Keisuke TSUNODA Akihiro CHIBA Kazuhiro YOSHIDA Tomoki WATANABE Osamu MIZUNO
In this paper, we propose a low-invasive framework to predict changes in cognitive performance using only heart rate variability (HRV). Although a lot of studies have tried to estimate cognitive performance using multiple vital data or electroencephalogram data, these methods are invasive for users because they force users to attach a lot of sensor units or electrodes to their bodies. To address this problem, we proposed a method to estimate cognitive performance using only HRV, which can be measured with as few as two electrodes. However, this can't prevent loss of worker productivity because the workers' productivity had already decreased even if their current cognitive performance had been estimated as being at a low level. In this paper, we propose a framework to predict changes in cognitive performance in the near future. We obtained three principal contributions in this paper: (1) An experiment with 45 healthy male participants clarified that changes in cognitive performance caused by mental workload can be predicted using only HRV. (2) The proposed framework, which includes a support vector machine and principal component analysis, predicts changes in cognitive performance caused by mental workload with 84.4 % accuracy. (3) Significant differences were found in some HRV features for test participants, depending on whether or not their cognitive performance changes had been predicted accurately. These results lead us to conclude that the framework has the potential to help both workers and managerial personnel predict what their performances will be in the near future. This will make it possible to proactively suggest rest periods or changes in work duties to prevent losses in productivity caused by decreases of cognitive work performance.
Siran ZHANG Zhiwei YAN Yong-Jin PARK Hidenori NAKAZATO Wataru KAMEYAMA Kashif NISAR Ag Asri Ag IBRAHIM
Named Data Networking (NDN) is a promising architecture for the future Internet and it is mainly designed for efficient content delivery and retrieval. However, producer mobility support is one of the challenging problems of NDN. This paper proposes a scheme which aims to optimize the tunneling-based producer mobility solution in NDN. It does not require NDN routers to change their routing tables (Forwarding Information Base) after a producer moves. Instead, the Interest packet can be sent from a consumer to the moved producer using the tunnel. The piggybacked Data packet which is sent back to the consumer will trigger the consumer to send the following Interest packets through the optimized path to the producer. Moreover, a naming scheme is proposed so that the NDN caching function can be fully utilized. An analysis is carried out to evaluate the performance of the proposal. The results indicate that the proposed scheme reduces the network cost compared to related works and supports route optimization for enhanced producer mobility support in NDN.
Shinichi TANAKA Kengo SAITO Toshiaki OKA Yodai SHIBOSAWA
Novel design approaches for microwave active circuits using composite right-/left-handed (CRLH) transmission line (TL) stubs are presented. We show that, by modifying the dispersion diagram of the CRLH TL stub, the frequency band or the harmonic tuning capability can be enhanced in such a way that it would have been difficult or impractical if done using conventional micro-strip line stubs. The frequency response of the CRLH TL stub can be controlled almost arbitrarily while at the same time reducing the stub length significantly, because the dispersion curve in the left-handed region and in the right-handed region is controlled independently. As a proof of concept, a triple-band rectifier, single-band and dual-band harmonic tuning circuits for class-F amplifiers are demonstrated.
Yuji UNAGAMI Natsume MATSUZAKI Shota YAMADA Nuttapong ATTRAPADUNG Takahiro MATSUDA Goichiro HANAOKA
In this paper, we propose a similarity searchable encryption in the symmetric key setting for the weighted Euclidean distance, by extending the functional encryption scheme for inner product proposed by Bishop et al. [4]. Our scheme performs predetermined encoding independently of vectors x and y, and it obtains the weighted Euclidean distance between the two vectors while they remain encrypted.
Zhihao ZHONG Jianhua PENG Kaizhi HUANG
In order to satisfy the very high traffic demand in crowded hotspot areas and realize adequate security in future fifth-generation networks, this paper studies physical-layer security in the downlink of a two-tier ultra dense heterogeneous network, where a ubiquitous array formed by ultra dense deployed small-cells surrounds a macrocell base station. In this paper, the locations of legitimate users and eavesdroppers are drawn from Poisson point processes. Then, the cumulative distribution functions of the receive signal-to-interference-plus-noise ratio for legitimate users and eavesdroppers are derived. Further, the average secrecy rate and secrecy coverage probability for each tier as well as for the whole network are investigated. Finally, we analyze the influences on secrecy performance caused by eavesdropper density, transmit power allocation ratio, antenna number allocation ratio, and association area radius.
Yasumasa NAKA Kyohei YAMAMOTO Takuma NAKATA Masaya TAMURA
This paper focuses on underwater wireless power transfer with electric coupling. First, the maximum available efficiency is derived by using the S-parameters of the parallel plate coupler. The frequency which represents the maximal value of the efficiency is revealed. Further, the elevation in the efficiency in association with a reduction of the electrode size is found. It is clarified that the elevation depends on the characteristic of the water dielectric loss. From these results, the optimal electrode size that obtains the maximal value of the efficiency is provided. Finally, we fabricate the couplers by utilizing the optimal frequency and the electrode size. The efficiency of 75.8% under water is achieved.
Kouhei SUZUKI Hideya SO Daisuke GOTO Yoshinori SUZUKI Fumihiro YAMASHITA Katsuya NAKAHIRA Kiyoshi KOBAYASHI Takatoshi SUGIYAMA
This paper introduces distributed array antenna (DAA) systems that offer high antenna gain. A DAA consists of several small antennas with improved antenna gain. This paper proposes a technique that suppresses the off-axis undesired radiation and compensates the time delay by combining signal processing with optimization of array element positioning. It suppresses the undesired radiation by compensating the delay timing with high accuracy and deliberately generating the inter-symbol interference (ISI) in side-lobe directions. Computer simulations show its effective suppression of the equivalent isotropic radiated power (EIRP) pattern and its excellent BER performance.
Ruipan YANG Ruihu LI Luobin GUO Qiang FU
Locally repairable code (LRC) can recover any codeword symbol failure by accessing a small number of other symbols, which can increase the efficiency during the repair process. In a distributed storage system with locally repairable codes, any node failure can be rebuilt by accessing other fixed nodes. It is a promising prospect for the application of LRC. In this paper, some methods of constructing matrices which can generate codes with small locality will be proposed firstly. By analyzing the parameters, we construct the generator matrices of the best-known ternary linear codes of dimension 6, using methods such as shortening, puncturing and expansion. After analyzing the linear dependence of the column vectors in the generator matrices above, we find out the locality of the codes they generate. Many codes with small locality have been found.
Kei SAKAGUCHI Thomas HAUSTEIN Sergio BARBAROSSA Emilio Calvanese STRINATI Antonio CLEMENTE Giuseppe DESTINO Aarno PÄRSSINEN Ilgyu KIM Heesang CHUNG Junhyeong KIM Wilhelm KEUSGEN Richard J. WEILER Koji TAKINAMI Elena CECI Ali SADRI Liang XIAN Alexander MALTSEV Gia Khanh TRAN Hiroaki OGAWA Kim MAHLER Robert W. HEATH Jr.
Wireless engineers and business planners commonly raise the question on where, when, and how millimeter-wave (mmWave) will be used in 5G and beyond. Since the next generation network is not just a new radio access standard, but also an integration of networks for vertical markets with diverse applications, answers to the question depend on scenarios and use cases to be deployed. This paper gives four 5G mmWave deployment examples and describes in chronological order the scenarios and use cases of their probable deployment, including expected system architectures and hardware prototypes. The first example is a 28 GHz outdoor backhauling for fixed wireless access and moving hotspots, which will be demonstrated at the PyeongChang Winter Olympic Games in 2018. The second deployment example is a 60 GHz unlicensed indoor access system at the Tokyo-Narita airport, which is combined with Mobile Edge Computing (MEC) to enable ultra-high speed content download with low latency. The third example is mmWave mesh network to be used as a micro Radio Access Network (µ-RAN), for cost-effective backhauling of small-cell Base Stations (BSs) in dense urban scenarios. The last example is mmWave based Vehicular-to-Vehicular (V2V) and Vehicular-to-Everything (V2X) communications system, which enables automated driving by exchanging High Definition (HD) dynamic map information between cars and Roadside Units (RSUs). For 5G and beyond, mmWave and MEC will play important roles for a diverse set of applications that require both ultra-high data rate and low latency communications.
Ioannis MOSCHOLIOS Michael LOGOTHETIS Shigeo SHIODA
We consider a multirate loss system that accommodates several service-classes with cooperative and non-cooperative users, which generate random or quasi-random arriving calls (depending on the users population). The term “ cooperative” refers to users that can retry (with a certain probability, when the total occupied bandwidth of the system is below a predefined threshold) to be connected in the system with a reduced bandwidth, if they are blocked with their initial peak-bandwidth requirement. This behavior increases the quality of service (QoS) perceived by other users. Due to the retries, the system model does not have a product form solution for the steady state distribution. However, we propose an efficient calculation of system's occupancy distribution, congestion probabilities and system's utilization, while avoiding complex state space enumeration and processing. As it is shown through simulation, the proposed recursive formulas are consistent and quite accurate. For evaluation, we use the conventional trunk/bandwidth reservation control to equalize the congestion probabilities and compare them with the results of the proposed models. Besides, we generalize the proposed models by considering the coexistence of random and quasi-random arrivals. Furthermore, we propose (a) a heuristic method for the determination of desired retry probabilities according to a fairness index and (b) an optimization procedure whereby we assess the retry threshold so that the QoS of the least speed non-cooperative calls is guaranteed for certain retry probabilities of cooperative calls.
Tatsuaki KIMURA Keisuke ISHIBASHI Tatsuya MORI Hiroshi SAWADA Tsuyoshi TOYONO Ken NISHIMATSU Akio WATANABE Akihiro SHIMODA Kohei SHIOMOTO
Network equipment, such as routers, switches, and RADIUS servers, generate various log messages induced by network events such as hardware failures and protocol flaps. In large production networks, analyzing the log messages is crucial for diagnosing network anomalies; however, it has become challenging due to the following two reasons. First, the log messages are composed of unstructured text messages generated in accordance with vendor-specific rules. Second, network events that induce the log messages span several geographical locations, network layers, protocols, and services. We developed a method to tackle these obstacles consisting of two techniques: statistical template extraction (STE) and log tensor factorization (LTF). The former leverages a statistical clustering technique to automatically extract primary templates from unstructured log messages. The latter builds a statistical model that collects spatial-temporal patterns of log messages. Such spatial-temporal patterns provide useful insights into understanding the impact and patterns of hidden network events. We evaluate our techniques using a massive amount of network log messages collected from a large operating network and confirm that our model fits the data well. We also investigate several case studies that validate the usefulness of our method.
Maki ARAI Masashi IWABUCHI Kei SAKAGUCHI Kiyomichi ARAKI
This paper proposes a new methodology to design optimal antennas for MIMO (Multi-Input Multi-Output) communication systems by using spherical mode expansion. Given spatial channel properties of a MIMO channel, such as the angular profile at both sides, the optimal MIMO antennas should provide the largest channel capacity with a constraint of the limited implementation space (volume). In designing a conventional MIMO antenna, first the antenna structure (current distribution) is determined, second antenna directivity is calculated based on the current distribution, and thirdly MIMO channel capacity is calculated by using given angular profiles and obtained antenna directivity. This process is repeated by adjusting the antenna structure until the performance satisfies a predefined threshold. To the contrary, this paper solves the optimization problem analytically and finally gives near optimal antenna structure (current distribution) without any greedy search. In the proposed process, first the optimal directivity of MIMO antennas is derived by applying spherical mode expansion to the angular profiles, and second a far-near field conversion is applied on the derived optimal directivity to achieve near optimal current distributions on a limited surface. The effectiveness of the proposed design methodology is validated via numerical calculation of MIMO channel capacity as in the conventional design method while giving near optimal current distribution with constraint of an antenna structure derived from proposed methodology.
Koh UEDA Yojiro MORI Hiroshi HASEGAWA Hiroyuki MATSUURA Kiyo ISHII Haruhiko KUWATSUKA Shu NAMIKI Toshio WATANABE Ken-ichi SATO
This paper presents a fast and large-scale optical circuit-switch architecture for intra-datacenter applications that uses a combination of space switches and wavelength-routing switches are utilized. A 1,440 × 1,440 optical switch is designed with a fast-tunable laser, 8×8 delivery-and-coupling switch, and a 180×180 wavelength-routing switch. We test the bit-error-ratio characteristics of all ports of the wavelength-routing switch using 180-wavelength 10-Gbps signals in the full C-band. The worst switching time, 498 microseconds, is confirmed and all bit-error ratios are acceptable.
Jae-Yoon JUNG Gyunyoung HEO Kyuhyup OH
Smart card payment systems provide a convenient billing mechanism for public transportation providers and passengers. In this paper, a smart card-based transit log is used to reveal functionally related regions in a city, which are called zones. To discover significant zones based on the transit log data, two algorithms, minimum spanning trees and agglomerative hierarchical clustering, are extended by considering the additional factors of geographical distance and adjacency. The hierarchical spatial geocoding system, called Geohash, is adopted to merge nearby bus stops to a region before zone discovery. We identify different urban zones that contain functionally interrelated regions based on passenger trip data stored in the smart card-based transit log by manipulating the level of abstraction and the adjustment parameters.
Shan DING Gang ZENG Ryo KURACHI Ruifeng HUANG
As a next-generation CAN (Controller Area Network), CAN FD (CAN with flexible data rate) has attracted much attention recently. However, how to use the improved bus bandwidth efficiently in CAN FD is still an issue. Contrasting with existing methods using greedy approximate algorithms, this paper proposes a genetic algorithm for CAN FD frame packing. It tries to minimize the bandwidth utilization by considering the different periods of signals when packing them in the same frame. Moreover, it also checks the schedulability of packed frames to guarantee the real-time constraints of each frame and proposed a merging algorithm to improve the schedulability for signal set with high bus load. Experimental results validate that the proposed algorithm can achieve significantly less bandwidth utilization and improved schedulability than existing methods for a given set of signals.
Junlin TANG Kaida XU Yuan ZENG Guangrong YUE Shaoqian LI
Beamforming technology is an effective method to build a robust link. The commonly used digital beamforming is an expensive and power consuming approach to realizing millimeter-wave transmission. This makes radio frequency(RF) beamforming, which has low cost and low power consumption due to its use of phase shifters the more feasible approach to creating stable links in the millimeter-wave band. Unfortunately, the performance of RF processing is degraded by the limited precision of digital phase shifters. In this paper, we analyze the gain loss caused by the limited precision of phase shifter in millimeter wave single stream beam steering. We deduce a theoretical relationship between the array gain loss and variance of phase error. The theoretical results are validated by the Monte Carlo simulations, which indicate that gain loss could be reduced by the increased precision of phase shifter. In practical applications, 4-bit phase shifters provide sufficient accuracy for single stream beam steering.
Seiji OKAMOTO Kazushige YONENAGA Kengo HORIKOSHI Mitsuteru YOSHIDA Yutaka MIYAMOTO Masahito TOMIZAWA Takeshi OKAMOTO Hidemi NOGUCHI Jun-ichi ABE Junichiro MATSUI Hisao NAKASHIMA Yuichi AKIYAMA Takeshi HOSHIDA Hiroshi ONAKA Kenya SUGIHARA Soichiro KAMETANI Kazuo KUBO Takashi SUGIHARA
We describe a field experiment of flexible modulation format adaptation on a real-time 400Gbit/s/ch DSP-LSI. This real-time DSP-LSI features OSNR estimation, practical simplified back propagation, and high gain soft-decision forward error correction. With these techniques, we have successfully demonstrated modulation format allocation and transmission of 56-channel 400Gbit/s-2SC-PDM-16QAM and 200Gbit/s-2SC-PDM-QPSK signals in 216km and 3246km standard single mode fiber, respectively.
Thomas WILHELEM Hiroyuki OKUDA Tatsuya SUZUKI
This paper presents a novel identification method for hybrid dynamical system models, where parameters have stochastic and time-varying characteristics. The proposed parameter identification scheme is based on a modified implementation of particle filtering, together with a time-smoothing technique. Parameters of the identified model are considered as time-varying random variables. Parameters are identified independently at each time step, using the Bayesian inference implemented as an iterative particle filtering method. Parameters time dynamics are smoothed using a distribution based moving average technique. Modes of the hybrid system model are handled independently, allowing any type of nonlinear piecewise model to be identified. The proposed identification scheme has low computation burden, and it can be implemented for online use. Effectiveness of the scheme is verified by numerical experiments, and an application of the method is proposed: analysis of driving behavior through identified time-varying parameters.
Takahiro OGAWA Akira TANAKA Miki HASEYAMA
A Wiener-based inpainting quality prediction method is presented in this paper. The proposed method is the first method that can predict inpainting quality both before and after the intensities have become missing even if their inpainting methods are unknown. Thus, when the target image does not include any missing areas, the proposed method estimates the importance of intensities for all pixels, and then we can know which areas should not be removed. Interestingly, since this measure can be also derived in the same manner for its corrupted image already including missing areas, the expected difficulty in reconstruction of these missing pixels is predicted, i.e., we can know which missing areas can be successfully reconstructed. The proposed method focuses on expected errors derived from the Wiener filter, which enables least-squares reconstruction, to predict the inpainting quality. The greatest advantage of the proposed method is that the same inpainting quality prediction scheme can be used in the above two different situations, and their results have common trends. Experimental results show that the inpainting quality predicted by the proposed method can be successfully used as a universal quality measure.
Multichannel speech enhancement systems (MSES') have been widely utilized for diverse types of speech interface applications. A state-of-the-art MSES primarily utilizes multichannel minima-controlled recursive averaging for noise estimations and a parameterized multichannel Wiener filter for noise reduction. Many MSES' are implemented in the frequency domain, but they are computationally burdensome due to the numerous complex matrix operations involved. In this paper, a novel MSES intended to reduce the computational complexity with improved performance is proposed. The proposed system is implemented in the mel-filterbank domain using a frequency-averaging technique. Through a performance evaluation, it is verified that the proposed mel-filterbank MSES achieves improvements in the perceptual speech quality with a reduced level of computation compared to a conventional MSES.