Hiroyuki Morikawa

Hiroyuki Morikawa
The University of Tokyo | Todai

About

381
Publications
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2,408
Citations

Publications

Publications (381)
Article
This study solves the magnetic energy minimization problem in inductive power transfer systems to suppress the magnetic field intensity and formulate the lowest boundary of the magnetic energy. The theoretical analysis shows that the minimum value of the magnetic energy is a function only of the coupling coefficient, quality factor of a receiver, a...
Article
In inductive power transfer systems, a transmitter array can maintain high power transfer efficiency (PTE), despite lateral misalignment between the transmitter and receiver. However, a control method for reducing magnetic field leakage in this situation has not been found. Therefore, a novel theory of controlling the transmitter array is necessary...
Conference Paper
In producing oil and gas wells, two-phase flow of gas and liquid is inevitable. Gas density is lighter than liquid density, as a result, gas travels faster than liquid, leaving the liquid phase to build up in pipe segments. The amount of liquid occupying each pipe segment varies. This phenomenon is called liquid holdup, which is defined as the rati...
Article
This paper models and analyzes the power efficiency of wireless power transfer systems with arbitrary load impedances using passive two-port network parameters. In this formulation, two novel indices--the load resistance optimization factor and the load reactance optimization factor--are defined and introduced to indicate the deviation of the load...
Conference Paper
Accurate prediction of the Pressure-Volume-Temperature (PVT) properties of crude oils is required in the reservoir engineering studies and in improving the strategies of the oilfield development. For the past decade, machine learning has been successfully competing with the expensive and time-consuming experimental determination and the limited emp...
Article
The cloud computing market is rapidly expanding and changing the nature of ICT across all sectors; cloud computing transforms ICT from a tool dependent upon investment and physical ownership to one that can easily make use of outside resources. On the other hand, cloud computing services are being provided not only for simple data storage, but for...
Article
LED-to-camera communication for smartphones promises to enable low-cost, small-size, and intuitive data access to Internet-of-things (IoT) devices. However, for fast and reliable communication under the rolling shutter effect, the packet losses caused by inter-frame gaps and frame drops must be dealt with. In this paper, we introduce LED-to-camera...
Article
LoRa is a low-power long-range IoT standard that uses the chirp spread spectrum (CSS) technique, and we have strived to further extend its coverage by utilizing direct Device-to-Device (D2D) links to construct a multi-hop relay network. In LoRa, the spreading factor (SF) is an important parameter, which not only provides great flexibility between t...
Article
To address the open and diverse situation of future optical networks, it is necessary to find a methodology to accurately estimate the value of a target quantity in an optical performance monitor (OPM) depending on the high-level monitoring objectives declared by the network operator. Using machine learning techniques partially enables a trainable...
Conference Paper
Machine learning has been successfully implemented for the past 20 years in estimating reservoir fluid properties competing with the empirical correlations. One of the most commonly utilized modelling schemes is the artificial neural network which is known for its black-box problem that does not show the steps taken to reach the final estimation of...
Article
It is necessary to guarantee the operational range of machine learning (ML)-based optical physical-layer monitors (OPMs). To declare high-level monitoring objectives and obtain their values from OPMs, finding a methodology to accurately estimate the value of a target quantity and ensure their operational range is necessary. We introduce a deep neur...
Article
Single-frequency full-duplex wireless communication (SFD) can increase the efficiency of bandwidth utilization by ideally doubling the spectral efficiency. SFD can be achieved by reducing the level of the self-interference between the transmitter (TX) and receiver (RX) to the RX noise floor. This paper describes a novel decoupling structure to incr...
Article
Presence and occupancy detection in residential and office environments is used to predict movement of people, detect intruders and manage electric power consumption. Specifically, we are developing methods to improve demand side electrical power management by reducing electrical power waste in unoccupied spaces. In this work we conduct an extensiv...
Conference Paper
We experimentally demonstrate that a convolutional neural network (CNN) can acquire an accurate OSNR estimation functionality from asynchronously sampled data right after intradyne coherent detection, while the feature selection before the CNN can be omitted.
Article
Real-time and reliable radio communication is essential for wireless control systems (WCS). In WCS, preambles create significant overhead and affect the real-time capability since payloads are typically small. To shorten the preamble transmission time in OFDM systems, previous works have considered adopting either time-direction extrapolation (TDE)...
Article
In this work, we strive to construct an efficient multi-hop network based on the sub-GHz low-power wide-area (LPWA) technology. Specifically, we investigate the combination of LoRa, a physical-layer standard that can provide severalkilometer outdoor coverage, and concurrent transmission (CT), a recently proposed multi-hop protocol that can signific...
Article
Concurrent transmission (CT) is a revolutionary multi-hop protocol that significantly improves the MAC- and network-layer efficiency by allowing synchronized packet collisions. Although its superiority has been empirically verified, there is still a lack of studies on how the receiver survives such packet collisions , particularly in the presence o...
Article
We propose and experimentally demonstrate a proof-of-concept of a programmable optical transceiver that enables simultaneous optimization of multiple programmable parameters (modulation format, symbol rate, power allocation, and FEC) for satisfying throughput, signal quality, and latency requirements. The proposed optical transceiver also accommoda...
Conference Paper
Many researches have shown that concurrent transmission (CT) helps to improve the energy efficiency and latency of 2.4GHz IEEE-802.15.4-based multi-hop networks. However, it has been shown that the success of CT in IEEE 802.15.4 is mainly due to the DSSS. In view of the great potential of long range sub-GHz technologies for future smart meter appli...
Conference Paper
This paper presents an RSSI-based packet combining (PC) scheme to improve the packet reception reliability affected by a beat interference in wireless sensor networks (WSN) using concurrent transmission (CT). To overcome the beat problem, our PC scheme exploits multiple receptions to perform simple post-detection selection combining based on RSSI v...
Conference Paper
A deep neural network (DNN) is employed for optical performance monitoring. We show that DNN-based monitor successfully estimates OSNR of signals modulated in different formats and symbol rates in the presence of chromatic dispersion and polarization rotation without prior knowledge.
Conference Paper
Positions of sensor nodes are essential information for many UbiComp applications. In this demo, we present an accurate but low-cost 3D localization system based on audible sound. By utilizing the tiny-size MEMS microphone and the high accuracy, lightweight synchronization technology enabled by concurrent transmission flooding (CTF), we developed a...
Conference Paper
We demonstrate a use of deep neural networks (DNN) for OSNR monitoring with minimum prior knowledge. By using 5-layers DNN trained with 400,000 samples, the DNN successfully estimates OSNR in a 16-GBd DP-QPSK system.
Conference Paper
We present a communication protocol called Choco, which efficiently supports various traffic demands with end-to-end reliability in multi-hop Wireless Sensor Networks (WSNs). To achieve this, Choco uses fine-grained scheduling based on the insight that acknowledgements (ACKs) between ends can be delivered with little overhead using concurrent trans...
Conference Paper
In order to provide connectivity for various M2M devices in an easy and cost-effective manner, we propose the concept of "multi-service shared M2M area networks," which enables multiple M2M service providers to commonly use shared M2M gateways. The characteristics of M2M communications are analyzed in this paper based on various M2M use cases, and...
Conference Paper
The overload of Random Access Channel (RACH) has been always considered as one of the largest obstacles to accommodate massive Machine-to-Machine (M2M) devices. While several congestion control mechanisms have been proposed to alleviate the RACH overload, increasing the number of Random Access (RA) slots and/or RACH preamble signatures is considere...
Conference Paper
In LTE-Advanced, a device which tries to connect to a basestation randomly selects one signature from predefined 64 signatures as a device ID, known as a preamble, and transmits it over Random Access Channel (RACH). Those preambles collide to each other when multiple devices transmit the same preamble over the same random access (RA) slot, which le...
Conference Paper
Single-frequency full-duplex wireless communication (SFD) can increase the efficiency of bandwidth utilization. SFD can be achieved by reducing the level of the self-interference between the transmitter (TX) and receiver (RX) to the RX noise floor. In this paper, a full-duplex planar antenna array with high isolation between omnidirectional dipole...
Article
The use of wireless sensor networks for long span bridge monitoring has been expected to remove large portions of sensor installation cost and time. However, the large size of such structures poses difficulties. The communication distances are oftentimes shorter than the bridge scale. Elaborated plans on RF transmission and installation locations a...
Article
This paper proposes a method for measuring the rapidly varying parameters of a power amplifier (PA) characterized by a memory polynomial model in less time than in the symbol period of the orthogonal frequency-division multiplexing (OFDM) signal of a long-term evolution-advanced (LTE-Advanced) system. The method fulfills the dual-updating scheme th...
Article
This paper describes the details of the iteration process used to determine the transfer functions of linear time-invariant (LTI) circuits causing the memory effect of power amplifier (PA). An outline of the method is reported in our work presented at ICCS2012. The accuracy of the method is improved by using cross-correlation spectra at three signa...
Article
Geofencing technology enables various location-based applications by detecting entrance to a predefined region and utilizes the event as a trigger to automatic communication or control of smart devices. In this paper, we implement the proposed geofencing system on Android based smartphone and evaluate performance through field trials. The system is...
Conference Paper
This paper presents how carrier frequency differences among transmitters affect concurrent transmission in wireless sensor networks. The carrier frequency differences cause two problems: reverse phase rotation and signal level fluctuations. The effects of these problems depend on modulation schemes. The demonstration shows these problems with movin...
Conference Paper
This paper presents a system design and experimental eval-uations for ambient sound-based proximity detection with smartphones. Ambient sound is useful as spatiotemporal identi�er. This is because ambient sound contains abundant information which depends on time and space. To detect proximity at high accuracy, we calculate cross correlation in freq...
Conference Paper
Leaf Area Index (LAI) is one of indicators in observing plant growth. Continuous estimation of LAI can increase productivity of agriculture. Since LAI has high correlation with light transmittance into under-foliage, monitoring light transmittance makes it possible to estimate LAI continuously. In this paper, we present a design, implementation, an...
Conference Paper
The objective of this research is to realize a method that detects a user's entrance to predefined geographic area so that appropriate services are provided without explicit user action. Though such geofencing technology is gathering attention due to its wide range of applications, it is a challenge to overcome trade-off between power consumption a...
Conference Paper
Collecting real-world information is an important task for humanitarian applications. To alleviate this cumbersome task, we have presented Choco, a low-power, end-to-end reliable collection protocol for wireless sensor networks. Sensor nodes with Choco can construct multi-hop wireless networks without awareness of network topology thanks to simulta...
Conference Paper
Wireless sensor networks generate big-data which leads to overwhelming traffic in the networks. Compressed sensing (CS) can exploit signal sparsity to reduce the amount of traffic. We evaluate the performance of 1-bit CS with a circulant random bipolar measurement matrix. The results show that 1-bit CS can decrease traffic at higher degree in wirel...
Conference Paper
TDMA is more suitable for high throughput data collection than CSMA. Yet, in wireless sensor network plain TDMA-based protocols require complex scheduling. In case of node failures, plain TDMA is hard to recover connection and achieve robust data collection due to the complex scheduling burden. Toward robust data collection, it is important to deve...
Conference Paper
We present a high throughput data gathering protocol for wireless sensor network. Different from existing works we elaborate a token-scheduled multi-channel TDMA protocol named TKN-TWN that provides better scalability and topology adaptability. TDMA is more suitable for high throughput data collection than CSMA. However, TDMA-based protocols requir...
Conference Paper
We present a design and evaluation of Choco, a low-power, end- to-end reliable collection protocol for wireless sensor networks. We construct Choco on Glossy, which is a recently presented efficient flooding scheme exploiting constructive-interference phenomena. Although Glossy is originally developed for flooding, it can be regarded as a networkin...
Conference Paper
To reduce the complexity of scheduling while exploiting the advantages of TDMA-based data collection, we propose TKN-TWN, a token-scheduled multi-channel data collection protocol. The TKN-TWN uses two tokens to arbitrate data-packet transmissions and associates the ownership of tokens with transmission slot assignment. For the reduction of scheduli...
Conference Paper
This paper presents a preambleless communication system to realize industrial wireless control networks (WCN) which are characterized by short payloads and strict real-time requirements. The reduction of the preamble is greatly beneficial for the real-time operation because the transmission time of preambles is longer than that of the short payload...
Conference Paper
Full-text available
The present paper introduces a power service discovery system. The power service discovery system realizes new power services on a smart grid. The new power services are based on the selection of generations, which enables us to provide/receive electricity under specific conditions. We describe the design and implementation of the power service dis...
Conference Paper
Data-intensive wireless sensor network applications, such as structural health monitoring and earthquake monitoring, require high throughput bulk data collection. Based on the fact that each node stores the same amount of sensor data, we propose a Maximum-Subtree-First Collection Protocol (MSFCP), which adopts Maximum-Subtree-First scheduling on to...
Article
We study the properties of information dissemination over location-aware gossiping networks leveraging location-based real-time communication applications. Gossiping is a promising method for quickly disseminating messages in a large-scale system, but in its application to information dissemination for location-aware applications, it is important t...
Article
For the efficient use of spectrum resource, it is important to understand spectrum occupancy at a high spatial resolution, so a large number of measurement locations are required. In this work, in order to increase measurement locations, we design and implement a low-end spectrum sensor which is capable of switching to different channels in a spect...
Article
Full-text available
The paper shows a compact hard real-time operating system for wireless sensor nodes called PAVENET OS. PAVENET OS provides hybrid multithreading: preemptive multithreading and cooperative multithreading. Both of the multithreading are optimized for two kinds of tasks on wireless sensor networks, and those are real-time tasks and best-effort ones. P...
Article
We present a fast algorithm for probabilistically extracting significant locations from raw GPS data based on data point density. Extracting significant locations from raw GPS data is the first essential step of algorithms designed for location-aware applications. Most current algorithms compare spatial/temporal variables with given fixed threshold...
Conference Paper
Full-text available
A suitable spectrum policy is essential to allow efficient use of the radio spectrum. The Japanese government currently employs a Command and Control (C&C) regime, but measures must be taken to speed up governmental decisions. The first step is to obtain spectrum utilization data which can form the basis of such decisions. This paper describes the...
Conference Paper
We study a network structure for efficient infor- mation dissemination that leverages location-based real-time applications operating in a distributed system. Gossip-based information dissemination is a promising method for a large- scale system to keep nodes in the network quickly updated with new information. The information dissemination efficie...
Conference Paper
Self-* properties have received considerable attention in the literature, and a wide variety of schemes have been proposed recently. In this survey, we introduce the fundamentals of self-stabilizing algorithm development in a highly dynamic environment. Roughly speaking, a self-stabilizing system recovers from recurrent transient faults that distur...
Conference Paper
Full-text available
This paper describes the design, implementation, and evaluation of DLNA Probe, a system for logging the operation histories of Digital Living Network Alliance (DLNA) devices. This paper first describes the combined use of Address Resolution Protocol (ARP) spoofing and the Simple Service Discovery Protocol (SSDP), which obtains the operation histori...
Article
Full-text available
A ubiquitous networking server that enables cross-device as well as cross-network mobility with a location sensing system for context-aware seamless network services is introduced. The context includes the user's presence, position of the user and neighboring devices, network interfaces at-tached to the mobile terminal, availability and available b...
Article
We apply our proposed packet multiplexing mechanism with BGP flow aggregation to asynchronous OPS networks and evaluate packet loss ratio in a FDL buffer through simulation based on real traffic trace data.
Conference Paper
Full-text available
We present a wake-up wireless communication system, which can drastically reduce idle listening energy for long idle listening applications by using a wake-up wireless module. We consider chance encounter communication, which is communication during opportunistic encounters, as a long idle listening application. There are three requirements for app...
Conference Paper
With the development of DLNA technology, more and more DLNA devices appear in our lives. We can extract users' activity events from the operation history of DLNA devices, and provide various services based on them. In this paper, we discuss how to detect anomalous events from operation history of DLNA devices. As the basic technology, we first prop...
Conference Paper
Full-text available
Power consumption in office networks has become a major issue due to its running cost. In order to reduce the power consumption, several approaches have been proposed such as Energy Efficient Ethernet (EEE) and Energy Efficient Wireless aggregation (EEW). In this research, we develop an analytical model and apply the model to evaluate and compare p...
Article
Full-text available
Power conservation has become a serious concern during people's daily life. Ubiquitous computing technologies clearly provide a potential way to help us realizing a more environment-friendly lifestyle. In this paper, we propose a ubiquitous power management system called Gynapse, which uses multi-modal sensors to predict the exact usage of each dev...
Chapter
In order to increase the time connected to already deployed 802.11 wireless networks while traveling by subway in Tokyo, we have developed a system equipped with two scanning modes: 1) passively scanning on a selected channel, and 2) scanning with multiple open authentication. Through analysis and experiments, we have shown that our method increase...
Article
Full-text available
We design a hybrid optical add/drop node combining Multi-Wavelength Optical Packet and Optical Switching for Metro-Area Ring Networks. The feasibility of hybrid switching has been confirmed at a 120 Gb/s network testbed.
Article
Using newly developed PLZT-based OBS core node, low-loss Ether-frame transmission with application-layer connectivity is demonstrated over 92-km 2-hop field testbed. Recent progresses in developing OPS/OCS hybrid router are also reviewed.
Conference Paper
Full-text available
Abstract- In this paper, we propose a power saving mechanism based on a simple moving average of the traffic rate in 802.3ad link aggregation. Two key components comprise the proposed mechanism: (1) a negotiation protocol for both nodes connected to an 802.3ad aggregated link and (2) an algorithm to estimate an appropriate number of active links to...
Article
This paper proposes significant route identification; the concept is to combine the locations acquired by the GPS module of the user's cellular phone. Significant routes are those that the user most frequently passes along. The proposal overcomes the two main weaknesses of cellular phones. One is that GPS data is acquired infrequently in order to r...