External Awards
MTRAJ Award
Winner: Akira Ito, NTT Access Network Service Systems Laboratories; Hiroyuki Saito, Tokyo Denki University; Takanobu Suzuki,Toyo University
Date: April 20, 2015
Organization: Material Testing Research Association of Japan(MTRAJ)For “Quantification of Seismic Performance Deterioration Caused
by Corrosion on a Telecommunication Conduit.”
Published as: A. Ito, H. Saito, and T. Suzuki, “Quantification ofSeismic Performance Deterioration Caused by Corrosion on a Telecommunication Conduit,” Journal of Material Testing Research
Association of Japan, Vol. 59, No. 4, pp. 188–193, Oct. 2014.
2014 LOIS Research AwardWinner: Shigeki Takeuchi and Goro Inomae, NTT Service Evolution Laboratories; Manabu Okamoto, NTT Media Intelligence Laboratories; and Hiroyuki Tate, NTT Service Evolution Laboratories
Date: April 22, 2015
Organization: Institute of Electronics, Information and Communication Engineers (IEICE), Information and Systems Society, Technical Committee on Life Intelligence and Office Information Systems(LOIS)
For “The Tourist Information System for the Route Bus withSmartphone—the Evaluation Result Report on the Bus Line—.”Buses for tourists are used in tourist resorts. We are developing asystem that provides passengers with route sightseeing information
so that buses do not need a guide on board or special digital signage
equipment. In this paper, a tourist information system is proposedthat is integrated with the location of a bus and shows users necessary
details from a large amount of sightseeing information. An evaluation
using an experimental system is also described.
Published as: S. Takeuchi, G. Inomae, M. Okamoto, and H. Tate,“The Tourist Information System for the Route Bus with Smartphone—the Evaluation Result Report on the Bus Line—,” IEICE
Tech. Rep., Vol. 114, No. 150, LOIS2014-15, pp. 23–28, Jul. 2014.
45th Senken Gousen Prize New Frontier Award
Winner: Nippon Telegraph and Telephone Corporation and TorayIndustries, Inc.
Date: April 24, 2015
Organization: Senken Shimbunsha
For the development of conductive fabric called hitoe that enables
continuous measurement of the biological signals of the person wearing it.

IEICE Communications Society Best Tutorial Paper Award(Japanese edition)
Winner: Yusuke Asai, NTT Network Innovation Laboratories; Koichi Ishihara, Tomoki Murakami, Riichi Kudo, Takeo Ichikawa, Yasushi Takatori, and Masato Mizoguchi, NTT Access Network Service
Systems Laboratories
Date: May 15, 2015
Organization: IEICE, Communications SocietyFor “Overview of Very High Throughput Wireless LAN Standard
IEEE 802.11ac and Experimental Evaluation of Multiuser-MIMOTransmission.”
Published as: Y. Asai, K. Ishihara, T. Murakami, R. Kudo, T. Ichikawa, Y. Takatori, and M. Mizoguchi, “Overview of Very HighThroughput Wireless LAN Standard IEEE 802.11ac and Experimental Evaluation of Multiuser-MIMO Transmission,” The Transactionsof the Institute of Electronics, Information and Communication Engineers. B, Vol. J97-B, No. 1, pp. 1–18, Jan. 2014.
ITU-AJ International Corporation Award
Winner: Atsushi Takahara and Toshikazu Sakano*, NTT Network
Innovation Laboratories*	Currently, he is with Advanced Telecommunications ResearchInstitute International (ATR).

Date: May 15, 2015
Organization: The ITU Association of Japan (ITU-AJ)
For the development of the information and communication technology (ICT) architecture called the movable and deployable ICT
resource unit (MDRU) that enables instant recovery of telecommunications services in damaged areas. In addition, they conducted afeasibility study on the effectiveness of MDRUs in disaster-stricken
areas in the Philippines under an International Telecommunication
Union (ITU) project. They also actively worked on standardization
efforts within ITU in order to promote broad use of MDRUs.
ISCIE Encouragement Prize
Winner: Masaya Murata, NTT Communication Science Laboratories
Date: May 21, 2015
Organization: Institute of Systems, Control and Information Engineers (ISCIE)
For “Gaussian Unscented Filter.”
Published as: M. Murata, H. Nagano, and K. Kashino, “GaussianUnscented Filter,” Proc. of the 46th ISCIE International Symposiumon Stochastic Systems Theory and Its Applications (SSS’14), Kyoto,
Japan, Nov. 2014.

NTT Technical Review

Papers Published in Technical Journals andConference Proceedings
A Spectrum- and Energy-efficient Scheme for Improving
the Utilization of MDRU-based Disaster Resilient Networks
T. Ngo, H. Nishiyama, N. Kato, T. Sakano, and A. Takahara
IEEE Transactions on Vehicular Technology, Vol. 63, No. 5, pp.
2027–2037, June 2014.
The lack of spectrum and energy resources is a major problem in
movable and deployable resource unit (MDRU)-based networks,
where the throughput requirement is very high. In this paper, we
propose a scheme to improve the utilization of both spectrum andenergy resources to increase performance in the gateway portion ofthe MDRU-based network.

Attenuators Enable Inversely Proportional Setting Transmission Power and Carrier Sense Threshold in WLANs
D. Okuhara, F. Shiotani, K. Yamamoto, T. Nishio, M. Morikura, R.
Kudo, and K. Ishihara
Proc. of the 25th International Symposium on Personal Indoor andMobile Radio Communications (IEEE PIMRC 2014), pp. 986–990,
Washington DC, USA, September 2014.
The insertion of attenuators between transceivers and antennas is
proposed in order to improve spatial channel reuse in carrier sense
multiple access with collision avoidance based wireless local area
networks (WLANs). Using attenuators enables the access points orstations to reduce the power levels of transmission signals andreceived signals, which results in an increase in the carrier sense
threshold. Thus, the attenuation value control enables inversely proportional setting of the transmission power and carrier sense threshold, which is known to provide a novel solution for the unfairness
problem caused by variable transmission power or variable carrier
sense threshold. We first derive a simple and effective condition suchthat the aggregate spectral efficiency is higher when attenuators areused than they are when using some approximations. Through anumerical evaluation as well as a testbed for using attenuators, thecondition is shown to be valid despite using the approximations, andthroughput improvement is verified. The result from the testbed also
disclosed a new unfairness problem due to individual differences intransmission power or carrier sense threshold.

AP Cooperative Diversity in Wireless Network Using Interference-aware Channel Segregation Based Dynamic
Channel Assignment
M. T. H. Sirait, Y. Matsumura, K. Temma, K. Ishihara, B. A. H. S.
Abeysekera, T. Kumagai, and F. Adachi
Proc. of IEEE PIMRC 2014, pp. 1185–1189, Washington DC,USA, September 2014.
Recently, we proposed interference-aware channel segregation
based dynamic channel assignment (IACS-DCA) which forms achannel reuse pattern with low co-channel interference (CCI) in a
distributed manner. The transmission performance of a wireless station (STA) located far from access points (APs) degrades due to pathloss and shadowing loss. AP cooperative diversity is a well-known
technique to improve the transmission performance. Since IACSDCA operates so as to assign different channels to different APs

Vol. 13 No. 7 July 2015

located nearby each other, it is not an easy task to introduce AP cooperative diversity to a wireless network using IACS-DCA. In thispaper, we propose an AP grouping and channel selection method for
AP cooperative diversity in a wireless network using IACS-DCA. By
computer simulation, we show that the proposed AP cooperative
diversity can improve the transmission performance.

Broadband Spectrum Sensing Platform Based on
Received Waveform Cross-correlation Using DistributedSensors
T. Yamada, D. Lee, H. Shiba, Y. Yamaguchi, T. Kaho, T. Nakagawa,and K. UeharaProc. of SmartCom (Singapore - Japan International Workshop on
Smart Wireless Communications) 2014, Singapore, October 2014.
The rapid increase in mobile traffic due to the spread of smartphones is expected to cause a frequency shortage. The frequency
range from 400 MHz to 6 GHz has been allocated to various wirelesssystems in Japan. Therefore, the use of white space technology isexpected, and many studies on it have been reported. We present a
broadband spectrum sensing platform for a white space system thatcovers a frequency range from 400 MHz to 6 GHz. In our platform,
we elaborated and implemented a cooperative sensing method thatexploits cross-correlations of received signals among distributed sensors to estimate the received signal strength. This method enables us
to detect signals under the noise floor (e.g., –114 dBm/6 MHz
according to Federal Communications Commission rules), to identify
transmitters, and to recognize the border of radio coverage. We developed a prototype of our platform and successfully verified its performance.

An Advanced Wi-Fi Data Service Platform Coupled with aCellular Network for Future Wireless Access
R. Kudo, Y. Takatori, B. A. H. S. Abeysekera, Y. Inoue, A. Murase,A. Yamada, H. Yasuda, and Y. Okumura
IEEE Communications Magazine, Vol. 53, No. 11, pp. 46–53,
November 2014.
Wireless LAN (local area network) devices are now everywhere
because of the rapid spread of smart wireless devices. Demand for far
richer content services is also driving the expansion of mobile traffic.
Converging the cellular network with Wi-Fi is a reasonable way tosupport the increasing mobile traffic because most mobile user terminals already have Wi-Fi interfaces. Creating more opportunities for
Wi-Fi use will require further enhancement of system capacity andmanageability, especially in the high-density Wi-Fi network. This isbecause the chronic depletion of system resources is becoming asignificant problem in the Wi-Fi network given the increases in Wi-Fi
density and traffic. This article introduces a Wi-Fi data service platform coupled with cellular networks, which strengthens the synergyof two networks. Enhanced monitoring and performance prediction
are essential to provide a high-grade user experience in high-density
Wi-Fi environments.

Papers Published in Technical Journals and Conference Proceedings

Cooperative Inter-cell Interference Mitigation Scheme withDownlink MU-MIMO Beamforming for Dense Wireless LAN
Environment
K. Ishihara, T. Murakami, Y. Asai, Y. Takatori, and M. Mizoguchi
Wireless Personal Communications, DOI: 10.1007/s11277-0142220-2, December 2014.
A cooperative inter-cell interference (ICI) mitigation scheme withtransmit beamforming for dense wireless LAN systems is proposed.
The proposed scheme applies transmit beamforming used for downlink multi-user multiple-input and multiple-output (MU-MIMO) inorder to mitigate the effect of ICI and selectively determines whether
an access point (AP) performs null beamforming for each station(STA) in overlapping basic service sets (OBSSs) according to the ICIpower. Null beamforming is used to suppress ICI if its power exceeds
a threshold; otherwise, it is not carried out and the transmit antenna
is used to obtain a diversity gain for STAs associated with the AP.
Computer simulations confirmed that the achievable rate obtainedwith the proposed scheme is superior to that obtained with either time
resource sharing or conventional ICI mitigation in an OBSS environment.

Experimental Validation of Digital Pre-distortion Techniquefor Dual-band Dual-signal Amplification by Single Feedback Architecture Employing Dual-band Mixer
I. Ando, G. K. Tran, K. Araki, T. Yamada, T. Kaho, Y. Yamaguchi,
and T. Nakagawa
IEICE Transactions on Electronics, Vol. E98-C, No. 3, pp. 242–251, March 2015.
In this paper, we propose and experimentally validate a dual-banddigital predistortion (DPD) model that takes account of the intermodulation and harmonic distortion produced when the center frequencies of input bands have a harmonic relationship. We also
describe and experimentally validate our proposed novel dual-band
power amplifier (PA) linearization architecture consisting of a single
feedback loop employing a dual-band mixer. Experiment results
show that the DPD linearization the proposed model provides cancompensate for intermodulation and harmonic distortion in a waythat the conventional two-dimensional (2-D) DPD approach cannot.
The proposed feedback architecture should make it possible to simplify analog-to-digital converter (ADC) design and eliminate the timelag between different feedback paths.

A Novel Application of Massive MIMO: Massive Antenna
Systems for Wireless Entrance (MAS-WE)
K. Maruta, A. Ohta, S. Kurosaki, T. Arai, and M. Iizuka
Proc. of ICNC (International Conference on Computing, Networking and Communications) 2015, Anaheim, USA, February 2015.
This paper proposes a practical application of Massive MIMO
technology, Massive Antenna Systems for Wireless Entrance (MASWE), and its related inter-user interference (IUI) cancellation andscheduling techniques. MAS-WE, on which the entrance base station(EBS) employs a large number of antennas, can effectively provide
high capacity wireless entrance links to a large number of Wi-Fi
access points (APs) distributed in a wide coverage area. The proposed
techniques have been ultimately simplified to have less impact on
their practical implementation in order to spatially multiplex morethan 16 signal streams with around 100 antenna elements on the EBS
side. The SIR (signal-to-interference ratio) performance was evaluated by system level simulation considering imperfect channel state
information (CSI), and the results showed that the proposed MASWE with simplified techniques can achieve high spectral efficiency
with high level space division multiplexing.

Different Roles of the COMT and HTR2A Genotypes in
Working Memory Subprocesses
H. M. Kondo, M. Nomura, and M. Kashino
PLOS ONE, Vol. 10, No. 5, e012651, May 2015.
The present study used an imaging genetics approach to examine
the interaction between neurochemical functions and working memory performance. We focused on functional polymorphisms of thecatechol-O-methyltransferase (COMT) Val158Met and serotonin 2A
receptor (HTR2A) -1438G/A genes, and devised a delayed recognition task to isolate the encoding, retention, and retrieval processes ofvisual information. The COMT genotypes affected recognition accuracy, whereas the HTR2A genotypes were associated with responsetimes.

Dense Space Division Multiplexed Transmission TechnologyT. Mizuno, H. Takara, A. Sano, and Y. Miyamoto
CLEO (Conference on Lasers and Electro-Optics) 2015, SW4M. 1,San Jose, USA, May 2015.
We review recent progress in ultra-high capacity transmission
based on dense space division multiplexing (DSDM) for future scalable optical transport networks and present the latest multi-core
multi-mode fiber, spatial multi/demultiplexers, and MIMO signal
processing technique.

NTT Technical Review