio signal.

Joint Audio Source Separation and Dereverberation
Based on Multichannel Factorial Hidden Markov Model
T. Higuchi and H. Kameoka
Proc. of the 2014 IEEE International Workshop on Machine Learning for Signal Processing (MLSP 2014), Reims, France, September
2014.
This paper proposes a unified approach for jointly solving underdetermined source separation, audio event detection, and dereverberation of convolutive mixtures. We previously proposed an extension of multichannel NMF (nonnegative matrix factorization), in
which the variations over time of the spectral density and the total
power of each source are modeled by a hidden Markov model(HMM). This has allowed us to conduct source activity detection andsource separation simultaneously through model parameter inference. While this method was based on an anechoic mixing model, theaim of this paper is to further extend the above approach to deal withreverberation by incorporating an echoic mixing model into the generative model of observed signals.

Maximum Reconstruction Probability Training of Restricted Boltzmann Machines with Auxiliary Function
Approach
N. Takamune and H. Kameoka
Proc. of MLSP 2014, Reims, France, September 2014.
Restricted Boltzmann machines (RBMs) are stochastic neuralnetworks that can be used to learn features from raw data. They haveattracted particular attention recently after being proposed as building blocks for deep belief networks (DBNs) and have been appliedwith notable success in a range of problems including speech recognition and object recognition. The success of these models raises theissue of how best to train them. At present, the most popular training
algorithm for RBMs is the Contrastive Divergence (CD) learningalgorithm. We propose deriving a new training algorithm based on an
auxiliary function approach for RBMs using the reconstruction probability of observations as the optimization criterion. Through anexperiment on parameter training of an RBM, we confirmed that thepresent algorithm outperformed the CD algorithm in terms of theconvergence speed and the reconstruction error when used as an
autoencoder.

Training Restricted Boltzmann Machines with Auxiliary
Function Approach
H. Kameoka and N. Takamune
Proc. of MLSP 2014, Reims, France, September 2014.
Restricted Boltzmann machines (RBMs) are neural network models for unsupervised learning, but have recently found a wide range
of applications as feature extractors for supervised learning algorithms. They have also received a lot of attention recently after being
proposed as building blocks for deep belief networks. The success ofthese models raises the issue of how best to train them. At present, themost popular training algorithm for RBMs is the Contrastive Divergence (CD) learning algorithm. The aim of this paper is to seek a new

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

optimization algorithm tailored for training RBMs in the hope ofobtaining a faster algorithm than the CD algorithm. We propose
deriving a new training algorithm for RBMs based on an auxiliary
function approach. Through an experiment on parameter training ofan RBM, we confirmed that the present algorithm converged fasterand to a better solution than the CD algorithm.

A Unified Approach for Underdetermined Blind Signal
Separation and Source Activity Detection by Multichannel
Factorial Hidden Markov Models
T. Higuchi, H. Takeda, T. Nakamura, and H. Kameoka
Proc. of the 15th Annual Conference of the International SpeechCommunication Association (Interspeech 2014), Singapore, September 2014.
This paper introduces a new model called the multi-channel factorial hidden Markov model (MFHMM) for underdetermined blind
signal separation (BSS). We propose extending the multichannel
NMF model by modeling the transition of the set consisting of thespectral densities and the total power of each source using a hidden
Markov model (HMM). By letting each HMM contain states corresponding to active and inactive modes, we will show that voice activity detection and source separation can be solved simultaneously
through parameter inference of the present model.

Speech Prosody Generation for Text-to-speech Synthesis
Based on Generative Model of F0 Contours
K. Kadowaki, T. Ishihara, N. Hojo, and H. Kameoka
Proc. of Interspeech 2014, Singapore, September 2014.
This paper deals with the problem of generating the fundamental
frequency (F0) contour of speech from a text input for text-to-speechsynthesis. We previously introduced a statistical model describing thegenerating process of speech F0 contours, based on the discrete-timeversion of the Fujisaki model. One remarkable feature of this modelis that it has allowed us to derive an efficient algorithm based on
powerful statistical methods for estimating the Fujisaki model
parameters from raw F0 contours. To associate a sequence of theFujisaki model parameters with a text input based on statistical learning, this paper proposes extending this model to a context-dependentone. We further propose a parameter training algorithm for the present model based on decision tree-based context clustering.

Development of Wideband Handset for High Quality IP
Telephone Service Trial
M. Okamoto, K. Noguchi, Y. Hiwasaki, and Y. Haneda
Proc. of the 2014 IEEE 3rd Global Conference on Consumer Electronics (GCCE 2014), pp. 523–524, Chiba, Japan, October 2014.
Since 2007, high quality IP telephone service has been provided
over a Next Generation Network (NGN) developed by Nippon Telegraph and Telephone Corporation (NTT) Group of Japan. Prior to thecommencement of service provision, a wideband telephone handset
was developed on an experimental basis and tested in a field trial toverify service validity. The handset demonstrated improved characteristics over those of conventional telephone handsets.

Vol. 13 No. 5 May 2015

Harmonic-temporal Factor Decomposition Incorporating
Music Prior Information for Informed Monaural Source
Separation
T. Nakamura, K. Shikata, N. Takamune, and H. Kameoka
Proc. of the 15th International Society for Music Information
Retrieval Conference (ISMIR 2014), pp. 623–628, Taipei, Taiwan,
October 2014.
For monaural source separation, two main approaches have thus
far been adopted. One approach involves applying non-negative
matrix factorization (NMF) to an observed magnitude spectrogram,which is interpreted as a non-negative matrix. The other approach isbased on the concept of computational auditory scene analysis(CASA). A CASA-based approach called harmonic-temporal clustering (HTC) aims to cluster the time-frequency components of anobserved signal based on a constraint designed according to the local
time-frequency structure common in many sound sources (such as
harmonicity and the continuity of frequency and amplitude modulations). This paper proposes a new approach for monaural source
separation called Harmonic-Temporal Factor Decomposition(HTFD) by introducing a spectrogram model that combines the features of the models employed in the NMF and HTC approaches. We
further describe some ideas on how to design the prior distributions
for the present model to incorporate musically relevant information
into the separation scheme.

Efficient POC-based Correspondence Detection Method
for Multi-channel Images
M. Tsuchida, S. Sakai, K. Ito, K. Kashino, J. Yamato, and T. Aoki
Proc. of the 22nd Color and Imaging Conference, pp. 113–118,
Boston, MA, USA, November 2014.
We propose a new phase-only correlation (POC)-based high-accuracy correspondence detection method for multi-channel images.
There is the possibility of improving detection accuracy because
conventional POC-based methods do not use color information. In
the proposed method, a normalized cross spectrum (or cross-phase
spectrum) and weight are calculated for each color channel in the
Fourier domain. The weight is determined by the amplitude of thecross spectrum. The weighted normalized cross spectra of all color
channels are combined, and inverse Fourier transformation is conducted to obtain a POC function. An experimental evaluation of thematching accuracy between the conventional POC-based method andthe proposed method shows that RMSE (root-mean-square error)
decreased approximately 25%. This paper also describes an application of the proposed method to stereo image matching. The average
detection ratio of correspondences between a stereo-pair image is
improved 64% to 95%.

Harmonic/Percussive Sound Separation Based on Anisotropic Smoothness of Spectrograms
H. Tachibana, N. Ono, H. Kameoka, and S. Sagayama
IEEE/ACM Transactions on Audio, Speech, and Language Processing, Vol. 22, No. 12, pp. 2059–2073, December 2014.
This paper describes a method to separate a monaural music signal
into harmonic components, e.g., a guitar and percussive components
such as a snare drum. Separation of these two components is a usefulpreprocessing step for many music information retrieval applications,and in addition, it can be used as a new kind of music equalizer in
itself, which enables a music listener to freely adjust the ratio of thevolume of the guitar and the drum by themselves.

Papers Published in Technical Journals and Conference Proceedings

Wideband Injection Locked CMOS Quadrature Ring Oscillator with Small Phase Errors
N. Jahan, A. Anand, T. Kaho, K. Yousef, and R. K. Pokharel
Proc. of the 2014 Korea-Japan Microwave Workshop (KJMW2014),
Suwon, Korea, December 2014.
This paper presents a wideband low phase noise complementary
metal-oxide-semiconductor (CMOS) quadrature ring oscillator. It
employs a novel technique to improve phase errors by single pulse
injection with three dummy transistors. The analysis was verified bymodels in a 0.18-μm CMOS process. The simulation results showthat the phase errors can be minimized within ± 1 degree. It has awide tuning range from 0.3 GHz to 5.8 GHz at free-run oscillation,and low phase noise with −136.8dBc/Hz @1MHz offset at 5.25-GHz
oscillation with injection locking.

Unified Approach for Underdetermined BSS, Source Activity Detection, Dereverberation and DOA Estimation with
Multichannel Factorial HMM
T. Higuchi and H. Kameoka
Proc. of the 2014 IEEE Global Conference on Signal and Information Processing (GlobalSIP), Atlanta, GA, USA, December 2014.
This paper proposes a novel method for simultaneously solving the
problems of underdetermined blind source separation (BSS), source
activity detection, dereverberation, and direction-of-arrival (DOA)
estimation by introducing an extension of the multichannel factorial
hidden Markov model (MFHMM).

Full Information Maximum Likelihood Estimation in Factor
Analysis with a Large Number of Missing Values
K. Hirose, S. Kim, Y. Kano, M. Imada, M. Yoshida, and M. Matsuo
Journal of Statistical Computation and Simulation, January 2015.
We consider the problem of full information maximum likelihood(FIML) estimation in factor analysis when a majority of the data
values are missing. The expectation–maximization (EM) algorithm isoften used to find the FIML estimates, in which the missing values on
manifest variables are included in the complete data. However, theordinary EM algorithm has an extremely high computational cost. In
this paper, we propose a new algorithm that is based on the EM algorithm but that efficiently computes the FIML estimates. A significant
improvement in the computational speed is realized by not treating
the missing values on manifest variables as a part of the complete
data. When there are many missing data values, it is not clear if the
FIML procedure can achieve good estimation accuracy. In order toinvestigate this, we conduct Monte Carlo simulations under a wide
variety of sample sizes.

Quantum Algorithms for Finding Constant-sized Subhypergraphs
F. L. Gall, H. Nishimura, and S. Tani
Proc. of the 18th Conference on Quantum Information Processing(QIP 2015), Sydney, Australia, January 2015.
We develop a general framework to construct quantum algorithms
that detect if a 3-uniform hypergraph given as input contains a subhypergraph isomorphic to a prespecified constant-sized hypergraph.
This framework is based on the concept of nested quantum walks
recently proposed by Jeffery, Kothari, and Magniez [SODA’13], andextends the methodology designed by Lee, Magniez, and Santha

[SODA’13] for similar problems over graphs. As applications, we
obtain a quantum algorithm for finding a 4-clique in a 3-uniform
hypergraph on n vertices with query complexity O(n1.883), and aquantum algorithm for determining if a ternary operator over a set ofsize n is associative with query complexity O(n2.113).

Estimating Spectral Reflectance of Fabrics from Highresolution Multi-band HDR Images
S. Tanaka, A. Takayanagi, M. Tsuchida, Y. Sakaguchi, and H. T.
TanakaProc. of the 21st Korea-Japan joint Workshop on Frontiers of Computer Vision (FCV 2015), Mokpo, Korea, January 2015.
We present a spectral reflectance estimation method of high reflectance targets such as fabrics compared with training samples. We
show the efficacy from the results of comparing the proposed method
and the conventional method. In addition, the spectral reflectance ofpolyester satin fabric was estimated from high-resolution multi-band
high dynamic range (HDR) images. The spectral reflectance including object color was observed strongly in the weft central region.

Probabilistic Modeling of Pitch Contours towards Prosody
Synthesis and Conversion
H. Kameoka
Speech Prosody in Speech Synthesis, pp. 49–69, February 2015.
Since the voice fundamental frequency (F0) contour is an important acoustic correlate of many prosodic constructs, modeling andanalyzing F0 contours can be potentially useful for many speech
applications such as speech synthesis, speaker identification, speech
conversion, and dialogue systems, in which prosodic information
plays a significant role. In this chapter, we formulate a statisticalmodel of F0 contours by translating the “Fujisaki model,” a wellfounded mathematical model representing the control mechanism of
vocal fold vibration, into a probabilistic model described as a discrete-time stochastic process.

Highly Realistic 3D Display System for Space Composition Telecommunication
M. Date, H. Takada, Y. Honda, S. Ozawa, S. Mieda, and A. Kojima
Journal of Display Technology, Vol. 11, No. 2, pp .121–128, February 2015.
In this paper, we describe a highly realistic 3D display system thatgenerates composites of current and remote places for telecommunication purposes. It uses a 3D projector and head tracking to display aperson in a remote place as a life-size stereoscopic image against
background scenery. Since it generates displayed images that correspond to the observer’s viewing position, it reproduces well the fidelity of existence and the feel of materials. We also describe a simple,
fast, and high quality background scenery generation method, thedevelopment of which was inspired by the visual effects of depthfused 3D (DFD) displays, and applied it to a single direction conceptual demonstration system. Our system is a promising means ofachieving real-time communication between two different places incases where a sense of reality is required.

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

Impossibility of Classically Simulating One-clean-qubit
Computation
K. Fujii, H. Kobayashi, T. Morimae, H. Nishimura, S. Tamate, and
S. TaniarXiv:1409.6777v2 [quant-ph], February 2015.
Deterministic quantum computation with one quantum bit (DQC1)
is a restricted model of quantum computing where the input state is acompletely mixed state except for a single clean qubit, and only asingle output qubit is measured at the end of the computing. It is
proved that the restriction of quantum computation to the DQC1
model does not change the complexity classes NQP (Nondeterministic Quantum Polynomial-Time) and SBQP (Small Bounded-Error
Quantum Polynomial-Time). As the main consequence, it follows
that the DQC1 model cannot be efficiently simulated by classicalcomputers unless the polynomial-time hierarchy collapses to thesecond level (more precisely, to AM), which answers the long-standing open problem posed by Knill and Laflamme under the very
plausible complexity assumption. The argument developed in thispaper also weakens the complexity assumption necessary for the
existing impossibility results on classical simulation of various subuniversal quantum computing models, such as the IQP (intuitive
quantum physics) model and Boson sampling.

Wavelength-tunable Filter Utilizing Non-cyclic Arrayed
Waveguide Grating to Create Colorless/Directionless/Contentionless ROADMs
M. Niwa, S. Takashina, Y. Mori, H. Hasegawa, K. Sato, and T.
WatanabeProc. of SPIE Photonics West, 938807, San Francisco, CA, USA,
February 2015.
We propose here novel tunable-filter architecture that sandwiches
a single-stage non-cyclic athermal AWG (arrayed waveguide grating)having flatter-topped passbands between small-scale switches. With
this configuration, the optical tunable filter attains low insertion loss,
large passband bandwidths, low power consumption, compactness,and high cost-effectiveness. A prototype was monolithically fabricated with PLC (planar-lightwave-circuit) technologies, and its
excellent performance was experimentally confirmed utilizing 80channel 30-GBaud dual-polarization QPSK (quadrature phase-shiftkeying) signals.

March 2015.
Possible configurations of tunable components for the next-generation passive optical network stage 2 (NG-PON2) are reviewed on
the basis of system requirements. Expected network functions in NGPON2 systems along with the concept of in-service tuning in colorless ONUs are also reviewed.

Designing Overlay Networks for Handling Exhaust Data ina Distributed Topic-based Pub/Sub Architecture
R. Banno, S. Takeuchi, M. Takemoto, T. Kawano, T. Kambayashi,
and M. Matsuo
Journal of Information Processing, Vol. 23, No. 2, pp. 105–116,
March 2015.
To provide event-driven services in IoT, scalable methods of topicbased pub/sub messaging are indispensable. Methods using structured overlay networks are promising candidates. However, existing
methods have the problem of wasting network resources, because
they lack adaptivity to “exhaust data,” which have low or no value
most of the time. This problem has two aspects. One is that eachpublisher node continues to forward data to a relay node even if there
are no subscribers. The other is that excessively large multicast trees
are constructed for low value data, which will be received by only asmall number of subscribers. In this paper, we formulate the desirable
design of overlay networks by defining a property called “strong
relay-free” as an expansion of the relay-free property. The property
involves publishers and subscribers composing connected subgraphs
to enable detection of the absence of subscribers and autonomous
adjustment of the tree size. We also propose a practical method satisfying the property by using Skip Graph, which we valuated throughsimulation experiments. We confirmed that the proposed method cansuspend publishing adaptively and shorten the path length on multicast trees by more than 75% under an experimental condition with
100,000 nodes.

Real-time Viewpoint Image Synthesis Using Strips ofMulti-camera Images
M. Date, H. Takada, and A. Kojima
Proc. of SPIE Photonics West, 939109, San Francisco, CA, USA,
February 2015.
A real-time viewpoint image generation method is achieved. Video
communications with a high sense of reality are needed to makenatural connections between users in different places. In this paper,
we propose a real-time viewpoint image generation method using
simple blending of multiple camera images taken at equal horizontal
intervals and convergence obtained by using approximate information of an object’s depth.

Non-linear Matrix Factorization for Group Recommendation
Y. Yoshikawa, T. Iwata, and H. Sawada
Transactions of the Japanese Society for Artificial Intelligence,Vol. 30, No. 2, pp. 485–490, March 2015.
Group recommendation is a task to recommend items to groups
such as households and communities. In this paper, we propose anonlinear matrix factorization method for group recommendation.
The proposed method assumes that each member in a group has its
own latent vector, and the behavior of each group is determined by
the probability distribution of the members’ latent vectors. Recommendations of items are performed by using nonlinear functions that
map the distributions of the groups into scores for items. The nonlinear functions are generated from Gaussian processes, which aredefined by the similarities between distributions of the groups. We
can efficiently calculate the similarities by embedding each distribution as an element in a reproducing kernel Hilbert space. We demonstrate the effectiveness of the method using two synthetic datasetsand two real datasets in two prediction tasks.

Consideration of Tunable Components for Next-generation Passive Optical Network Stage 2
K. Asaka
Journal of Lightwave Technology, Vol. 33, No. 5, pp. 1072–1076,

Dense Space Division Multiplexed Transmission overMulti-core and Multi-mode Fiber
T. Mizuno, H. Takara, A. Sano, and Y. Miyamoto
Proc. of the Optical Fiber Communication Conference and Exposi-Vol. 13 No. 5 May 2015



Papers Published in Technical Journals and Conference Proceedings

tion (OFC) 2015, Th1D.2, San Francisco, CA, USA, March 2015.
We review recent progress in space division multiplexed (SDM)
transmission and examine our experimental demonstration of dense
SDM (DSDM) using both multi-core and multimode, which provide
a key advance to ultra-high capacity transmission.

Large-scale Optical-switch Prototype Compactly Implemented with Novel Functional Configuration
K. Ueda, Y. Mori, H. Hasegawa, K. Sato, and T. Watanabe
Proc. of OFC 2015, W3D.1, San Francisco, CA, USA, March2015.
We propose a novel optical-switch architecture that can be compactly implemented with a novel functional configuration. A highly
integrated 180 × 180 optical switch prototype was fabricated using
planar-lightwave-circuit technologies, and its good performance wasexperimentally confirmed.

Demonstration of Large-port-count and Compact ROADM
that Exhibits Virtual-C/D/C Performance
S. Takashina, H. Ishida, Y. Mori, H. Hasegawa, K. Sato, T. Watanabe
Proc. of OFC 2015, W3J.6, San Francisco, CA, USA, March2015.
We demonstrate novel large-scale and cost-effective reconfigurable optical add-drop multiplexer (ROADM) architecture that

exploits the subsystem-modular express switches and tailored transponder banks for add/drop functionality. Simulations show that the
proposed ROADM offers virtual-C/D/C performance. Good transmission characteristics are experimentally confirmed.

Photospectroscopically Observed Pore-space Correlations of a Wetting Fluid during the Drying Process in Nanoporous Vycor Glass
S. Ogawa and J. Nakamura
Journal of the Optical Society of America A, Vol. 32, No. 4, pp.
533–537, April 2015.
We use light scattering to study spatial correlations in the porespace of Vycor glass upon draining a wetting fluid. We analyze thetransmission spectrum of forward-scattered light on the basis of thetheory of dielectric constant fluctuation, whereas conventional lightscattering analyzes the scattered light at small angles of monochromatic incident light. Assuming that the drained pores, which aresurrounded by filled pores, exhibit long-range correlations of a fractal
dimension of 2.5, we analytically derive the corresponding turbidity.
The slight deviation from the λ−4 Rayleigh wavelength dependence
directly provides the correlation length of the interconnected networkof drained pores. The estimated length, ranging from 0.5 nm to 18 nm
at most, is almost the same order as that indirectly estimated from ourprevious simple but effective Rayleigh scattering model.

NTT Technical Review