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Author

Kenichi Takizawa

Other affiliations: Niigata University, Aalto University
Bio: Kenichi Takizawa is an academic researcher from National Institute of Information and Communications Technology. The author has contributed to research in topics: Wireless & Communication channel. The author has an hindex of 17, co-authored 154 publications receiving 1348 citations. Previous affiliations of Kenichi Takizawa include Niigata University & Aalto University.


Papers
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Journal ArticleDOI
TL;DR: This article outlines some of the research that has been done to obtain accurate propagation models supporting the standardization of implant communication in BANs and current research to enhance the channel models of IEEE Std 802.15.6.
Abstract: A body area network is a radio communication protocol for short-range, low-power, and highly reliable wireless communication for use on the surface, inside, or in the peripheral proximity of the human body Combined with various biomedical sensors, BANs enable realtime collection and monitoring of physiological signals Therefore, it is regarded as an important technology for the treatment and prevention of chronic diseases, and health monitoring of the elderly The IEEE 802 LAN/MAN Standards Committee approved Task Group TG156 in December 2007 As a result of more than four years of effort, in February 2012, TG156 published the first international standard for BANs, IEEE Std 802156 Throughout the development of this standard, ample collaboration between the standardization group and the research community was required In particular, understanding the radio propagation mechanisms for BANs demanded the most research effort Technical challenges were magnified for the case of implant communication because of the impossibility of conducting in-body measurements with human subjects Therefore, research in this field had to make use of intricate computer simulations This article outlines some of the research that has been done to obtain accurate propagation models supporting the standardization of implant communication in BANs Current research to enhance the channel models of IEEE Std 802156 through the use of ultra wideband signals for implantable devices along with physical measurements in animals is also presented

127 citations

Journal ArticleDOI
TL;DR: A new multichannel neural recording system that can record up to 4096-channel electrocorticogram data by multiple connections of customized application-specific integrated circuits (ASICs) and an ultra-wideband wireless unit for transmitting the recorded neural signals.
Abstract: Simultaneous recordings of neural activity at large scale, in the long term and under bio-safety conditions, can provide essential data. These data can be used to advance the technology for brain-machine interfaces in clinical applications, and to understand brain function. For this purpose, we present a new multichannel neural recording system that can record up to 4096-channel (ch) electrocorticogram data by multiple connections of customized application-specific integrated circuits (ASICs). The ASIC includes 64-ch low-noise amplifiers, analog time-division multiplexers, and 12-bit successive approximation register ADCs. Recorded data sampled at a rate of 1 kS/s are multiplexed with time division via an integrated multiplex board, and in total 51.2 Mbps of raw data for 4096 ch are generated. This system has an ultra-wideband (UWB) wireless unit for transmitting the recorded neural signals. The ASICs, multiplex boards, and UWB transmitter unit are designed with the aim of implanting them. From preliminary experiments with a human body-equivalent liquid phantom, we confirmed 4096-ch UWB wireless data transmission at 128 Mbps for distances below 20 mm .

81 citations

Journal ArticleDOI
TL;DR: In this paper, ground-to-satellite laser communication experiments between the optical ground station located in Koganei, central Tokyo, and a low earth orbit (LEO) satellite were jointly performed by the Japan Aerospace Exploration Agency and the National Institute of Information and Communications Technology.
Abstract: Ground-to-satellite laser communication experiments between the optical ground station located in Koganei, central Tokyo, and a low earth orbit (LEO) satellite were jointly performed by the Japan Aerospace Exploration Agency and the National Institute of Information and Communications Technology. In 18 trials during three non-consecutive months, the satellite was acquired and tracked 61 % of the time, when clear or partly-clear conditions were predominant. The optical link was maintained for about 6 minutes when the satellite was visible in spite of the high angular velocity of the satellite. In 3 of the 18 trials, the link was not interrupted due to clouds during the six-minute transit. The failures (39% of the time) occurred when cloudy or rainy conditions were predominant. Fluctuation in the uplink received signal power was minimized by using multiple laser beam transmissions. The measured uplink and downlink bit error ratios were 10-7-10-4. These results demonstrate the applicability of free-space laser communication for not only geostationary earth orbit-LEO optical links but also ground-to-LEO optical links.

74 citations

Proceedings ArticleDOI
17 Oct 2008
TL;DR: This invited paper introduces a progress of research and development of body area network, i.e. BAN and its standardization in IEEE802.15.6 in a field of medical ICT in order to encourage global collaboration as well as planting many R&D and business seeds in academia and industry.
Abstract: A new major application of UWB is medical healthcare using advantages of low power spectrum density, high capacity of transmission and accurate ranging. As a core network of medical healthcare based on ICT, i.e. medical ICT, a body area network (BAN) has been researched and developed. BAN can provide a wide range of applications in primary for medical healthcare such as tele-metering vital sign, e.g. ECG, EEG, tele-controlling medical equipment, e.g. capsule endoscope and in addition for non-medical service such as entertainment. To harmonize with the strong demands from both medical healthcare societies and ICT industries, a standardization committee referred to as IEEE 802.15.6 was formally set up in December 2007. The objective of 15.6 is to define new physical (PHY) and media access control (MAC) layers for wireless BAN (WBAN). This invited paper introduces a progress of research and development of body area network, i.e. BAN and its standardization in IEEE802.15.6 in a field of medical ICT in order to encourage global collaboration as well as planting many R&D and business seeds in academia and industry.

71 citations

Proceedings ArticleDOI
14 Oct 2008
TL;DR: This paper provides stochastic channel models for wireless body area network (WBAN) on the human body by extracting parameters from measured channel transfer functions (CTFs) in a hospital room.
Abstract: Wireless patient monitoring using wearable sensors is a promising application. This paper provides stochastic channel models for wireless body area network (WBAN) on the human body. Parameters of the channel models are extracted from measured channel transfer functions (CTFs) in a hospital room. Measured frequency bands are selected so as to include permissible bands for WBAN; ultra wideband (UWB), the industry, science and medical (ISM) bands, and wireless medical telemetry system (WMTS) bands. As channel models, both a path loss model and a power delay profile (PDP) model are considered. But, even though path loss models are derived for the all frequency bands, PDP model is only for the UWB band due to the highly frequency selectiveness of UWB channels. The parameters extracted from the measurement results are summarized for each channel model.

69 citations


Cited by
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Christopher M. Bishop1
01 Jan 2006
TL;DR: Probability distributions of linear models for regression and classification are given in this article, along with a discussion of combining models and combining models in the context of machine learning and classification.
Abstract: Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

10,141 citations

Journal ArticleDOI
TL;DR: This paper provides a detailed investigation of sensor devices, physical layer, data link layer, and radio technology aspects of BAN research, and presents a taxonomy of B Ban projects that have been introduced/proposed to date.
Abstract: Advances in wireless communication technologies, such as wearable and implantable biosensors, along with recent developments in the embedded computing area are enabling the design, development, and implementation of body area networks. This class of networks is paving the way for the deployment of innovative healthcare monitoring applications. In the past few years, much of the research in the area of body area networks has focused on issues related to wireless sensor designs, sensor miniaturization, low-power sensor circuitry, signal processing, and communications protocols. In this paper, we present an overview of body area networks, and a discussion of BAN communications types and their related issues. We provide a detailed investigation of sensor devices, physical layer, data link layer, and radio technology aspects of BAN research. We also present a taxonomy of BAN projects that have been introduced/proposed to date. Finally, we highlight some of the design challenges and open issues that still need to be addressed to make BANs truly ubiquitous for a wide range of applications.

1,239 citations

Journal ArticleDOI
TL;DR: This survey reports the characteristics and requirements of UAV networks for envisioned civil applications over the period 2000-2015 from a communications and networking viewpoint and elaborate on general networking related requirements such as connectivity, adaptability, safety, privacy, security, and scalability.
Abstract: The days where swarms of unmanned aerial vehicles (UAVs) will occupy our skies are fast approaching due to the introduction of cost-efficient and reliable small aerial vehicles and the increasing demand for use of such vehicles in a plethora of civil applications. Governments and industry alike have been heavily investing in the development of UAVs. As such it is important to understand the characteristics of networks with UAVs to enable the incorporation of multiple, coordinated aerial vehicles into the air traffic in a reliable and safe manner. To this end, this survey reports the characteristics and requirements of UAV networks for envisioned civil applications over the period 2000–2015 from a communications and networking viewpoint. We survey and quantify quality-of-service requirements, network-relevant mission parameters, data requirements, and the minimum data to be transmitted over the network. Furthermore, we elaborate on general networking related requirements such as connectivity, adaptability, safety, privacy, security, and scalability. We also report experimental results from many projects and investigate the suitability of existing communication technologies for supporting reliable aerial networking.

1,067 citations

Journal ArticleDOI
TL;DR: A comprehensive survey of mmWave communications for future mobile networks (5G and beyond) is presented, including an overview of the solution for multiple access and backhauling, followed by the analysis of coverage and connectivity.
Abstract: Millimeter wave (mmWave) communications have recently attracted large research interest, since the huge available bandwidth can potentially lead to the rates of multiple gigabit per second per user Though mmWave can be readily used in stationary scenarios, such as indoor hotspots or backhaul, it is challenging to use mmWave in mobile networks, where the transmitting/receiving nodes may be moving, channels may have a complicated structure, and the coordination among multiple nodes is difficult To fully exploit the high potential rates of mmWave in mobile networks, lots of technical problems must be addressed This paper presents a comprehensive survey of mmWave communications for future mobile networks (5G and beyond) We first summarize the recent channel measurement campaigns and modeling results Then, we discuss in detail recent progresses in multiple input multiple output transceiver design for mmWave communications After that, we provide an overview of the solution for multiple access and backhauling, followed by the analysis of coverage and connectivity Finally, the progresses in the standardization and deployment of mmWave for mobile networks are discussed

887 citations

Journal ArticleDOI
02 Dec 2019
TL;DR: In this article, the authors give a tutorial overview of the recent advances in UAV communications to address the above issues, with an emphasis on how to integrate UAVs into the forthcoming fifth-generation (5G) and future cellular networks.
Abstract: Unmanned aerial vehicles (UAVs) have found numerous applications and are expected to bring fertile business opportunities in the next decade. Among various enabling technologies for UAVs, wireless communication is essential and has drawn significantly growing attention in recent years. Compared to the conventional terrestrial communications, UAVs’ communications face new challenges due to their high altitude above the ground and great flexibility of movement in the 3-D space. Several critical issues arise, including the line-of-sight (LoS) dominant UAV-ground channels and induced strong aerial-terrestrial network interference, the distinct communication quality-of-service (QoS) requirements for UAV control messages versus payload data, the stringent constraints imposed by the size, weight, and power (SWAP) limitations of UAVs, as well as the exploitation of the new design degree of freedom (DoF) brought by the highly controllable 3-D UAV mobility. In this article, we give a tutorial overview of the recent advances in UAV communications to address the above issues, with an emphasis on how to integrate UAVs into the forthcoming fifth-generation (5G) and future cellular networks. In particular, we partition our discussion into two promising research and application frameworks of UAV communications, namely UAV-assisted wireless communications and cellular-connected UAVs, where UAVs are integrated into the network as new aerial communication platforms and users, respectively. Furthermore, we point out promising directions for future research.

761 citations