Publishing type：Research paper (scientific journal)  

In sensor networks, sensor localization is one of the mandatory functions for physical sensing. In this paper, we propose a sensor localization system that utilizes wireless local area network (WLAN) access points (APs) as anchor nodes. WLAN is widely available nowadays, and WLAN APs are used in many environments. Therefore, for our localization system, we utilize the WLAN APs already installed in the environment, thereby eliminating the installation of new anchors. We present an AP received signal strength (RSS) measurement method, which is the key technology of our sensor localization system. Notably, sensor nodes equipped with an IEEE 802.15.4 (ZigBee) module cannot detect WLAN AP signals. We therefore developed an AP signal detection method with AP identification by employing a cross-technology signal detection technique. Experimental evaluations demonstrate that our AP signal detection method successfully identified sender APs with a false positive (FP) detection rate less than 20%. The experiments also validated that the measured AP-RSS followed the same distribution as the RSS measured using a WLAN device.

DOI： 10.18494/SAM.2020.2592

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Vehicle detection is a basic component for many applications in intelligent transportation system (ITS). We are developing a low-cost vehicle detector relying on sound arrival time difference on two microphones. Our previous paper presented that our acoustic vehicle detector successfully detected vehicles with an F-measure of 83 %. However, the acoustic detector has difficulties in vehicle detection in an environment with steady noise such as rain noise.This paper presents a steady-noise suppression method for the acoustic vehicle detector. Our key idea is to exclude the influence of steady noise in a sound delay estimation. The acoustic vehicle detector estimates vehicle sound delay by finding a peak on a cross-correlation function. We theoretically analyze the influence of steady noise and remove a peak caused by the noise to minimize the influence. Experimental evaluations revealed that the steady-noise suppression method effectively reduced the noise influence and resulted in F-measures of 0.92 and 0.90 in normal and heavy rain conditions, respectively.

DOI： 10.1109/ITSC.2019.8917289

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Publishing type：Research paper (scientific journal)   Publisher：{MDPI} {AG}  

DOI： 10.3390/s19071645

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Vehicle detection is one of the fundamental tasks in the ITS (intelligent transport system). We are developing an acoustic vehicle detector that relies on two microphones at a sidewalk [1]. The vehicle detector successfully detected vehicles as well as their traveling directions. However, the detector has difficulties in vehicle detection in a high wind condition due to wind noise. This paper presents a wind noise suppressor for the acoustic vehicle detector. Our simple idea is to remove frequency components corresponding to wind noise. Our acoustic vehicle detector relies on TDOA (time difference of arrival) of sound signals on two microphones to detect vehicles, which can be derived from a part of frequency components of vehicle sound signals. We experimentally analyze frequency components of wind noise and design a filter to reduce wind noise. Initial experimental evaluations revel that our vehicle detector with a wind noise suppressor successfully detected vehicles with an F-measure of 0.77 in a normal wind condition.

DOI： 10.1109/PERCOMW.2019.8730822

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Sensor localization is one of the big problems when building large scale indoor sensor networks. We are developing ZigLoc, a sensor localization system using Wi-Fi (IEEE802.11) APs (access points) as references [1], [2]. ZigLoc measures RSS (received signal strength) of Wi-Fi AP signals to localize ZigBee (IEEE802.15.4) sensor nodes. However, ZigLoc exhibits low accuracy because of inaccurate RSS measured on a single narrow-band ZigBee channel. In this paper, we present a highly accurate sensor localization system MultiZigLoc, which is an extended system of ZigLoc. Our key idea is to employ RSS measured in multiple ZigBee channels in fingerprinting localization. The RSS in multiple channels is dependent on the measured location because ZigBee uses narrow-band channels. Narrow-band ZigBee communication is highly affected by frequency selective fading, whose influence is dependent on channels and locations of both Wi-Fi APs and a sensor. We utilize fingerprints that separately handles RSS in multiple ZigBee channels to employ channel specific features. We conducted initial evaluations using RSS measured in a practical environment. The evaluations reveal that MultiZigLoc improved the localization accuracy by more than 10 points.

DOI： 10.23919/ICMU.2018.8653263

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Kinetic visual acuity (KVA) is one of the essentials in sports vision. Although virtual reality is thought to be a plausible tool for training KVA, it is not clear that the vision training in VR is effective in actual environment beause the focal point length is different. In this paper, the training effect in VR is evaluated in the real environment in the same visual motion task. It is confirmed that the task performance is improved after the training in VR in the medium target speed.</p>

DOI： 10.1299/jsmermd.2019.2P1-O02

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DOI： 10.3390/s19040884

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In the ITS (intelligent transportation system), vehicle detection is one of the core technologies. We are developing an acoustic vehicle detector that detects vehicles using a sound map, which is a map of sound arrival time difference on two microphones. We developed vehicle detection algorithms based on state machine and DTW (dynamic time warping) to detect S-curves on a sound map drawn by passing vehicles. However, the detection algorithms often fail to detect simultaneous and sequential passing vehicles. This paper presents SAVeD, a sequential acoustic vehicle detector. The SAVeD fits an S-curve model to sound map points using a RANSAC (random sample consensus) robust estimation method to detect each vehicle. The SAVeD then removes sound map points corresponding to the detected vehicle and continues vehicle detection process for the following vehicles. Experimental evaluations demonstrated that the SAVeD improves detection accuracy by more than 10 points compared to the state-machine based algorithm.

DOI： 10.1109/ITSC.2018.8569727

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

This paper presents an actual BLE-based indoor localization system utilizing separate channel fingerprinting. Separate channel fingerprinting measures RSS (received signal strength) of BLE signals in three advertising channels to enhance location-specific features for accuracy improvement. The basic ideas of separate channel fingerprinting was presented in our previous work lacking evaluation of localization accuracy in a practical environment. We therefore present design and implementation of a localization system utilizing separate channel fingerprinting. We conducted experimental evaluation and demonstrated that the separate channel fingerprinting successfully improved localization accuracy by approx. 28.5%.

DOI： 10.1109/IIAI-AAI.2018.00032

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Sensor localization is one of the big problems when building large scale indoor sensor networks because GPS (Global Positioning System) is unavailable in indoor environments. We are developing ZigLoc, a sensor localization system using WiFi APs (access points) as references, which requires no additional infrastructure [1,2]. In ZigLoc, a sensor node measures RSS (received signal strength) of WiFi AP signals using a ZigBee (IEEE 802.15.4) module. Location of a sensor node is then estimated using fingerprints collected for a WiFi localization system. However, ZigLoc exhibits low accuracy due to the RSS offset derived by ZigBee and WiFi modules. The RSS offset is mainly caused by the channel bandwidth difference. In this paper, we present a differential fingerprinting method to improve localization accuracy. Our key idea is that we focus on RSS difference between WiFi APs. RSS difference between APs should be the same when we measure RSS using either ZigBee or WiFi modules. Differential fingerprinting only relies on RSS difference in fingerprint similarity calculation. We conducted experimental evaluations in a practical environment. The experimental evaluations reveal that ZigLoc accuracy was improved by approximately 26 % using the differential fingerprinting method.

DOI： 10.23919/ICMU.2017.8330074

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

Smart mobility systems, which include Intelligent Transportation Systems (ITS) and smart energy ones, become more important. There is, however, lack of its platform studies. This paper proposes a sustainable information infrastructure project for smart mobility systems. The project pursues issues that establish an information infrastructure architecture and a seamless development method chain for it. The project has mainly two features: (1) applying life-cycle-oriented methods, which are a cycle from system development phase to operation phase. In addition, these methods are applied to real world applications, and (2) dealing with an uncertainty that occurs in system development upper phase. This paper describes an overview of the project.

DOI： 10.1007/978-3-319-70636-8_3

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/IIAI-AAI.2018.00025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Verlag  

Bluetooth Low Energy (BLE) based localization is a next candidate for indoor localization. In this paper, we propose a new BLE-based fingerprinting localization scheme that improves localization accuracy. BLE is a narrow bandwidth communication that is highly affected by frequency selective fading. Frequency selective fading is mainly caused by multipaths between a transmitter and receiver, which are dependent on channels. We utilize channel specific features by separately measure received signal strength (RSS) on different channels to improve localization accuracy. BLE standards provide no API to retrieve channel information of incoming packets. We therefore developed a separate channel advertising scheme to separately measure RSS on different channels. To demonstrate the feasibility of the separate channel fingerprinting, we conducted preliminary experiments as well as initial evaluations. Experimental evaluations demonstrated that the separate channel fingerprinting improves localization accuracy by approximately 12%.

DOI： 10.1007/978-3-319-70636-8_2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Communications in Computer and Information Science  

We have developed an ad-hoc wireless positioning network (AWPN) to realize on-demand indoor location-based services [10]. This paper extends our AWPN to handle huge number of localization requests. In AWPN, WiFi APs measure received signal strength (RSS) of WiFi signals and send the RSS information to a localization server via a WiFi mesh network. The maximum number of WiFi devices is therefore limited by computational resources on the localization server. We push this limit by introducing a new distributed calculation scheme: we use the MapReduce computation framework and perform map processes on APs and reduce processes on localization servers. We also utilize a network router capable of network address translation (NAT) for shuffle processes to provide scalability. We implemented and evaluated our distributed calculation scheme to demonstrate that our scheme almost evenly distributes localization calculations to multiple localization servers with approximately 26% variations.

DOI： 10.1007/978-3-319-68282-2_3

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Smart mobility systems, which include Intelligent Transportation System (ITS) and smart energy systems, become more important. There is, however, lack of its platform studies. This paper proposes a sustainable information infrastructure project for smart mobility systems. The project pursues issues that establish an information infrastructure architecture and seamless development method chain for it. The project has mainly two features; 1) applying life-cycle-oriented methods, which are a cycle from system development to operations, to the real world, and 2) dealing with uncertainties when a system begins to be designed. This paper describes an overview of the project.

DOI： 10.1109/IIAI-AAI.2016.110

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Sensor localization is one of the big problems when building large scale indoor sensor networks because GPS (Global Positioning System) is unavailable in indoor environments. We are developing a sensor localization system using WiFi APs as anchors, which requires no anchor deployment. Because sensor nodes cannot demodulate WiFi signals, we have developed a cross-technology RSS (received signal strength) measurement scheme with an AP recognition scheme [1, 2].
In this paper, we present WiChest, a WiFi-AP operating channel estimation scheme to accurately measure AP-RSS on sensor nodes. A WiFi channel overlaps with four ZigBee channels. AP-RSS depends on a ZigBee channel in which a sensor node measures the RSS. Using WiChest, a sensor node automatically switches its channel based on an estimated AP channel prior to RSS measurement. We implemented WiChest using a MICAz sensor node. The experimental evaluations reveal that WiChest accurately estimates AP operating channels with an F-measure of 0.80.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a privacy-aware user tracking system which traces users by their footprints. Tracking by footprints could reduce discomfort for privacy-sensitive users compared with the use of face recognition by cameras in existing tracking systems, since a footprint is weakly identifiable personal information, i.e., it cannot directly identify a specific individual. In this context, the proposed system is said to be privacy-aware. In the proposed tracking system, the footprint data are collected from spatially disjoint pressure sensor sheets put on significant locations in a target area. The trajectory of a specific user is estimated by extracting a sequence of sensor sheets that can observe the footprint of the user. The main task to be handled in the system is to recognize correspondence between footprints measured across multiple pressure sensor sheets. Moreover, we have conducted a basic evaluation to confirm the feasibility of the proposed system. The result shows that it can distinguish users by 94%.

DOI： 10.1109/IIAI-AAI.2016.211

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

BLE (Bluetooth Low Energy) based localization is a next candidate for indoor localization. In this paper, we propose a new BLE-based fingerprinting localization scheme that improves localization accuracy. BLE is a narrow band communication that is highly affected by frequency selective fading and channel gains. We employ channel-specific features to location fingerprint to improve localization accuracy. Current BLE standards provide no API to retrieve an advertising channel number. We therefore developed a separate channel advertising scheme to measure RSS (Received Signal Strength) on each advertising channel. To demonstrate the feasibility of the separate channel fingerprinting, we conducted initial evaluations. Experimental evaluations showed that the separate channel fingerprinting improves accuracy by approximately 12 %.

DOI： 10.1109/IIAI-AAI.2016.22

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have developed a privacy-aware user tracking system that can track users by using their footprint data measured across spatially disjoint pressure sensor sheets. The main task in the system is to recognize correspondence between footprints measured across pressure sensor sheets, i.e., it needs to recognize a single user walking across pressure sensor sheets as an instance and different users as different ones. In this paper, we propose a footprint matching method designed for walking users. It mainly consists of two steps: i.e., footprint averaging and similarity calculating, in order to handle footprint data recorded as a time series for a walking user. Moreover, we have conducted a basic evaluation to confirm the effectiveness of the proposed footprint matching method. The result shows that the matching performance can achieve 78%.

DOI： 10.1109/ICA.2016.41

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/HPCC-CSS-ICESS.2015.111

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORPORATION  

Multipoint relays (MPRs) are used for flooding topology control messages and finding the shortest paths for unicast communications in the optimized link state routing protocol (OLSR). In this paper, we propose a method for achieving more efficient MPR selection in moderately dense wireless multihop networks (including sensor networks) than the conventional MPR selection. First, we analyze moderately dense networks to show that a node close to the two-hop border has little probability of being a two-hop neighbor. Second, we explain that there is a chance of the node's MPRs being shared with its neighbors. To maximize this chance, we propose using shared MPR sets. These sets minimize the MPR ratio, which is defined as the number of nodes selected as MPRs by at least one neighbor divided by the total number of nodes in the network. Simulations are used to confirm the efficiency of using shared MPR sets. A centralized heuristic algorithm shows an MPR ratio redundancy in moderately dense networks that is about 10% of that obtained through conventional MPR selection.

DOI： 10.1155/2015/486023

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Sensor localization is one of the big problems when building large scale indoor sensor networks because GPS is unavailable in indoor environments. In this paper, we propose a sensor localization system using WiFi APs as anchors. WiFi APs are largely installed in indoor environments and are managed by a network system manager. Using WiFi APs as anchors, we can localize sensor nodes with neither newly deployed anchor nodes nor user cooperation.
As a first step of our sensor localization system, this paper presents a WiFi AP-RSS monitoring system using sensor nodes. Sensor nodes are equipped with ZigBee (IEEE 802.15.4) modules, which cannot demodulate WiFi (IEEE 802.11) signals. We therefore developed a cross-technology signal extraction scheme with an AP recognition scheme on sensor nodes. We herein describe the design and implementation of our AP-RSS monitoring system. The experimental evaluations demonstrated that the proposed AP-RSS monitoring system successfully recognized WiFi APs with detection errors less than 10 %. We also confirmed that the proposed system monitored AP-RSS with an average error of 1.26 dB.

DOI： 10.1109/CANDAR.2015.54

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Sensor localization is one of the big problems when building large scale indoor sensor networks since GPS is unavailable in indoor environments. Many indoor localization systems have been proposed to tackle the sensor localization problem, yet user cooperation or many anchor nodes are required. In this paper, we propose a sensor localization system using WiFi APs as anchors. WiFi APs are largely installed in indoor environments and are managed by a network system manager. Using WiFi APs as anchors, we can localize sensor nodes without newly deployed anchor nodes.
As a first step of our sensor localization system, this paper presents a WiFi AP-RSS monitoring system using sensor nodes. Sensor nodes are equipped with IEEE 802.15.4 (ZigBee) modules, which cannot demodulate WiFi (IEEE 802.11) signals. We therefore developed a cross-technology signal extraction scheme on sensor nodes. We herein describe the design and implementation of our AP-RSS monitoring system. The experimental evaluations show that our AP-RSS monitoring system successfully retrieves AP-RSS with an average error of 1.26 dB.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

WiFi interference is one of the big problems in ZigBee-based sensor networks. In this paper, we present a new WiFi-ZigBee coexistence scheme named AP-assisted CTS-blocking (AA CTS-blocking). The AA CTS-blocking uses an RTS/CTS (request to send, clear to send) mechanism to prevent WiFi transmissions during ZigBee communications. An RTS/CTS mechanism is defined in the IEEE 802.11 standard and is supported by off-the-shelf WiFi devices. We present the design and implementation of AA CTS-blocking utilizing an off-the-shelf WiFi device as it is. The experimental evaluations revealed that AA CTS-blocking reduced frame error rate (FER) by approximately 5% compared to an existing WiFi-ZigBee coexistence scheme.

DOI： 10.1109/CANDAR.2015.16

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/UIC-ATC-ScalCom.2014.96

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE Computer Society  

In this poster, we introduce our developed wireless tag system called Smart Narrow Field Communication (SNFC). The purpose of SNFC is to provide a long url of the contents on the Internet easily like QR code and NFC (Near Field Communication). SNFC assumes a device name of wireless applications as a tag for recognizing a target content. The relationship between a device name and the url is managed on our cloud system. In addition to a device name, our system takes other user contexts such as gender and age into consideration for deciding the target content. The advantage of SNFC is that all the common devices such as WiFi router or Bluetooth mouse can be used as a tag. © 2014 IEEE.

DOI： 10.1109/ICMU.2014.6799072

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Language：Japanese   Publisher：一般社団法人情報処理学会  

本論文では,スマートフォンに搭載された WiFi や Bluetooth といった通信用の電波を電子タグとして用いるスマート無線タグシステム (SNFC:Smart Narrow Field Communication) の開発について報告する.SNFC では,通信用の電波に割り当てられる識別子や MAC アドレスをタグとして用いることで,低コスト化を図るとともに,認識範囲が約 10〜20m 程度と広くなり,従来の QR コードや NFC と比較して,一度に複数人がタグを読み取れるという利点がある.本発表では,開発した Android 用 SDK,iPhone 用 SDK,並びに WiFi と Bluetooth の両方を発信するタグについて報告する.

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Language：English   Publishing type：Research paper (scientific journal)  

In this paper, we focus on a monitoring environment with wireless sensor network in which multiple mobile sink nodes traverse a given sensing field in different spatial-temporal patterns and collect various types of environmental data with different deadline constraints. For such an environment, we propose an energy-efficient data collection method that reduces intermediate transmission in multi-hop communication while meeting predetermined deadlines. The basic approach of the proposed method is to temporarily gather (or buffer) the observed data into several sensor nodes around the moving path of the mobile sink that would meet their deadlines at the next visit. Then, the buffered data is transferred to the mobile sink node when it visits the buffering nodes. We also propose a mobile sink-initiated proactive routing protocol with low cost (MIPR-LC) that efficiently constructs routes to the buffering nodes on each sensor node. Moreover, we simulate the proposed collection method and routing protocol to show their effectiveness. Our results confirm that the proposed method can gather almost all of the observed data within the deadline, while reducing the intermediate transmissions by 30%, as compared with an existing method. In addition, the MIPR-LC method can reduce the transmissions for the route construction by up to 12% when compared with a simple routing protocol. © 2013 Information Processing Society of Japan.

DOI： 10.2197/ipsjjip.21.320

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DOI： 10.1109/AINA.2013.52

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DOI： 10.1109/WAINA.2013.128

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DOI： 10.1109/AINA.2013.53

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Language：English   Publisher：Information and Media Technologies Editorial Board  

In this paper, we focus on a monitoring environment with wireless sensor network in which multiple mobile sink nodes traverse a given sensing field in different spatial-temporal patterns and collect various types of environmental data with different deadline constraints. For such an environment, we propose an energy-efficient data collection method that reduces intermediate transmission in multi-hop communication while meeting predetermined deadlines. The basic approach of the proposed method is to temporarily gather (or buffer) the observed data into several sensor nodes around the moving path of the mobile sink that would meet their deadlines at the next visit. Then, the buffered data is transferred to the mobile sink node when it visits the buffering nodes. We also propose a mobile sink-initiated proactive routing protocol with low cost (MIPR-LC) that efficiently constructs routes to the buffering nodes on each sensor node. Moreover, we simulate the proposed collection method and routing protocol to show their effectiveness. Our results confirm that the proposed method can gather almost all of the observed data within the deadline, while reducing the intermediate transmissions by 30%, as compared with an existing method. In addition, the MIPR-LC method can reduce the transmissions for the route construction by up to 12% when compared with a simple routing protocol.

DOI： 10.11185/imt.8.585

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Association for Computing Machinery  

This paper proposes a mechanism to share and utilize various sensors among multiple Android terminals for a functional enhancement and a battery life extension. The most important contribution is how to emulate the value from remote sensor as a value from a local sensor. By this emulation, all the other applications existed on Google Play Market can utilize remote sensors without any modification. For realizing our proposal, we modified Android OS itself, and developed two applications that run on Android OS. In the former, we uniquely modified SensorManager of Android OS for supporting an external sensors. In the latter, we made a virtualizing application for each embedded sensors that sends a value to other terminals via Bluetooth. Also, we developed a control application of our function itself. Through our demo using "Penguin Skiing 3D", we show that an acceleration sensor is successfully virtualized and is behaving as a local sensor of another terminal. In addition, we evaluate the affect of a sampling interval and a cache update interval at a remote terminal against the accuracy at a local terminal.

DOI： 10.1145/2517351.2517385

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Intelligent Transportation Society of America  

A car navigation system requires the latest reliable digital road map database for correctly performing responsible tasks, such as map display, positioning, route planning, and route guidance. In fact, however, the pre-installed road map database is used without any updates, although the actual roads were added and/or removed, since there is no easy way to update the database. This would cause misleading behaviors of these tasks. In this paper, we propose a broadcast-based notification protocol to inform car navigation systems about the existence of the updates in the road map database, in order to reduce the misleading influence of updated roads. The results of evaluations conducted on the efficacy of our proposed protocol indicate that it achieves all notifications for updated roads by broadcasting invalidation reports of 478KB, while the total size of the road map database is 132MB.

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WiFiTag is a simple and low cost solution for associating the real world to the online media such as web sites and YouTube. Our idea is to redirect a user's access based on the information of surrounding WiFi access points. Compared with WiFi-based indoor positioning system, our system requires no calculation and no much access points. This is because our system associates the digital content not with the location but with the AP itself. as the information of AP, we use ESSID, BSSID, and RSSI. by uploading a scanned WiFi information to the WiFiTag server, a terminal can get the proper URL as a response. Relationship between the WiFiTag and the URL have been defined ahead. WiFiTag realize "real to virtual" connection easily. for example, by associating lab's SSID to lab's HP, a visitor can access a lab's HP easily and directly, when the visitor comes to our lab. a camera required for QR code don't need for our system. in addition, a special card reader and touch action required for NFC are also unnecessary. If WiFi has already exist, no additional cost is necessary for our system. in this paper, we describe a overall concept of WiFiTag and show the availability and feasibility of our proposed system through some experimental evaluation results. © 2012 IEEE.

DOI： 10.1109/3PGCIC.2012.70

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a dynamic channel assignment method that utilizes location information of mobile terminals to calculate the optimal channel scheme in indoor WLAN positioning systems. Our method could achieve two goals: (a) the optimal channel scheme can guarantee a maximum throughput of overall wireless network. (b) terminals can communicate and be located simultaneously in our system.
By taking advantage of positioning system, we can know the location of terminals, and such location information can be used to optimize network capacity through assigning appropriate channels. Assigning different channel to neighbouring APs is not only for optimizing network capacity, but also for improving the positioning accuracy due to that it can immigrate the interference among APs and receive accurate signal strength.
To confirm its effectiveness, we evaluate our approach by simulation. We compare our method with the single, random, and static methods and the LCCS method. T he results illustrate that the throughput of our channel assignment method is higher than other methods.

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In the region of Japan, broadband network and informatization have spread. However the field of agriculture has not come willingly. The infrastructure that has not been enough in mountainous areas, but various initiatives of computerization are being started using production and distribution as the subjects. Since this began in reality, there are still insufficient matters that have been resolved in regards to the technical validations and cost effectiveness. Therefore necessitates pouring in a tremendous amount of expertise, possibility is ICT and its related technologies of sensors. In our research and developments, we create demo hardware for the experiment using in the farm collected data. On the other hand, making study group with farmers for accumulation of data and experience. That visualized information configure to the platform of knowledge management. © 2012 Crown Copyright.

DOI： 10.1109/CISIS.2012.149

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Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, we propose a novel file-sharing system called Local Cloud Storage (LCS), based on the leading-edge device called "wireless memory" such as Eye-Fi and Flash Air. Most interesting point is that wireless configuration of multiple devices is previously configured to communicate with each other. As a result, these devices are recognized as just a memory on operating systems. If a user adds a file into the mounted memory, the file is distributed to other memory via the pre-configured wireless connection unconsciously. In addition to the concept of LCS, we also propose a novel Cross-layer Simultaneous Data Transmission Mechanism (CSDTM) based on UDP broadcast in 802.11 for accelerating single-hop data simultaneous distribution between devices. Of course, a normal TCP can be adopted for data transmission in LCS. However, by adopting UDP broadcast, we can realize simultaneous data transmission to multiple receivers. Since UDP broadcast in wireless network is so unreliable, it hasn't been used for data transmission. However, by adding our designed application layer retransmission mechanism, CSDTM achieves 100% data transmission in our assumed environment. Through the performance evaluation of CSDTM, we show that it transmit data to four receivers within half the time a conventional method takes. © 2012 IEEE.

DOI： 10.1109/CIT.2012.136

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As microblog services become increasingly popular, spatial-temporal text data has increased explosively. Many studies have proposed methods to spatially and temporally analyze an event, indicated by the text data. These studies have aimed a extracting the period and the location in which a specified topic frequently occurs. In this paper, we focus on a system that detects hot topic in a local area and during a particular period. There can be a variation in the words used even though the posts are essentially about the same hot topic. We propose a classification method that mitigates the variation of posted words related to the same topic. © 2012 Gesellschaft fuer Informatk.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Data caching is widely known as an effective power-saving technique, in which mobile devices use local caches instead of original data placed on a server, in order to reduce the power consumption necessary for network accesses. In such data caching, a cache invalidation mechanism is important in preventing these devices from unintentionally accessing invalid data. In this paper, we propose a broadcast-based protocol for cache invalidation in a location-aware system. The proposed protocol is designed to reduce the access time required for obtaining necessary invalidation reports through broadcast media and to avoid client-side sleep fragmentation while retrieving the reports. In the proposed protocol, a Bloom filter is used as the data structure of an invalidation report, in order to probabilistically check the invalidation of caches. Furthermore, we propose three broadcast scheduling methods that are intended to achieve flexible broadcasting structured by the Bloom filter: fragmentation avoidance scheduling method (FASM), metrics balancing scheduling method (MBSM), and minimizing access time scheduling method (MASM). The broadcast schedule is arranged for consecutive accesses to geographically neighboring invalidation reports. In addition, the effectiveness of the proposed methods is evaluated by simulation. The results indicate that the MBSM and MASM achieve a high rate of performance scheduling. Compared to the FASM, the MBSM reduces the access time by 34%, while the fragmentations on the resultant schedule increase by 40%, and the MASM reduces the access time by 40%, along with an 85% increase in the number of fragmentations.

DOI： 10.1587/transinfE94.D.1590

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A critical problem with wireless LAN-based positioning systems is the degradation in position estimation accuracy due to complex variation in the strength of the received signal, which originates in the nature of the underlying wireless channel. Handling such variation effectively is essential for the creation of practical wireless LAN-based positioning systems. In this paper, we propose a collaborative mechanism for correcting position estimation errors. The main objective is to assist users in correcting estimation errors manually by providing access to a shared body of accumulated information on corrections made by many other users. In particular, the mechanism is designed to enable any group of users to collaboratively build upon this body of information. Finally, we evaluate the effectiveness of the proposed mechanism through experiments. The results confirm that the proposed mechanism can provide effective estimation error correction in a realistic environment.

DOI： 10.1587/transcom.E94.B.649

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Language：English   Publishing type：Research paper (international conference proceedings)  

The objective of this paper is to clear out the relation ship between user's contexts and really used words in order to realize the context-aware Japanese text input method editor. We propose two spatial analyzing methods for finding location-dependent words among the huge Japanese data with geographical information. In this paper, we analyze a half million tweets gathered by our system since Dec. 2009. First, we analyze the standard deviation of latitude and longitude, which shows variation level. It is very simple way, but it can't find out the keywords that depend on several locations. For example, famous department stores distributed all over Japan have a large standard deviation, but they will depend on each location. Therefore, we propose three-tier breadth first search, where the searching area is divided into some square mesh, and we extract the area which include tweets more than average of upper area. In addition, we re-divide the extracted areas into more small areas. Our method can extract some locations for one keyword. © 2011 Springer-Verlag.

DOI： 10.1007/978-3-642-23866-6_27

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Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, we propose a context-aware Input Method Editor (IME) as a ubiquitous service for improving the input of text on mobile devices. In our proposed IME, it estimates the context of users according to position information from GPS (Global Positioning System) sensor or a presence information from the Internet. Simultaneously, it generates a personal context-aware dictionary dynamically from the keywords gotten via some APIs in the Internet. Currently, the information of user's context is also provided by NGN. In this paper, we explain the overview of our proposal and prototype implementation in Japanese. © 2010 IEEE.

DOI： 10.1109/ICNS.2010.8

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a method to evaluate effectiveness of our proposed context-aware text entry by using Twitter. We focus on "geo-tagged" public tweets because they include user's important contexts, real location and time. We also focus on TV program listing because 50% traffic of iPhone in Japan is generated from our home, in which I often tweets in watching a TV. Cyclical collecting system based on Streaming API and Search API of Twitter is proposed for gathering the target tweets efficiently. In order to find the relationship between user's contexts and really used words, we compare really-tweeted words with words obtained from Local Search API of Yahoo! Japan that is used for our context-aware text entry and words obtained from TV program listing. We analyze 471274 tweets that have been collected from 15 December 2009 to 10 June 2010 for specifying the relationship to landmark information and TV program. As a result, we show that 5.1% of tweets include landmark words, and 9% of tweets include TV program words. Additionally, we bring out that there are location dependent words and time dependent words.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In OLSR (Optimized Link State Routing Protocol), the multipoint relay mechanism has been introduced to minimize routing overhead for flooding control traffic. In order to achieve as low a routing overhead as possible, the selection of MPRs (multipoint relays) is designed to limit the overall number of such relays in the network. OLSR provides the shortest paths in terms of hops: however. it does not take into account the QoS (quality of service) requirements. Therefore, QOLSR (Quality OLSR), which adds a QoS extension to the OLSR, has been proposed. Although QOLSR provides the best QoS path, its selection process does not consider the number of MPRs, which causes an increase in the routing overhead. In this paper, we focus on the selection process of MPRs in link state QoS routing protocol. We propose three heuristics for high-efficiency selections: MIMS, MQES, and MCIS. The basic approach of these selections is to determine a smaller set of MPRs that provide better QoS paths between any two nodes. The main objective in doing so is to maximize the QoS effect while limiting the routing overhead. In addition, we evaluate the performance of the routing protocols with the proposed selections by simulation. The results indicate that MIMS and MCIS achieve high-efficiency selection; as compared to QOLSR, MIMS reduces the maintenance cost by 30%, while the throughput of the resultant path is decreased by 13%, and MCIS reduces the cost by 21% without any decrease in the throughput.

DOI： 10.1587/transfun.E92.A.2218

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Language：Japanese  

DOI： 10.15017/1517964

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Other Link： http://hdl.handle.net/2324/1517964

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper: we propose three heuristics for high efficiency selections of MPRs (multipoint relays) in link state QoS routing protocol: MIMS (maximizing integration metric selection), MQES (maximizing QoS-efficiency selection), and MCIS (minimizing cost-in efficiency selection). The basic approach of these selections is to determine a smaller set of MPRs that provide better QoS paths between any two nodes. The main objective in doing so is to maximize the QoS (quality of service) effect while limiting routing overhead for flooding control traffic. In addition, we evaluate the performance of the routing protocols with the proposed selections by simulation. The results indicate that the proposed methods achieve high-efficiency selection: as compared to an existing MPR selection taking into account the QoS requirements. MIMS reduces the maintenance cost by 30%, while the throughput of the resultant path is decreased by 13%. and MCIS reduces the cost by 21% without any decrease in the throughput.

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Language：English   Publisher：Faculty of Information Science and Electrical Engineering, Kyushu University  

DOI： 10.15017/1517960

CiNii Books

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Other Link： http://hdl.handle.net/2324/1517960

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The IEEE 802.11e standard defines several important techniques that guarantee the quality of service (QoS) of multimedia communications in wireless LAN applications. A key technique introduced in the standard is an efficient media access control based on the Hybrid Coordination Function (HCF), which assigns an appropriate transmission opportunity (TXOP) to each flow for satisfying several requirements on the flow, such as delay bound and communication bandwidth. Although the simple scheduler designed in HCF could provide an efficient tool to guarantee the QoS in wireless LAN applications, it has a serious drawback, wherein a useless bandwidth assignment frequently occurs. Such assignments occur primarily due to a limitation of the scheme, wherein all the flows share the same service interval (SI). In this paper, we propose a new scheduling scheme that associates each flow with its own SI according to the hardness of the required SI. The effect of this approach is experimentally evaluated by simulation, the results of which indicate that the number of admitted flows and network resource utilization increase due to the proposed scheme.

DOI： 10.1093/ietfec/e91-a.7.1562

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

P2P DHT (Peer-to-Peer Distributed Hash Table) is one of typical techniques for realizing an efficient management of shared resources distributed over a network and a keyword search over such networks in a fully distributed manner. In this paper, we propose a new method for supporting conjunctive queries in P2P DHT. The basic idea of the proposed technique is to share a global information on past trials by conducting a local caching of search results for conjunctive queries and by registering the fact to the global DHT. Such a result caching is expected to significantly reduce the amount of transmitted data compared with conventional schemes. The effect of the proposed method is experimentally evaluated by simulation. The result of experiments indicates that by using the proposed method, the amount of returned data is reduced by 60% compared with conventional P2P DHT which does not support conjunctive queries.

DOI： 10.1093/ietisy/e91-d.4.1023

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

In this paper, we consider power-saving techniques for mobile terminals in ubiquitous environment. As a means for realizing power-saving, we focus on caching techniques and attempt to save the power consumption required for wireless network devices by reducing meaningless transmissions using local caches. The use of caching techniques is required to manage the consistency between original data and their caches. Many existing protocols for keeping the cache consistency have been extensively developed during the past decade so far, and we investigate and summarize these existing techniques in this paper. Finally, we describe our target ubiquitous environment and propose a probabilistic cache consistency protocol.

DOI： 10.11485/itetr.32.30.0_81

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

This paper describes an efficient mechanism for correcting estimation errors inherent in existing WLAN-based localization systems. One of major problems in such localization systems is to degrade the estimation accuracy due to lacks of sufficient training data and temporal changes in received signal strength indications. We propose a location correction technique based on geographical locality of the estimation errors. This proposed correction technique is designed for exploiting users collaboration to improve the efficiency of the correction. More specifically, each surveyed location is associated with knowledge of error corrections that have been conducted by users, and is stored into a database. The system improves the usability of users' correction by presenting the knowledge corresponding to the estimated location.

DOI： 10.11485/itetr.32.30.0_87

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ACTA PRESS ANAHEIM  

In this paper, we propose a P2P information monitoring system to support the processing of conjunctive queries. The proposed system is an extension of PeerCQ, and our main contribution in this paper is the following three points: 1) we provide a detailed specification of Conjunctive Continual Queries (CCQs) that is an agent to check the satisfaction of a given conjunction, 2) we propose a mapping of CCQs to peers by considering the similarity of the referred data items, and 3) we improve the utility function used in PeerCQ in such a way that the trade-off between the load of each peer and the overall load of the system can be explicitly controlled. The effect of the proposed method is evaluated by simulation. The result of simulation indicates that the proposed utility functions certainly improves the performance of the resultant scheme, and the trade-off can be controlled by tuning a parameter in the utility function.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG BERLIN  

In this paper, we propose an efficient and practical routing scheme for MANETs based on a new routing metric called the free-degree of nodes. In the proposed routing scheme named FDAR (Free-Degree Adaptive Routing), it is intended to deliver data packets circumventing congested routes, so as to realize a short end-to-end delay and a moderate load balancing of the overall network. In addition, it tries to avoid frequent and unnecessary invocation of route discovery process which would significantly degrade the routing performance of the MANET. The effectiveness of the proposed scheme is evaluated by simulation. The result of simulations indicates that it certainly outperforms previous load-balanced routing, schemes including DLAR and LBAR, in terms of the packet loss rate and the average end-to-end delay.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ACTA PRESS ANAHEIM  

In this paper, we study the effect of shortcut links in overlay networks for distributed systems. In particular, we examine the effect of shortcuts in Content Addressable Network (CAN) which is known as a typical pure P2P network based on the notion of Distributed Hash Table (DHT). The proposed scheme is an extension of Kleinberg's method which was originally proposed for the study of small-world networks. The result of simulations indicates that the proposed shortcutting scheme significantly reduces the average number of hopcounts in a greedy routing, and the rate of improvement increases as increasing the number of nodes.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, we propose a new method to enhance the fault-tolerance of the Content Addressable Network (CAN), which is known as a typical pure P2P system based on the notion of Distributed Hash Table (DHT). The basic idea of the proposed method is to introduce redundancy to the management of index information distributed over the nodes in the given P2P network, by allowing each index to be assigned to several nodes, which was restricted to be one in the original CAN system. To keep the consistency among several copies of indices, we propose an efficient synchronization scheme based on the notion of labels assigned to each copy in a distinct manner. The performance of the proposed scheme is evaluated by simulation. The result of simulations indicates that the proposed scheme significantly enhances the fault-tolerance of the CAN system.

DOI： 10.1093/ietisy/e89-d.6.1923

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes a new class of parallel branch-and-bound (B&B) schemes. The main idea of the scheme is to focus on the functional parallelism instead of conventional data parallelism, and to support such a heterogeneous and irregular parallelism by using a collection of autonomous agents distributed over the network. After examining several implementation issues, we describe a detail of the prototype system implemented over eight PC's connected by a network. The result of experiments conducted over the prototype system indicates that the proposed parallel processing scheme significantly improves the performance of the underlying B&B scheme by adaptively switching exploring policies adopted by each agent participating to the problem solving.

DOI： 10.1093/ietisy/e89-d.6.1940

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, we propose a new localization scheme for wireless sensor networks consisting of a huge number of sensor nodes equipped with simple wireless communication devices such as wireless LAN and Bluetooth. The proposed scheme is based on the Point-In-Triangle (PIT) test proposed by He et al. The scheme is actually implemented by using Bluetooth devices of Class 2 standard, and the performance of the scheme is evaluated in an actual environment. The result of experiments indicates that the proposed scheme could realize a localization with an error of less than 2 m.

DOI： 10.1093/ietisy/e89-d.5.1614

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Content-Addressable Network (CAN) provides a mechanism that could retrieve objects in a P2P network by maintaining indices to those objects in a fully decentralized manner. In the CAN system, index caching is a useful technique for reducing the response time of retrieving objects. The key points of effective caching techniques are to improve cache hit ratio by actively sharing caches distributed over the P2P network with every node and to reduce a maintenance and/or routing overhead for locating the cache of a requested index. In this paper, we propose a new caching technique based on the notion of proxy-type caching techniques which have been widely used in WWW systems. It can achieve active cache sharing by incorporating the concept of proxy caching into the index access mechanism and locate a closer proxy cache of a requested index with a little routing overhead. By the result of simulations, we conclude that it can improve the response time of retrieving indices by 30% compared with conventional caching techniques.

DOI： 10.1093/ietisy/e89-d.2.555

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ACTA PRESS ANAHEIM  

P2P DHT (Peer-to-Peer Distributed Hash Table) is a typical technique to realize an efficient keyword search in pure P2P systems. In this paper, we propose a new method to support conjunctive queries in P2P DHT. The basic idea of the proposed method is to cache the result of conjunctive queries to each peer, and to register the fact to the DHT. In addition, in order to reduce the number of meaningless queries to DHT, it registers cached conjunctions to Bloom filter, and circulates it among all peers. The effect of the proposed method is experimentally evaluated by simulation. The result of experiments indicates that by using the proposed method, the amount of returned data reduces to 40%, and the number of queries reduces to 66%, compared with conventional P2P DHT.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

In wireless, LAN, several terminals could share a single communication channel by using an appropriate media access control (MAC) mechanism. However existing MAC schemes for wireless LAN have serious drawbacks such that it significantly degrades the throughput if it frequently occurs a collision of frames or a useless assignment of communication bandwidth. In this paper we propose a new MAC scheme for wireless LAN to realize an efficient utilization of the communication bandwidth while suppressing the probability of frame collisions. The basic idea of the scheme is to conduct a channel assignment for each group which is dynamically constructed based on the unique identifier that is assigned to each terminal beforehand. The scheme could be customized by appropriately tuning parameters according to the given communication environment. The effect of the scheme is estimated by simulation. By the result of simulations, it is confirmed that the proposed scheme could achieve a stable performance for any access frequency.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

IEEE802.11e standard adopts several important techniques to guarantee the quality of service (QoS) of multimedia communications in wireless LAN. A key technique introduced in the standard is an efficient media access control based on Hybrid Coordination Function (HCF), in which each flow is assigned an appropriate transmission opportunity (TXOP) to satisfy several requirements on the flow such as the delay bound and the communication bandwidth. Although it could provide an efficient tool to guarantee the QoS in wireless LAN, HCF has a serious drawback such that a useless bandwidth assignment frequently occurs, which is primarily due to the limitation of the scheme such that all flows share the same service interval (SI). In this paper, we propose a new scheduling scheme that associates each flow with its own SI according to the hardness of the delay bound The effect of the scheme is experimentally evaluated by simulation. The result of simulations indicates that the number of admitted flows and the data transmission rate certainly increase by the proposed scheme.

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Language：English   Publisher：Information Processing Society of Japan  

In this paper, we propose several distributed zone partitioning schemes for Content-Addressable Networks (CAN), that is known as a pure peer-to-peer system based on the Distributed Hash Table (DHT). The main objective of the proposed schemes is to balance the load of nodes in the CAN system, in such a way that every node receives almost the same number of inquiries from the other nodes in the system. The result of simulations implies that, by using the proposed schemes instead of a randomized zone partitioning scheme originally implemented in the CAN system, we could reduce the response time for each inquiry to less than 75%.

DOI： 10.2197/ipsjdc.1.54

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

In this paper, we propose a new method to enhance the fault-tolerance of the Content Addressable Network (CAN), which is known as a typical pure P2P system based on the notion of Distributed Hash Table (DHT). The basic idea of the proposed method is to introduce a redundancy to the management of index information distributed over the nodes in the network, by allowing each index to be assigned to several nodes, which was restricted to be one in the original CAN system. To keep the consistency among several copies of indices, we propose an efficient synchronization scheme based on the notion of labels assigned to each copy in a distinct manner. The performance of the proposed scheme is evaluated by simulation. The result of simulations indicates that the proposed scheme really enhances the fault-tolerance of the CAN system.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

In this paper we propose a new localization scheme for wireless sensor networks consisting of a huge number of sensor nodes equipped with simple wireless communication devices. The proposed scheme is based on the Point-In-Triangle (PIT) test proposed by He et al. The scheme is actually implemented by using Bluetooth devices of Class 2 standard, and the performance of the scheme is evaluated in an actual environment. The result of experiments indicates that the proposed scheme could realize a localization with an error of less than 2 m.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

In this paper, we propose a new routing protocol for mobile ad-hoc networks (MANET), which have attracted considerable attentions in recent years as a tool to realize flexible and robust communication environments in many critical application fields. The proposed protocol, called LQ-routing, is a proactive routing protocol based on the Q-routing protocol which was originally proposed for conventional wired networks. In order to reflect the mobility of hosts to the routing decision, which would cause frequent connection and disconnection of communication links between nearby hosts, we introduce the notion of lifetime to represent the stability of routes connecting to the destination. The performance of the proposed routing scheme is experimentally evaluated by using NS-2. The result of simulation indicates that by introducing the notion of lifetime to a simple combination of previous proactive routing scheme DSDV and the Q-routing, we could improve the performance of DSDV in terms of the packet loss rate and the average packet delay.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：C S R E A PRESS  

In this paper, we propose a caching technique for Content-Addressable Network (CAN). CAN provides a mechanism that could retrieve objects distributed over a P2P network by maintaining indices to those objects in a fully decentralized manner We introduce index caching to the CAN architecture for fast index retrieval and propose an efficient caching technique. The key point of the proposed technique is to achieve high cache hit ratio by exploiting access locality among participating hosts based on the notion of proxy caching techniques. By the result of simulations, we conclude that it can improve the response time of index retrieval by 30% compared with conventional techniques.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ACTA PRESS  

This paper proposes a new scheme to maintain a set of communication routes in a given interconnection network, that could be used as a basic component in localized QoS routing protocols. The proposed scheme is based on the notions of working set and randomization, that are general techniques used in several dynamic load balancing schemes in distributed systems. The result of simulations indicates that the proposed method is really effective to increase the success probability of path reservations without increasing the run-time overhead of conventional schemes.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we consider the admission control of communication flows under an environment with frequent retransmissions of packets. The basic idea of the proposed scheme is to improve Jamin et al.'s predictive service so as to take into account the effect of retransmissions of packets in a parameterized manner. The goodness of the scheme is evaluated by simulation. The result of simulations indicates that the proposed scheme can guarantee a predetermined delay bound without degrading the link utilization rate by appropriately selecting the value of a configurable parameter.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

In this paper, we propose several distributed zone partitioning schemes for Content-Addressable Networks (CAN), that is known as a pure peer-to-peer system based on the Distributed Hash Table (DHT). The main objective of the proposed schemes is to balance the load of nodes in the CAN system, in such a way that every node receives almost the same number of inquiries from the other nodes in the system. The result of simulations implies that, by using the proposed schemes instead of a randomized scheme originally implemented in the CAN system, we could reduce the response time for each inquiry to less than 75%.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

In this paper, we propose a scheme to dynamically establish shortcut links in Content Addressable Networks (CAN), based on a probabilistic method suggested by Kleinberg in 2000. The proposed scheme consists of the following three steps: 1) estimation of the total number of nodes participating to the P2P system, 2) dynamic adjustment of the probability distribution for selecting the target point of shortcut based on the estimated number, and 3) the establishment of shortcut to the nodes corresponding to the selected points. The performance of the resulting scheme is evaluated by simulation. The result of simulations implies that the shortcut significantly reduces the average number of hop counts, and the rate of improvement increases as increasing the number of nodes; e.g., the proposed method improves the hop counts in conventional CAN by 49% when it contains 4096 nodes. In addition, dynamic adjustment of the probability distribution improves the performance of the overall scheme, although the amount of improvement is less than "one hop" for relatively small netwotks examined in the simulation.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

In this paper, we propose a distributed algorithm for solving a resource location problem in distributed systems. The proposed algorithm is fully distributed in the sense that it assumes no centralized control, and has a remarkable property such that it can always find a target node satisfying a certain property, if any. The result of simulations implies that: (1) the performance of the underlying load sharing scheme can be significantly improved by increasing the preciseness of a node location, and (2) in the proposed scheme, the average number of inquiries per location is bounded by a very small value (e.g., only two inquiries are enough even when the underlying system consists of 100 nodes).

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

In this paper, we propose a fast branch-and-bound (B&B) algorithm for solving the multiprocessor scheduling problem with non-negligible communication time. The basic idea of our proposed method is to focus on an "inevitable" communication delay that could not be avoided in any assignment of tasks onto the processors. The proposed method is implemented as a part of B&B scheme, and the performance of the scheme is evaluated experimentally. The result of experiments implies that for randomly generated instances consisting of at most 300 tasks: 1) we could solve more than 90% of those instances within one minute if any communication takes zero time unit, 2) the percentage of hard instances increases by increasing the number of processors and the time required for each communication, and 3) the proposed method could achieve a significant improvement in increasing the lower bound of partial solutions especially for those hard instances. Those results suggest that the proposed method could output an optimum solution for many instances within a short computing time by combining it with a good heuristic to give a better upper bound.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

This paper proposes a new method to derive a refined lower bound on the makespan in the multiprocessor scheduling problem. The result of experiments implies that the proposed method really improves the performance of the underlying branch-and-bound scheme when it is applied at the root in the search tree; e.g., we could achieve a speedup of at least 7000 times in the best case.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, we propose a new job scheduling method for distributed parallel systems that can simultaneously achieve two main goals of the job scheduling in those systems: to minimize the execution time of a parallel job without disturbing the execution of the other jobs. We try to achieve those goals by introducing a new scheduler, called active scheduler, that dynamically controls the priority of parallel programs and balances the workload of host computers depending on the status of the underlying runtime environment. We implemented a prototype system of the scheduler to evaluate its effectiveness. The result of experiments implies that the overhead of introducing the active scheduler is at most 15% of the original execution time, and it is in fact effective to adjust the execution of parallel programs to an actual distributed environment in which many users execute their jobs simultaneously.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

This paper proposes a fast branch-and-bound algorithm for solving the multiprocessor scheduling problem. The key point of our method is the proposal of an efficient quadratic algorithm for calculating the Fernandez and Bussell's lower bound. In the following, we discuss about the trade-off between the cost for calculating a lower bound and the size of pruned subtrees. Several experiments am conducted to evaluate the goodness of the proposed method.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

In this paper, we propose a fast barrier synchronization protocol for broadcast networks. A key point of the protocol is to reduce the performance degradation by introducing a dynamic control of shared bus accesses. The proposed method is implemented on actual LAN and is compared with several protocols implemented in GAMMA system.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Verlag  

Mobile hosts can acquire location-dependent information at any place and be connected to a network from anywhere with wireless communication devices such as cellular phones, wireless LAN, etc. In such an environment we aim to construct a system software on which mobile hosts can share the location-dependent information with other hosts. It is, however, difficult for users who request location-dependent information to identify mobile hosts providing the information, since the system presents no mechanism to specify hosts by geographic location. In this paper we propose a location management system that manages locations of mobile hosts and enables users to specify location-dependent informations by their geographic locations. Since the location management system is employed for mobile computing, the system has the mechanism to reduce the overhead of location management on wireless communication. Moreover, we implement a part of this system and show that this system is suitable for mobile environment through the experiment.

DOI： 10.1007/3-540-45801-8_16

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Language：English   Publisher：電子情報通信学会  

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Language：Japanese  

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We are developing a simple collision avoidance system aiming at coexistence of wireless LAN (WLAN) and ZigBee which use a same frequency band. To realize the inter-standard collision avoidance system, it is important to use off-the-shelf wireless modules. We thus require a collision avoidance scheme that requires no modification on OS and hardware. In view of this, we present an AP-Assisted CTS-Blocking (AA CTS-Blocking) system. The AA CTS-Blocking enables us to prevent WLAN communications by applying the RTS/CTS method, which reduces collision between WLAN frames and ZigBee frames. The RTS/CTS scheme is normal process defined in a WLAN standard and requires no modification on OS or hardware. We implemented a data collection system utilizing our AA CTS-Blocking scheme and evaluated a ZigBee frame reception ratio under the WLAN interference.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The goal of our research is to realize super augmented reality (Super AR) in which reality can be augmented by powerful animal sensory perception. For example, as it is well known that dogs have an extraordinary olfactory sense, such dog's sense could be used to enhance human perception by integration of the sensory perception into the real world through Super AR technology. To achieve the objective, we are developing several techniques which acquire animal perception from brain waves of the animal and supplementary overlap the acquired perception on the real world. In this paper, we focus on a dog's olfactory sense as one of animal sensory perception and report an overview of our system and its technical subjects. Moreover, we also introduce an application, called EEGMap, which can record and display brain waves associated with location information where they have been recorded.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In our previous research, we have proposed an autonomous distributed localization system to realize on-demand location-based services. This distributed localization system provides a location-based service as a Web service and distributes network traffic all over the AWPN based on distribution of user devices. Inherently, the distributed localization system faces a problem of network congestion when user devices are gathering in one place. In this paper, we propose a probabilistic association scheme to overcome this problem. WiFi APs returns failure association response with a certain probability that depends on the number of associated devices, which promotes device assocation to other APs. We perform simulations and show that our probabilistic association scheme effectively distributes device associations.

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Multipoint relaying is a key concept adopted in the optimized link state routing protocol (OLSR). It realizes efficient flooding of topology control (TC) messages. It simultaneously supports generating small topology information which is enough to find the shortest path for any pair of nodes. In this paper, we propose a method to find more efficient multipoint relay (MPR) set, in terms of reducing topology control traffic of OLSR. Our method shares MPRs between a node and its neighbor nodes, to reduce the MPR ratio. The MPR ratio is defined as the number of MPR nodes divided by the total number of nodes in the network. By decreasing the MPR ratio, the number of TC message generation is decreased. To overlap the MPR set with MPR sets of the neighbors, each node computes the degree of coverage for each of its MPRs, and appends the degrees into HELLO messages. When a node computes its MPR set, the node intends to share MPRs by referring neighbors&#039; MPR sets and the degrees of their MPRs. Our MPR selection algorithm keeps the size of MPR set no more than that of the conventional MPR selection. Through simulations, the MPR ratio and the number of OLSR packets reduce by 6% and 4%, respectively, in moderately dense networks. © 2013 IEEE.

DOI： 10.1109/WoWMoM.2013.6583478

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Such as minimization, cost reduction, and higher functionalization of sensors, the evolving wireless sensor network technologies are influencing more strongly especially to precision agriculture. In precision agriculture, environmental sensing is very important element. Now, in order to construct environmental sensing in a tea garden, we considered to introduce a sensor network. However, because it becomes an agricultural sparse wireless sensor network(ASWSN), it causes the problem that some sensor node cannot transmit with another node by ad-hoc transmission because of their farther distance. Additionally, it also causes necessity to ensure the enough power supply. In this paper, we develop the low-cost sensor node prototype using Arduino. It realizes power supply from solar and wind, and realized low-power Data MULE using either an ultrasonic distance sensor or a 315 MHz transceiver on sensor node's wakeup. Finally, we evaluate about the driving time by simulation, and report the result on installing in real-world outdoor experiment.

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In this paper, we propose the method to virtualize smartphone sensors on Android so that other devices can use it over Bluetooth. We also propose traffic control method according to the amount of change in the measured data in order to reduce power consumption when using another device's sensor. We prototype the application using virtualized accelerometer. And we report the results of evaluating the power consumption of the device and the accuracy of the sensor value.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, a user often carries several smartphones and/or tablets with multiple overlapped sensor functions. In addition, short operating time in such portable devices becomes a serious problem, as compared with the previous generations. Thus, we propose a method to extend total operating time by distributing and sharing such overlapped functions between multiple portable devices. For example, one portable device operates with a GPS device which consumes large power and sends the acquired position to another device through a Bluetooth communication. The proposed method makes it possible to balance the power consumption between the portable devices. In this paper, we measure the power required for operating sensor functions and for communications between terminals. Moreover, we consider the decision algorithm for sharing and distributing functions between portable devices based on the results.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we propose the method to virtualize smartphone sensors on Android so that other devices can use it over Bluetooth. We also propose traffic control method according to the amount of change in the measured data in order to reduce power consumption when using another device's sensor. We prototype the application using virtualized accelerometer. And we report the results of evaluating the power consumption of the device and the accuracy of the sensor value.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Recently, a user often carries several smartphones and/or tablets with multiple overlapped sensor functions. In addition, short operating time in such portable devices becomes a serious problem, as compared with the previous generations. Thus, we propose a method to extend total operating time by distributing and sharing such overlapped functions between multiple portable devices. For example, one portable device operates with a GPS device which consumes large power and sends the acquired position to another device through a Bluetooth communication. The proposed method makes it possible to balance the power consumption between the portable devices. In this paper, we measure the power required for operating sensor functions and for communications between terminals. Moreover, we consider the decision algorithm for sharing and distributing functions between portable devices based on the results.

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We have developed an adhoc wireless positioning network (AWPN) that can temporarily and easily provide a positioning area, even in indoor environments. An AWPN provides a network-side positioning capability on a wireless mesh network, i.e., the network is constructed by deploying wireless LAN access points (APs) in the positioning area. However, the positioning performance is not enough due to the fact that an AWPN is mainly intended to make its deployment and configuration easier. In this paper, we propose a multilateration-based lo-calization scheme which can improve the positioning accuracy in network-side localization with terminal-originated RSSI variations. Moreover, we evaluate the effectiveness of the proposed scheme in an actual environment. As a result, the proposed scheme improves the accuracy for estimating the position of a fixed terminal over 13.4% as compared with an existing method, and reduces terminal-originated RSSI variations .In addition, we confirm that it can stably estimate the trajectory of a moving terminal.

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For actual scenes of information-oriented construction, it is required to develop easy and adhoc localization technology in indoor environments, since one of the goals is to realize location management of construction workers, e.g., it is used to avoid entering dangerous areas and taking dangerous behaviors. For that purpose, we aim to create an IT-colorcone with wireless communication capability and realize the adhoc positioning environment by deploying multiple IT-colorcones to a positioning area. In this paper, we propose an accurate localization method that provide an appropriate modeling of radio wave propagation of each IT-colorcone through an analysis of the characteristic of RSSIs from other IT-colorcones. Moreover, we evaluate the effectiveness of the proposed method. From the result, we confirm that the average error was improved by 30%.

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In this paper, we focus on monitoring environments with wireless sensor networks wherein mobile sink nodes exist to traverse a sensing field in a spatial-temporal specific manner and aggregate some types of environment data with different deadline constraints. For such environments, we propose an energy-efficient data aggregation method which reduces intermediate transmissions in multi-hop communications while guaranteeing the deadlines. The basic approach of the proposed method is to temporarily gather (or buffer) the observed data into several sensor nodes existing around the moving path of the mobile sink that would meet their deadline at the next visit and then, to transfer the buffered data to the mobile sink node when it visits the sensor nodes. In addition, we also propose a mobilesink-initiated proactive routing protocol (MIPR-LC) which efficiently constructs routes to buffering nodes on each sensor node. Moreover, we evaluate the proposed aggregation method and routing protocol by simulation to show their effectiveness. As a result, we confirm that the MIPR-LC method can reduce less than 23 % in energy consumption as compared with a simple routing protocol and also the mobile sink nodes can gather almost all the observation data within the deadline.

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It is required to realize wireless network selections which automatically select an appropriate network from all available ones according to user's context information. The goal of our project is to extract common functions in a variety of wireless network selections for use in the development and to provide these functions as a software framework. By using the proposed software framework, it is easy to develop wireless network selections according to individual user's situations. In this technology exhibit, we present an application for wireless network selections using the proposed software framework.

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It is required to realize wireless network selections which automatically select an appropriate network from all available ones according to user's context information. The goal of our project is to extract common functions in a variety of wireless network selections for use in the development and to provide these functions as a software framework. By using the proposed software framework, it is easy to develop wireless network selections according to individual user's situations. In this technology exhibit, we present an application for wireless network selections using the proposed software framework.

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Multipoint relays (MPRs) support efficient flooding of topology control messages in OLSR. Since the shortest path is constructed as a sequence of MPRs, MPRs are the nodes of the backbone network. In this paper, we explore dense wireless multi-hop networks, and analyze the density of MPRs in such networks. We explain three properties to increase the number of MPRs: (1) each MPR is far from its selector, (2) MPRs of a node are close to each other, and (3) even if two nodes are close to each other, they tend to select different MPRs, in dense networks. These properties make the density of MPRs high. Concerning the third property, we explain a non-distributed MPR selection algorithm, to show the chance to select the same MPRs with neighbors. Finally, we measure the MPR ratio and the routing overhead of topology control messages, in dense wireless multi-hop networks by simulation. © 2011 IEEE.

DOI： 10.1109/ICNC.2011.27

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In this study, we propose a deadline-aware aggregation method for energy-efficient wireless sensor networks. Data aggregation method using a mobile sink, while increasing the delay the data is collected, there is a feature that can reduce power consumption in applications where the delay is acceptable is a method useful. However, its performance is highly dependent on behavior of a mobile sink, there is a problem that can not meet the application request power and delay. The simulation revealed the problem. And, as a way to solve this problem, we propose to switch the aggregation method according to the allowable delay time. The proposed scheme is expected that a sensor predict the time to contact a mobile sink and change the aggregation method using a mobile sink and the aggregation method for multi-hop network by comparing the allowable delay time.

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In this paper, we present a serious degradation problem with positioning accuracy that occurs when applying wireless LAN-based positioning systems to a tunnel construction site and propose a correction method to solve the problem. The degradation is due to considerable time variation in the received signal strength. In order to mitigate the impact of the time variation, the proposed method corrects the measured signal strength. It is designed for two localization methods: i.e., location fingerprinting and multi-lateration. Furthermore, we evaluate the effectiveness of the proposed method by experiments at an actual tunnel construction site. From the results, we confirm that location fingerprinting with the proposed correction can improve the successful ratio by 5.4% and the average error by 28%, as compared to that without the correction. Moreover, as for multi-lateration with the correction, the average error is reduced by 37%.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

The development of wireless LAN-based positioning technologies has been proceeding to realize indoor location-depended services that require high positioning accuracy. In this paper, we propose an interpolation method of training data for location fingerprinting to reduce the cost required for building the training data. More specifically, a critical problem with location fingerprinting is considerable cost for measuring received signal strengths at every location where the positioning is possible. In the proposed method, a part of the training data is interpolated from data actually observed at several locations using a path loss model considering wall attenuation. Furthermore, to confirm the effectiveness of the proposed method, we examine the performance of location estimation and verify the interpolated data. As compared with a conventional method, the proposed method can improve the positioning accuracy by 15%.

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An explosive spread of handheld devices with wireless communication capability, such as cellular phone and PDA, rapidly increases opportunity for data communication through temporarily constructed short-range wireless network. An easy realization of secure communication in such network is indispensable to user-friendly networking environment towards popularization of short-range wireless networks. Resently a common key sharing technique which generates the encryption key on a communication pair rather than distributes a prepared key from one to the other are proposed. The main idea of the proposed technique is to generate a common key based on the variation of multipath fading channel caused by shaking the sender device. In this paper, we implement a prototype system realizing the proposed method and evaluate the robustness of the proposed method.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The development of wireless LAN-based positioning technologies has been proceeding to realize indoor location-depended services that require high positioning accuracy. In this paper, we propose an interpolation method of training data for location fingerprinting to reduce the cost required for building the training data. More specifically, a critical problem with location fingerprinting is considerable cost for measuring received signal strengths at every location where the positioning is possible. In the proposed method, a part of the training data is interpolated from data actually observed at several locations using a path loss model considering wall attenuation. Furthermore, to confirm the effectiveness of the proposed method, we examine the performance of location estimation and verify the interpolated data. As compared with a conventional method, the proposed method can improve the positioning accuracy by 15%.

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With the spread of mobile phones, society has become sensitive about the use of manners. For example, we have been encouraged to turn off our cell phone while riding the train. In addition, you should make silent mode during a movie theater and a meeting. On the other hand, we want to prevent it from missing the notice from a cell-phone while we are in the house or we walk or we put a cell-phone in a bag. Therefore, the technique for switching the setting of the terminal automatically and appropriately is requested. In this study, we propose a method for automatic mode change by performing the coordination around the terminal. In our system, the mode is judged by recognizing surrounding terminals using the location of the terminal, and sharing mode information between those, and calculating the ratio of the manner mode. In this paper, we designed our system and created a simple prototype of the proposed system, conducted experiments and discussion.

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Other Link： http://id.nii.ac.jp/1001/00072942/

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Other Link： http://id.nii.ac.jp/1001/00072953/

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In this paper, we propose a local cloud storage which is extemporarily constructed through short-range wireless devices. The proposed storage enables neighbor users to share their own files without the steps of network configuration and setup, and the aid of any backbone network, i.e., the file sharing is realized by only mounting our designed small devices onto users' nodes. We have designed a file sharing protocol for such short-range wireless communication and realized its prototype system.

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A spread of short-range and infrastructure-less wireless communication devices increases opportunities for temporarily exchanging information in a face-to-face style, called wireless face-to-face communication. In such wireless communication, a critical issue with secure information exchange is encryption key sharing without the aid of any centralized administration. In this paper, we propose a novel key sharing technique for wireless face-to-face communications. The main idea is to generate the same encryption key on a communication pair using received signal strength indicators (RSSI) from observable wireless LAN appliances, rather than distribute a prepared key between the pair. The generation for the same key is realized by utilizing the similarity of RSSI observed within a small area. Furthermore, we examine the successful ratio for generating the same key and consider the security level for the proposed method.

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Laptop computers and cellular phones often have the capability for short-range wireless communication such as adhoc mode in wireless LAN and Bluetooth. However, the use of the capability is limited due to the lack of consideration for short- range communications in conventional communication protocols; i.e., an unnatural and troublesome procedure is required to specify targets especially within a nearby area. In this paper, we propose a symbolic device to support short-range wireless communications that provides the ability to specify a target on the real-world environment. More specifically, a short-range communication device is logically concerned with its corresponding symbolic device and the short-range communication with a target is established by linking the symbol device with the target directly or indirectly. Furthermore, we designed and implemented a prototype system for the proposed device using wired and wireless LAN.

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Other Link： http://id.nii.ac.jp/1001/00070242/

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In this paper, we propose an authentication technique which is based on the generation technique of common information exploiting characteristics of multipath fading channel for handheld devices. The main idea of the proposed technique is to extract the underlying wireless channel characteristics from the multipath fading of broadcast communication, and authenticate the communication pair whether the information extracted on the sender is the same as that on the receiver or not; the agreement would be achieved between only a regular communication pair by using the generation technique of common information. Moreover, the proposed method can prevent spoofing attack and man-in-the-middle attack by employing a broadcast-based authentication protocol. Finally, we evaluate the effectiveness of the proposed method by checking a safety against various attacks.

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In this paper, we propose a novel channel assignment for positioning system in wireless mesh networks. In wireless mesh networks, for avoiding radio wave interference from other access points, different access points, that are within transmission range of each other, are required to operate on different channels. On the other hand, as for realizing highly accurate position estimation, the different access points need to use a single channel, since as many access points as possible can measure wireless transmissions on the same channel from a mobile device. We aim to achieve a network system that can realize both broadband communication and accurate localization in wireless mesh networks. The proposed method strikes a balance between the two conflicting objectives on the channel assignment.

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Other Link： http://id.nii.ac.jp/1001/00069394/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

An explosive spread of handheld devices with wireless communication capability, such as smart phone and cellular phone, rapidly increases opportunity for data communication using ad-hoc short-range wireless network. An easy realization of secure communication in such network is indispensable to user-friendly networking environment towards next generation ubiquitous computing. In this paper, we propose an encryption key sharing technique which generates the same encryption key on a communication pair rather than distribute a prepared key from one to the other. The main idea of the proposed technique is to generate the key based on the variation of multipath fading channel caused by shaking a sender-receiver pair. Furthermore, we construct a prototype system realizing the proposed technique and evaluate the effectiveness of it in an actual environment.

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In this paper, we propose a reduction technique for traffic overhead occured in location estimation for wireless mesh networks. For realizing the localization, a server has to collect the data for received signal strength observed in all access points through the mesh network. The communication overhead for the collection can stress the network, which leads to the interference with data communication mainly intended by the network. The main idea of the proposed method is to decentralize the calculation required for the localization. The communication can be reduced by aggregating and relaying partial calculated results rather than raw observation data. Furthermore, we evaluate the effectiveness of the proposed method by simulation.

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Other Link： http://id.nii.ac.jp/1001/00069131/

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We have proposed a network-based context-aware Japanese input method editor to enhance user's comfortability at text inputting on mobile devices. In this paper, we describe the detail of our implementations, including the prototype with a location information, and the preliminary experiment for verifying a relationship between a location and an input sentence.

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We have proposed a network-based context-aware Japanese input method editor to enhance user's comfortability at text inputting on mobile devices. In this paper, we describe the detail of our implementations, including the prototype with a location information, and the preliminary experiment for verifying a relationship between a location and an input sentence.

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In this paper, we propose a context-aware IME (Input Method Editor) for improving the input of Japanese on mobile devices. In our proposed IME, it estimates the context of users according to a position information from GPS (Global Positioning System) sensor or a presence information from the Internet. Simultaneously, it generates a personal context-aware dictionary dynamically from the keywords gotten via some APIs in the Internet. Currently, the information of user's context is also provided by NGN. In this paper, we explain the overview of our proposal and our prototype implementation.

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In this paper, we propose name resolution middleware that involves positional awareness to identify target hosts in wireless visible area communication (WVAC). WVAC is a wireless communication network that enables users to exchange information with nearby hosts, especially within the users&#039; visible area, wherein the underlying network can be locally and temporarily constructed without the aid of any centralized administration. In such communication, the proposed middleware assists the user to intuitively identify a target host by presenting the relative positional relationship among the neighbor hosts. The middleware possesses the following characteristics: (1) it provides simple APIs to be easily utilized by various applications, (2) a dedicated server preliminarily located in the network is not required to operate it, and (3) it adopts a positioning method that could estimate the relative locations of neighbor hosts without any pre-configuration. Finally, we construct a prototype system and evaluate the middleware using this system. The results indicate that this middleware can sufficiently work even on resourcelimited mobile devices. © 2009 IEEE.

DOI： 10.1109/AINA.2009.55

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A spread of mobile terminal equipped with short-range wireless communication device has increased the demand for file sharing through local and temporary wireless network. However, due to the ease of sniffing in such network, the file sharing has a risk of leaking in the communication. In this paper, we focus on secure face-to-face information exchange especially in wireless visible area network (WVAC) which is locally and temporarily constructed to communicate with visible users. More concretely, we propose a mutual authentication method for WVAC. The proposed method enables a communication pair to mutually authenticate their public keys without any certificate authority. The main idea of the proposed method is to authenticate the public keys of the communication pair based on trusting relationship obtained by a face-to-face situation. Additionally, users obviously can comprehend authenticated public keys for others due to man-in-the-loop approach included in the process of the authentication.

DOI： 10.15017/1517964

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In this paper, we report experimental results for the impact of environmental dynamics to variations of received signal strength for network-based location estimation. In network-based location estimation, the position of a client can be determined by using signal strength of the client's frame transmissions sniffed at several access points. The client does not require dedicated equipments and software to realize the network-based location estimation. In this experiment, we examine the variations of received signal strength affected by differences among wireless LAN devices, radio interference, movements of people, and temporal environmental variations. Additionally, we consider an error correction technique in network-based location estimation to deal with the unpredictable variations.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The feature model can contain hundreds of features, that makes it impossible to be manually organized in an easy-to understand mannar. And a lot of tree-drawing algorithms have been proposed so far, but they can not be used to draw feature model directly. This is because these algorithms draw a tree based on general graph topologies, not on feature meanings. In this paper, we propose a drawing algorithm designed for feature model. The propose algorithm can draw the formatted hierarchical graph based on the relationship between features for a given feature model. We have implemented it and confirmed that the graph generated by the algorithm is clearly organized while keeping the feature meanings.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The feature model can contain hundreds of features, that makes it impossible to be manually organized in an easy-to understand mannar. And a lot of tree-drawing algorithms have been proposed so far, but they can not be used to draw feature model directly. This is because these algorithms draw a tree based on general graph topologies, not on feature meanings. In this paper, we propose a drawing algorithm designed for feature model. The propose algorithm can draw the formatted hierarchical graph based on the relationship between features for a given feature model. We have implemented it and confirmed that the graph generated by the algorithm is clearly organized while keeping the feature meanings.

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We propose a load-balancing technique which could balance the load for estimating relative locations using WiPS (Wireless LAN based indoor Positioning System) with nodes participating in the network. The main idea of the technique is to employ a decentralized algorithm for the relative location estimation. In this paper, we report the evaluation for the impact of adopting the algorithm on the estimation performance. The results of simulation indicates that the probability of the distance error of 10m or more is suppressed to about 3%.

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A spread of mobile terminal equipped with short-range wireless communication device has increased the demand for file sharing through local and temporary wireless network. However, due to the ease of sniffing in such network, the file sharing has a risk of leaking in the communication. In this paper, we focus on secure face-to-face information exchange especially in wireless visible area network (WVAN) which is locally and temporarily constructed to communicate with visible users. More concretely, we propose a mutual authentication method for WVAN. The proposed method enables a communication pair to mutually authenticate their public keys without any certificate authority. The main idea of the proposed method is to authenticate the public keys of the communication pair based on trusting relationship obtained by a face-to-face situation. Additionally, users obviously can comprehend authenticated public keys for others due to a man-in-the-loop approach included in the process of the authentication.

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In this paper, we propose a broadcast-based protocol for cache invalidation in location-aware system, wherein each client uses local caches of location dependent data to reduce network accesses. The proposed protocol is designed to avoid sleep fragmentation in clients and reduce waiting time for getting required invalidation information. To realize short waiting time, we use Bloom filter to express and compress invalidation information and shorten time for accesses to nearby invalidation information on broadcast schedule. Also we propose three broadcast scheduling methods: FASM (Fragmentation Avoidance Scheduling Method), MBSM (Metrics Balancing Scheduling Method), and MASM (Minimizing Access time Scheduling Method). The effectiveness of the proposed methods is evaluated by simulation.

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We have developed a middleware system to identify communication targets in wireless visible area communication. The system uses the WiPS method which calculates relative positional relationship among nearby hosts, but it has several problems; i.e., high computational load is required on the host that acts as a server, and relative locations for all hosts are estimated regardless of whether the hosts have moved or not. In this paper, we propose a load-balancing technique to overcome these problems. The proposed method distributes the server load among hosts by transferring the server ability to other hosts. Furthermore, it reduces the computation time and communication overhead by considering only moving hosts in estimating the relative locations. The effectiveness of the proposed method is evaluated by simulation.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

A critical problem with wireless LAN-based positioning systems is degradation in the estimation accuracy due to difference between employing wireless LAN devices. In this paper, we propose a device normalization technique that mitigates the degradation by analyzing and calibrating the difference in the location estimation. More specifically, we introduce calibration phase between the survey phase and estimation phase in the process of the scene analysis. The calibration phase distinguishes the difference automatically, and the estimation phase corrects observation data based on the extracted difference. Furthermore, the proposed technique reduces calibration cost for collecting calibration data. We evaluate the effectiveness of the proposed technique by experiments. The results indicate that it improves the estimation accuracy compared with no calibration.

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Other Link： http://id.nii.ac.jp/1001/00061191/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

A critical problem with wireless LAN-based positioning systems is degradation in the estimation accuracy due to variations in the strength of the received signal that originate in the nature of the underlying wireless channel. Coping with these complex variations is essential to realizing an accurate and reliable positioning system. Here we propose a collaborative mechanism for correcting positional estimation errors. The main objective is to assist users to manually correct for estimation errors by providing access to a shared body of accumulated information on corrections made by other users. In particular, the mechanism is designed to enable any group of users to collaboratively build upon this body of information. Finally, we evaluate the potential effectiveness of the proposed mechanism through experiments. The results demonstrate that the proposed mechanism can provide corrections for estimation errors in a realistic environment.

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Other Link： http://id.nii.ac.jp/1001/00061190/

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We have developed wireless visible area communication (WVAC) which is a wireless communication network that enables users to exchange information with nearby hosts, especially within the users' visible area, wherein the underlying network can be locally and temporarily constructed without the aid of any centralized administration. In this paper, we discuss software supporting identification of target hosts in WVAC, and propose name resolution middleware assisting the user to intuitively identify a target host. The main idea of the assistance is to present the relative positional relationship among the neighbor hosts. The middleware possesses the following characteristics: (1) it provides simple APIs to be easily utilized by various applications, (2) a dedicated server preliminarily located in the network is not required to operate it, and (3) it adopts a positioning method that could estimate the relative locations of neighbor hosts without any pre-configuration. Finally, we construct a prototype system and evaluate the middleware using this system. The results indicate that this middleware can sufficiently work even on resource-limited mobile devices.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Product line, or PL, is a development method eases software development for more kinds and less quantity software by requirement from the market. In PL development, commonarities and variabilities between each product are represented as features mean characteristics and functions. The development of products based on the feature model is realized by the management of development assets based on the feature model. We propose a method of modeling for PL by using feature model and Reusable Asset Specification, or RAS. This method uses links between a feature and an element in RAS, and makes these models as PL development asset. This paper shows an outline, a building method, and an examples of the model.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a routing protocol for solving gray zones problem in MANET. By selecting a node existing within gray zones as an intermediate node of a route, the throughput of the route is degraded due to high packet drop rate. In the proposed protocol, the selection of an intermediate node is based on a two-phase approach, to improve the throughput of the route as high as possible, while keeping the network connectivity. We implement the proposed protocol based on AODV and evaluate it in an actual environment. The results indicatesthat the throughput for the proposed protocol is about four times higher than that of existing protocols. And it can also keep the network connectivity even when high throughput routes cannot be constructed.

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Other Link： http://id.nii.ac.jp/1001/00045984/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In software product line development, some modules are modified depending on feature selection due to variabilitiy among product line members. To perform unit testing for such modules, feature selection must be taken account for as additional test inputs. The number of test cases can be reduced by extracting significant feature selection from possible feature selection. In this paper, we define the reletions between features and modules representing how the feature impacts on the module. Moreover, we introduce the method to get the combination of feature selection which must be considered on unit testing. Since, our method is well defined as a process except for the first step in which the relations are defined, it can be automated to reduce developers' burden.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a new OLSR-based routing protocol which enables reflecting link quality with lower routing overheads. Link quality metrics improve communication quality of link-state routing protocol, however this results in much more advertising messages. Our protocol copes with such conflicting goals by introducing an adaptive parameter. Simulation based evaluation shows our protocol can form high-quality routes with fewer advertising messages.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Many home electric appliances and sensors can be organically linked to each other through home networks due to the increasing communication capability of these devices. One of the important techniques in such a home network is context awareness in which pre-determined actions can be taken according to situations (context) on real world. We propose a distributed framework that can efficiently manage and provide contexts which are based on information obtained by sensors distributed over the network. Especially, the proposed framework can support for detecting transitions of a context in an event-driven manner. In this technology exhibit, we exhibit our sensor devices designed for home networks called UDSS (Ubiquitous Data Source Server) and explain the distributed framework for the sensor devices.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We develop a positioning system (WiPS) that can estimate the location of a wireless LAN terminal, based on the measurement of received signal strength indicators (RSSI) to other terminals. The WiPS has the following properties; it can work without pre-calibrations and on ordinary wireless devices, and can improve the positioning accuracy as increasing the density of neighboring terminals. In this technology exhibit, we give a demonstration of the positioning for multiple mobile terminals using the WiPS.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

Many home electric appliances and sensors can be organically linked to each other through a home network due to the increasing communication capability of these devices. In such a home network, one of the important techniques is context awareness in which predetermined actions can be taken according to situations on real world called context. In this paper, we propose a new framework which can help to detect transitions of context based on information obtained by sensors distributed over the home network. More concretely, it provides a sensor abstraction for handling sensors in a uniform fashion and an efficient mechanism that can detect complex events concerned with sensing data on multiple sensors.

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Other Link： http://id.nii.ac.jp/1001/00046252/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In software product line engineering, change of market requirements causes modification of reusable artifacts, namely core assets. It is essential to estimate core assets modification cost on planning the modification. Core assets include not only codes but also various artifacts such as software design documents. However, most of existing cost models estimate core assets modification cost based on LOC. Our method evaluates a modification cost for each type of core assets and estimates core assets modification cost by summing up, those costs in order to get more accurate estimation than existing methods. The method analyzes impact on classes, which is caused by modification of features. The modification cost for each type of core assets is evaluated based on the number of features, classes and LOC to be modified.

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Other Link： http://id.nii.ac.jp/1001/00046000/

Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

Active queue management (AQM) is a novel technique to realize a smooth congestion control in communication networks, which is expected to work effectively by combining it with end-to-end congestion control schemes such as the window control adopted in TCP. Although it has been proposed a lot of AQM schemes in the literature, an appropriate tuning of parameters used in those schemes is recognized as a challenging problem to be overcome. In this paper, we propose a new AQM scheme based on a load level prediction of bottleneck links, and on a combination of queue-based and rate-based AQM schemes in multiple time scales. Different from most of conventional AQM schemes, the proposed scheme, called Switch-RED (SwRED), employs a new packet drop strategy based on a macroscopic analysis of the queue dynamics. The performance of the resultant scheme is evaluated by simulation. The result of simulations indicates that SwRED realizes a more stable queue behavior compared with previous schemese, i.e., it realizes a low queuing delay and a low packet loss rate while keeping a high link utilization.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose an efficient and practical ad hoc routing protocol, based on the notion of free degree of node, namely, the Free Degree Adaptive Routing (FDAR) protocol. The proposed scheme is intended to route data packets circumventing congested paths so as to balance traffic load over the network and lower end-to-end delay. Additionally, we also establish a tolerance policy to avoid excessive overhead in order to improve the data delivery reliability and stability of network. Simulation results indicate that FDAR outperforms DSR in terms of average end-to-end delay and average end-to-end throughput.

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Other Link： http://id.nii.ac.jp/1001/00046022/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

P2P DHT (Peer-to-Peer Distributed Hash Table) is one of typical techniques for realizing an efficient management of shared resources distributed over a network, and a keyword search over such networks in a fully distributed manner. In this paper, we propose a new method for supporting conjunctive queries in P2P DHT. The proposed method is based on a sharing of global information on past trials by locally caching the search result for conjunctive queries. The idea of the method is to reduce the number of meaningless inquiries by registering cached conjunctions to the bloom filter, and by circulating it among all peers. The effect of the proposed method is experimentally evaluated by simulation. The result of experiments indicates that by using the proposed method, the number of inquiries is reduced by 66%, compared with a method which does not use the bloom filter.

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Other Link： http://id.nii.ac.jp/1001/00046023/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a P2P information monitoring system that supports the processing of conjunctive queries. The proposed system is an extension of PeerCQ, and our main contribution in this paper is the following three points: 1) we provide a detailed specification of Conjunctive Continual Queries (CCQs) that is an agent to check the satisfaction of a given conjunction, 2) we propose a mapping of CCQs to peers by considering the similarity of the referred data items, and 3) we improve the utility function used in PeerCQ in such a way that the trade-off between the load of each peer and the overall load of the system can be explicitly controlled. The effect of the proposed method is evaluated by simulation. The result of simulation indicates that the proposed utility functions certainly improves the performance of the resultant scheme, and the trade-off can be controlled by tuning a parameter used in the utility function.

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Other Link： http://id.nii.ac.jp/1001/00025470/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose an equalization scheme of address spaces for DART (Dynamic Address RouTing) that is a routing protocol designed for a large scale adhoc network. In DART, the improvement of the scalability is achieved by using two main techniques; i.e., a dynamic and hierarchical addressing and a simplified routing. However, autonomous address allocation in each node causes the imbalance of address spaces assigned to nodes, which leads to significant performance degradation. In order to solve the problem, the proposed method realizes a re-addressing technique for the imbalance of address spaces. The effect of the proposed method is evaluated by simulation. The result indicates that by the effect of equalization, the proposed method shortens the path length by about 10% compared with DART protocol and reduces the size of routing tables.

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Other Link： http://id.nii.ac.jp/1001/00025472/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a direction detection system using passive RFID that detects the direction of an RFID reader. The electromagnetic induction type RFID has a characteristic property such that the read range varies according to the angle between a tag and a reader. The basic idea of the detection mechanism is to use multiple tags and exploit such property in designing the placement of these tags. More concretely, the placement is designed for the reader to read different tags in each detectable direction. The system estimates the direction from tags that could be read by the reader. The proposed system was actually implemented by using passive RFID devices operating at 13.56MHz, and the performance of the system was evaluated in a realistic environment. The result of experiments indicates that the proposed system could distinguish eight directions within 9cm.

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Other Link： http://id.nii.ac.jp/1001/00041134/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we propose a direction detection system using passive RFID that detects the direction of an RFID reader. The electromagnetic induction type RFID has a characteristic property such that the read range varies according to the angle between a tag and a reader. The basic idea of the detection mechanism is to use multiple tags and exploit such property in designing the placement of these tags. More concretely, the placement is designed for the reader to read different tags in each detectable direction. The system estimates the direction from tags that could be read by the reader. The proposed system was actually implemented by using passive RFID devices operating at 13.56MHz, and the performance of the system was evaluated in a realistic environment. The result of experiments indicates that the proposed system could distinguish eight directions within 9cm.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a new congestion control scheme for high-speed packet communication networks. The basic idea of the scheme is to adopt a game theory called Minority Game (MG) to realize a selective reduction of transmission speed of the senders. MG is known to have a remarkable property such that the number of winners converges to a half of the number of players in spite of the selfish behavior of the players. By using such property of MG, we can realize a fair reduction of the transmission speed, which is more efficient than previous schemes in which all senders uniformly reduce their transmission speed. From the result of simulation, we could improve the efficiency of those schemes, especially when the bandwidth of the underlying network is very large.

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Other Link： http://id.nii.ac.jp/1001/00046025/

Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a new class of parallel branch-and-bound (B & B) schemes. The main idea of the scheme is to focus on the functional parallelism instead of conventional data parallelism, and to support such a heterogeneous and irregular parallelism by using a collection of autonomous agents distributed over the network. After examining several implementation issues, we describe a detail of the prototype system implemented over eight PC's connected by a network. The result of experiments conducted over the prototype system indicates that the proposed parallel processing scheme significantly improves the performance of the underlying B & B scheme by adaptively switching exploring policies adopted by each agent participating to the problem solving.

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we propose a new method to enhance the fault-tolerance of the Content Addressable Network (CAN), which is known as a typical pure P2P system based on the notion of Distributed Hash Table (DHT). The basic idea of the proposed method is to introduce redundancy to the management of index information distributed over the nodes in the given P2P network, by allowing each index to be assigned to several nodes, which was restricted to be one in the original CAN system. To keep the consistency among several copies of indices, we propose an efficient synchronization scheme based on the notion of labels assigned to each copy in a distinct manner. The performance of the proposed scheme is evaluated by simulation. The result of simulations indicates that the proposed scheme significantly enhances the fault-tolerance of the CAN system.

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

Content-Addressable Network (CAN) provides a mechanism that could retrieve objects in a P2P network by maintaining indices to those objects in a fully decentralized manner. In the CAN system, index caching is a useful technique for reducing the response time of retrieving objects. The key points of effective caching techniques are to improve cache hit ratio by actively sharing caches distributed over the P2P network with every node and to reduce a maintenance and/or routing overhead for locating the cache of a requested index. In this paper, we propose a new caching technique based on the notion of proxy-type caching techniques which have been widely used in WWW systems. It can achieve active cache sharing by incorporating the concept of proxy caching into the index access mechanism and locate a closer proxy cache of a requested index with a little routing overhead. By the result of simulations, we conclude that it can improve the response time of retrieving indices by 30% compared with conventional caching techniques.

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Language：English   Publisher：Information Processing Society of Japan (IPSJ)  

This paper proposes and evaluates a new class of parallel branch-and-bound (B&B) schemes. The main idea of the scheme is to focus on the functional parallelism instead of conventional data parallelism, and to support such a heterogeneous and irregular parallelism by using a collection of autonomous agents distributed over the network. After examining several implementation issues, we describe a detail of the prototype system implemented over eight PC's connected by a network. The result of experiments conducted over the prototype system indicates that the proposed parallel processing scheme significantly improves the performance of the underlying B&B scheme by adaptively switching exploring policies adopted by each agent participating to the problem solving.

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Other Link： http://id.nii.ac.jp/1001/00046042/

Language：English   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we proposed a new routing protocol for mobile ad-hoc wireless networks. The proposed protocol is a proactive routing protocol based on Q-routing for autonomously adapting the routing to mobility and topological change inherent in mobile ad-hoc wireless networks. It learns the task of finding an optimal routing policy on the underlying network while unsupervised and constructs a routing table on each host as the learning result. By using the routing table, the delivery of packets can be realized through the appropriate route according to the current network state. Furthermore, we implement the proposed protocol on NS-2 simulator and show the result of several experiments by using it.

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Other Link： http://id.nii.ac.jp/1001/00046061/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In recent years, Distributed Hash Table (DHT) has received considerable attentions as a tool for the resource management in pure P2P systems. In this paper, we will focus on the efficient processing of compound queries such as conjunctive and disjunctive queries, that should be issued by the users of P2P systems but has not been supported by conventional DHT-based schemes. The proposed method is based on the notion of result cache, that tries to cache a partial result of compound queries for the future use. T, he efficiency of the proposed method is evaluated by simulations.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a new localization scheme for wireless sensor networks, consisting of a huge number of sensor nodes equipped with wireless communication devices such as wireless LAN and Bluetooth. The proposed scheme is based on the PIT algorithm proposed by He et al. in 2003. The proposed scheme is actually implemented by using Bluetooth devices, and its performance is evaluated in a real environement.

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Other Link： http://id.nii.ac.jp/1001/00023263/

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a caching technique in Content-Addressable Network (CAN) which provides a mechanism for managing and retrieving shared objects distributed over a P2P network by maintaining their indices in a decentralized manner. The proposed technique improves the response time required for retrieving objects by caching indices at the participating nodes. More concretely, the proposed technique locates caches in a deterministic manner to realize an efficient cache location mechanism in the P2P network, and it achieves high hit ratio from the caches, while minimizing the overhead of finding locations. By the result of simulations, we conclude that it can improve the response time by 30% compared with conventional techniques.

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Other Link： http://id.nii.ac.jp/1001/00046098/

In recent years, wireless network devices spread and it is possible also not only on indoor such as home and office but the outdoors to make network connection using these devices. By using wireless network devices, the structure that the terminals gather and constitute temporary network autonomously is proposed, such as ad-hoc network Thus, many systems using the characteristic of the wireless network that the fixed network does not have are considered. In this paper, we propose wireless Peer-to-Peer system using the wireless multi-hop network to access wireless hot spot. In the neighborhood of the hot spot, when terminals form wireless multi-hop network, it becomes possible to connect to the Internet also for terminals that exist outside the radio wave attainment area of the hot spot. In addition, we propose the scheme to select the appropriate wireless hot spot in the case that there are some available wireless hot spots.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

Combinatorial auctions have received significant attention in recent years as new type auctions. The winner determination problem in the combinatorial auction is known to be NP-hard. In this paper, we propose a parallel branch and bound system for solving the problem in a short computation time. The basic idea of the proposed system is to design an efficient data structure of the search tree, and to adopt a peer-to-peer style for parallel processing. The result of experiments implies that the proposed system can provide stable performance for several instances compared with the traditional master-worker style system.

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Other Link： http://id.nii.ac.jp/1001/00046107/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, we propose a proxy caching algorithm for location-dependent data retrieval system. The proposed algorithm improves replacement performance by making use of the continuity information on the addressing scheme of location-dependent data, other than only the locality information used in the well-known Least Frequently Used (LFU) algorithm. The result of experiments conducted on a prototype system implies that the proposed algorithm can improve the response time by 20% compared with conventional algorithms.

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Other Link： http://id.nii.ac.jp/1001/00046106/

Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we propose load balancing techniques for dynamic system configurations in CAN (Content-Addressable Network). CAN provides the scalable information retrieval mechanism which makes use of distributed decentralized indexes in Pure P2P systems. The proposed method maintains the decentralized indexes when a peer participates in CAN, in such a way that it balances the load of each peer for processing index accesses. The result of simulations implies that the proposed method can improve the response time by 25% compared with the conventional method.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we propose an anonymous index access method in CAN (Content-Addressable Network). In CAN, the scalable information retrieval mechanism is achieved by making and accessing distributed decentralized indexes for shared contents in Pure P2P systems. The objective of the proposed method is to allow a peer to access an index in CAN networks in such a way that nobody can determine the peer's identity. More concretely, in order to preserve the anonymity, it uses a set of relay peers which are selected randomly to communicate with the target peer. We evaluate the anonymity and the communication cost of the proposed method by simulations.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

This paper reports the result of performance evaluation of a multiprocessor scheduler HMSS by using the standard task graph set STG. HMSS is an optimization scheduler based on the branch-and-bound method, and adopts a novel technique to calculate a sharp lower bound in an efficient manner. The result of experiments implies that 90% of the instances could be solved within 10 seconds, which contains two instances that could not be solved within one hour under conventional methods.

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Other Link： http://id.nii.ac.jp/1001/00046128/

Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

The improvement of mobile computing technologies makes it possible for mobile hosts to acquire information, e.g.location dependent information and personal information. We aim at the implementation of a system software on which mobile hosts can share the information with other hosts. Our proposed system provides a mechanism which can identify hosts by geographic location. An important issue for specifying mobile hosts by geographic location is the overhead of updating their location information. In this paper, we describe a design of our system that presents a location management mechanism to overcome the overhead. Moreover, we build the prototype of our proposed system that cooperate with some location management hosts, and illustrate effectiveness of our proposed system through a experiment.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

We propose a new scheduling method that can simultaneously achieve two main goals of task scheduling in distributed parallel systems ; i.e., to minimize the execution time of a parallel job without disturbing the execution of other jobs. We challenge to achieve those goals by introducing a new scheduler, called active scheduler, that controls the priority of parallel programs dynamically and balances the workload of computers, depending on the current status of runtime environment. Priority of parallel programs is controlled by controlling the concurrency of the programs. In this paper, we describe the implementation of a prototype system and evaluate the effectiveness of active scheduler under various conditions. The results of experiments imply that the overhead of introducing active scheduler is bounded by 15% of the original execution time, and it is in fact effective to adjust the execution of parallel programs to an actual distributed parallel processing environment in which many users execute their jobs at the same time.

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Other Link： http://id.nii.ac.jp/1001/00046163/

Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

The rapidly expanding technology of ITS (Intelligent Transport Systems) and wireless data networks recently has given mobile users the capability of accessing networks while roaming. But the instability of wireless communication lowers the communication efficiency seriously. In this paper, we propose a road vehicle communication system using location-aware buffer to provide location information efficiently to roaming users. In the system, we also propose a distribution method using the geographic access locality of location information to realize an efficient usage of location-aware buffers. Then we evaluate the performance of the proposed system and distribution method by doing a simulation on a model close to the realistic traffic roads environment.

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Language：English   Publisher：C S R E A PRESS  

Mobile hosts can acquire location-dependent information at any place and be connected to a network from anywhere with wireless communication devices such as cellular phones, wireless LAN, and so on. In such an environment, we aim at the implementation of the system software on which mobile hosts can share the location-dependent information with other hosts. It is, however, difficult for users that request location-dependent information to identify mobile hosts that provide them because the system presents no mechanism to identify hosts by the geographic location. In this paper, we propose location management system that can manage locations of mobile hosts and can identify them by the geographic location. Since our system is supposed under mobile computing environment, it has the mechanism that reduces the overhead of location management on wireless communication. Moreover, we implement a part of this system and show that this system is suitable for mobile environment through the experiment.

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Language：English   Publisher：IEEE COMPUTER SOC  

We designed and built an information announcement basic software system that realizes a new using style, called the TAM. This style regards a mobile computer as a server as well as a client. bl order to effectively announce information from a mobile computer as a server, the system uses stationary computers, called SMHs, that manages mobile computers. The effectiveness of the system has been shown. The system works well and gives a useful environment to clients. In the system, however, communications between a client and a server are always done via the SMH computer associated with the server This communication path is redundant in some cases. The server cannot provide high quality services to the client because of the redundancy In this paper, we design a new information announcement system, called the WOR, which is expansion of the TAM to solve the problem of the redundant path. In the WOR, we assume that a SMH is located at ever): network domain. The communication method uses two types of the SMH; Home SMH (HSMH) and Foreign SMH (FSMH). The HSMH is the same as the SMH in the TAM. The FSMH finds a shorter path for the mobile computer to provide the service to a client We show the system a useful mobile computing environment to clients through implementing the system.

DOI： 10.1109/ISADS.2001.917418

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Language：English   Publisher：IEEE COMPUTER SOC  

We designed and built an information announcement basic software system that realizes a new using style, called the TAM. This style regards a mobile computer as a server as well as a client. bl order to effectively announce information from a mobile computer as a server, the system uses stationary computers, called SMHs, that manages mobile computers. The effectiveness of the system has been shown. The system works well and gives a useful environment to clients. In the system, however, communications between a client and a server are always done via the SMH computer associated with the server This communication path is redundant in some cases. The server cannot provide high quality services to the client because of the redundancy In this paper, we design a new information announcement system, called the WOR, which is expansion of the TAM to solve the problem of the redundant path. In the WOR, we assume that a SMH is located at ever): network domain. The communication method uses two types of the SMH; Home SMH (HSMH) and Foreign SMH (FSMH). The HSMH is the same as the SMH in the TAM. The FSMH finds a shorter path for the mobile computer to provide the service to a client We show the system a useful mobile computing environment to clients through implementing the system.

DOI： 10.1109/ISADS.2001.917418

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Language：English   Publisher：IEEE COMPUTER SOC  

In this paper, we propose a new scheduling method that can simultaneously achieve two main goals of task scheduling in distributed parallel systems; i.e., to minimize the execution time of a parallel job without disturbing the execution of other jobs. We challenge to achieve those goals by introducing a new scheduler, called active scheduler, that controls the priority of parallel programs dynamically and balances the workload of computers, depending on the current status of runtime environment. Priority of parallel programs is controlled by controlling the concurrency of the programs, We implemented a prototype system to evaluate the effectiveness of active scheduler. The results of experiments imply that the overhead of introducing active scheduler is bounded by 15 % of the original execution time, and it is in fact effective to adjust the execution of parallel programs to an actual distributed parallel processing environment in which many users execute their jobs at the same time.

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Language：English   Publisher：C S R E A PRESS  

Mobile hosts can acquire location-dependent information at any place and be connected to a network from anywhere with wireless communication devices such as cellular phones, wireless LAN, and so on. In such an environment, we aim at the implementation of the system software on which mobile hosts can share the location-dependent information with other hosts. It is, however, difficult for users that request location-dependent information to identify mobile hosts that provide them because the system presents no mechanism to identify hosts by the geographic location. In this paper, we propose location management system that can manage locations of mobile hosts and can identify them by the geographic location. Since our system is supposed under mobile computing environment, it has the mechanism that reduces the overhead of location management on wireless communication. Moreover, we implement a part of this system and show that this system is suitable for mobile environment through the experiment.

Web of Science

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Language：English   Publisher：IEEE COMPUTER SOC  

In this paper, we propose a new scheduling method that can simultaneously achieve two main goals of task scheduling in distributed parallel systems; i.e., to minimize the execution time of a parallel job without disturbing the execution of other jobs. We challenge to achieve those goals by introducing a new scheduler, called active scheduler, that controls the priority of parallel programs dynamically and balances the workload of computers, depending on the current status of runtime environment. Priority of parallel programs is controlled by controlling the concurrency of the programs, We implemented a prototype system to evaluate the effectiveness of active scheduler. The results of experiments imply that the overhead of introducing active scheduler is bounded by 15 % of the original execution time, and it is in fact effective to adjust the execution of parallel programs to an actual distributed parallel processing environment in which many users execute their jobs at the same time.

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Language：Japanese   Publisher：一般社団法人情報処理学会  

In recent years, ITS (Intelligent Transport System) have been researched in order to prevent traffic accidents and relieve traffic congestion. Information on surrounding area of a vehicle is very important for neighboring vehicles. The information can be used to prevent traffic accidents and relieve traffic congestion. The inter-vehicle communication is more suitable to transmit the information than communication using infrastructures. The inter-vehicle commmunication, however, has the problem of an increase in packets because the communication employs Ad Hoc Network and uses broadcasting. ...

CiNii Books

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In recent years, the performance of mobile computers is improved and several information announcement systems for mobile computers are proposed. It is easy to take mobile computers and to get many kinds of information at the places. Since mobile computers can connect to a network any places, it is possible to announce the information in real time from them. It is, however, difficult to get information on some place from a mobile computer located at the place because there is no way to identify mobile computer by geographic location. It is possible to manage locations of mobile computers by using GPS and PHS. In this paper, we propose a decision method of location information and communication protocol, and a system in which a function realizing the method is appended to "Toolkit for mobile information announcement". Moreover, we present examples of service applications on our proposed system.

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Other Link： http://id.nii.ac.jp/1001/00044096/

Language：Japanese   Publisher：一般社団法人情報処理学会  

A current mobile communication method used on mobile hosts to receive data is an ondemand method, such as a cellular phone and PHS. Meanwhile, high performance S-band digital satellite or digital terrestrial broadcasting for mobile hosts will be available in a few years. In this research, we propose a new communication method to make use of data broadcasting and on-demand communication simultaneously, instead of conventional individual techniques. In this paper, we discuss a synchronization issue to transmit broadcast and on-demand data separately, and design at efficient system for multipl...

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Language：English   Publisher：SPRINGER-VERLAG BERLIN  

A mobile information announcement system has been constructed. In the system, a mobile computer can announce information at any place and any time. Moreover, the bandwidth problem between a mobile computer and an access point is pointed out. If the bandwidth of the network is narrow, all requests from clients cannot be processed by a mobile computer. An announcement mechanism for a mobile computer, which can effectively announce information with a narrow bandwidth network, is proposed. In this paper, in order to optimize performance of the proposed mechanism, parameters of the mechanism are analyzed in two kinds of networks through experiments. By optimizing parameters, the performance of the mechanism improves about 40% on wireless LAN compared with the performance without consideration of jitters in communication.

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Language：English   Publisher：C S R E A PRESS  

This paper proposes a mobile information announcement system dealing with network connectivity. Since traditional network: applications are not designed for mobile computers regarded as servers, stable services from mobile computers cannot be provided. In the system, a mechanism which can resolve problems of network connectivity (such as disconnections from networks and connections with low quality network) is provided in order for mobile computers to be able to provide services adequately. The system can also adapt to a, wide variety of network applications for a mobile announcement environment smoothly.

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Language：English   Publisher：C S R E A PRESS  

This paper proposes a mobile information announcement system dealing with network connectivity. Since traditional network: applications are not designed for mobile computers regarded as servers, stable services from mobile computers cannot be provided. In the system, a mechanism which can resolve problems of network connectivity (such as disconnections from networks and connections with low quality network) is provided in order for mobile computers to be able to provide services adequately. The system can also adapt to a, wide variety of network applications for a mobile announcement environment smoothly.

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Language：English   Publisher：C S R E A PRESS  

This paper proposes a mobile information announcement system dealing with network connectivity. Since traditional network: applications are not designed for mobile computers regarded as servers, stable services from mobile computers cannot be provided. In the system, a mechanism which can resolve problems of network connectivity (such as disconnections from networks and connections with low quality network) is provided in order for mobile computers to be able to provide services adequately. The system can also adapt to a, wide variety of network applications for a mobile announcement environment smoothly.

Web of Science

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Language：English   Publisher：SPRINGER-VERLAG BERLIN  

A mobile information announcement system has been constructed. In the system, a mobile computer can announce information at any place and any time. Moreover, the bandwidth problem between a mobile computer and an access point is pointed out. If the bandwidth of the network is narrow, all requests from clients cannot be processed by a mobile computer. An announcement mechanism for a mobile computer, which can effectively announce information with a narrow bandwidth network, is proposed. In this paper, in order to optimize performance of the proposed mechanism, parameters of the mechanism are analyzed in two kinds of networks through experiments. By optimizing parameters, the performance of the mechanism improves about 40% on wireless LAN compared with the performance without consideration of jitters in communication.

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Language：Japanese   Publisher：一般社団法人情報処理学会  

CiNii Books

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Language：Japanese  

CiNii Books

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Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

With the advance of computer technologies, mobile computers can hold many local resources in themselves. In many cases it is impossible to announce local resources on them because almost information announcement systems are not designed for them. In this paper, an information announcement system for mobile computers based on WWW is proposed. The system efficiently announces resources on mobile computers independently of whether they are connected to a network or nor, and wherever they are connected. The system can also select suitable announcement methods according to the type of resources. We implement a prototype of proposed system and evaluate it. The result of evaluation confirms effectiveness of the proposed system.

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Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

With the advance of computer technologies, mobile computers can hold many local resources in themselves. In many cases it is impossible to announce local resources on them because almost information announcement systems are not designed for them. In this paper, an information announcement system for mobile computers based on WWW is proposed. The system efficiently announces resources on mobile computers independently of whether they are connected to a network or nor, and wherever they are connected. The system can also select suitable announcement methods according to the type of resources. We implement a prototype of proposed system and evaluate it. The result of evaluation confirms effectiveness of the proposed system.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

Today, the WWW(World Wide Web) can be used to transmit multimedia data to the world.We have proposed the system which uses the WWW to transmit them from mobile computers.In this paper, we propose a new cache system which can cache layered multimedia data on the WWW server in order to deal with low bandwidth or disconnection between a mobile computer and the server.The cache system has the capability of providing with users the part of data which has the lowest quality even if a mobile computer is connected through low bandwidth communication pathes or disconnected.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, the bandwidth problem between a mobile computer and an access point is pointed out, and the cache update method, which can make the best of the limited bandwidth, is proposed. If there is not sufficient bandwidth, the mobile computer cannot announce all resources, and cannot update all caches on fixed computers. To satisfy client's requests with given bandwidth as much as possible, properties of resources are used actively. The proposed method limits traffic of storage type resources in order to announce non-storage type resources prior to storage type resources. Limitation on traffic is realized by limiting the number of connections for announcing storage type resources.

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

In this paper, the bandwidth problem between a mobile computer and an access point is pointed out, and the cache update method, which can make the best of the limited bandwidth, is proposed. If there is not sufficient bandwidth, the mobile computer cannot announce all resources, and cannot update all caches on fixed computers. To satisfy client's requests with given bandwidth as much as possible, properties of resources are used actively. The proposed method limits traffic of storage type resources in order to announce non-storage type resources prior to storage type resources. Limitation on traffic is realized by limiting the number of connections for announcing storage type resources.

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Language：English   Publisher：IEEE COMPUTER SOC  

In this paper the bandwidth problem between a mobile computer and art access point is pointed out, and a copy update mechanism, which carr make the best use of the limited bandwidth, is proposed. if the bandwidth of a network is not sufficient, a mobile computer cannot announce all resources, and cannot update some copies on fixed computers. To satisfy client's requests with given bandwidth as much as possible, the proposed mechanism limits traffic of storage type resources in order to announce non-storage type resources prior to storage type resources. Traffic is controlled by limiting the number of concurrent update operations for announcing storage type resources. We implement the prototype and evaluate it. The results show that it can stably announce non-storage type resources.

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Language：English   Publisher：IEEE COMPUTER SOC  

With the advance of computer technologies, mobile computers can hold many local resources in themselves. In many cases it is impossible to announce local resources an them because almost information announcement systems are not designed for them. In this paper, an information announcement system for mobile computers based on WWW is proposed. The system efficiently announces resources on mobile computers independently of whether they are connected to a network or not, and wherever they are connected. The system can also select suitable announcement methods according to the type of resources. We implement a prototype of proposed system and evaluate it. The result of evaluation confirms effectiveness of the proposed system.

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Language：English   Publisher：IEEE COMPUTER SOC  

With the advance of computer technologies, mobile computers can hold many local resources in themselves. In many cases it is impossible to announce local resources an them because almost information announcement systems are not designed for them. In this paper, an information announcement system for mobile computers based on WWW is proposed. The system efficiently announces resources on mobile computers independently of whether they are connected to a network or not, and wherever they are connected. The system can also select suitable announcement methods according to the type of resources. We implement a prototype of proposed system and evaluate it. The result of evaluation confirms effectiveness of the proposed system.

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Language：English   Publisher：IEEE COMPUTER SOC  

With the advance of computer technologies, mobile computers can hold many local resources in themselves. In many cases it is impossible to announce local resources an them because almost information announcement systems are not designed for them. In this paper, an information announcement system for mobile computers based on WWW is proposed. The system efficiently announces resources on mobile computers independently of whether they are connected to a network or not, and wherever they are connected. The system can also select suitable announcement methods according to the type of resources. We implement a prototype of proposed system and evaluate it. The result of evaluation confirms effectiveness of the proposed system.

Web of Science

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Language：Japanese   Publisher：Information Processing Society of Japan (IPSJ)  

A mobile computer can provide its resources for clients on a network at anytime and from anyplace, if there is an information announcement system which announces resources on the mobile computer independently of whether it is connected to the network or not, and wherever it is connected. In this paper, we discuss problems of the method, which update copies of storage type resources on a mobile computer, used in the previous proposed information announcement system, and propose the new update method to solve them. The proposed method changes update time according to the status of traffic issued from the mobile computer.

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J-GLOBAL

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Language：English   Publisher：I E E E  

We tried to construct a system in which we can enquire unknown words, included in TV news speech by repeating them spontaneously For example, we hear ''Japan would join PKO.'' from TV news and if ''PKO'' is an unknown word, then we can enquire it by saying ''What's the PKO?'' The system recognizes the word ''PKO'' and explains its meaning. In this system, it estimates a common section between announcer's speech and user speech, and recognizes the word corresponding to the common section. We solved a problem of speaker difference in extracting common sections by speaker subspace projection.

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Language：English   Publisher：I E E E  

Web of Science

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Language：English   Publisher：I E E E  

We tried to construct a system in which we can enquire unknown words, included in TV news speech by repeating them spontaneously For example, we hear ''Japan would join PKO.'' from TV news and if ''PKO'' is an unknown word, then we can enquire it by saying ''What's the PKO?'' The system recognizes the word ''PKO'' and explains its meaning. In this system, it estimates a common section between announcer's speech and user speech, and recognizes the word corresponding to the common section. We solved a problem of speaker difference in extracting common sections by speaker subspace projection.

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Language：English   Publisher：I E E E  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In practical speech recognition, it is required to recognize precisely the speech spoken by many speakers. But it is a difficult problem, because of difference among speakers. To this problem, we constructed the speaker subspace for individual speaker by subspace method. Our idea is that speaker subspace stands for speaker characteristics, and projected data to the subspace represent the phonetic information. Through this method we separate speaker information from phonetic information included in speech data. Speaker-independent, HMM was constructed using the separated phonetic information. Conventional speaker-independent HMM ignores the existence of the speaker subspaces and gathers speech data in the observation space. This causes the problem that the probability distribution of the HMM becomes flat, and then causes recognition errors. In this paper, we describe the result of phoneme recognition experiments using the speaker-independent HMM which was constructed by speech data in the speaker subspace.

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