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Advance publication (published online immediately after acceptance)

Volume E89-D No.5  (Publication Date:2006/05/01)

    Special Section on Challenges in Ad-hoc and Multi-hop Wireless Communications
  • FOREWORD

    Koji NAKANO  Jacir L. BORDIM  Peter DAVIS  

     
    FOREWORD

      Page(s):
    1613-1613
  • A Localization Scheme for Sensor Networks Based on Wireless Communication with Anchor Groups

    Hiroyuki OCHI  Shigeaki TAGASHIRA  Satoshi FUJITA  

     
    PAPER

      Page(s):
    1614-1621

    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.

  • A Multiple-Layer Self-Organizing Wireless Network

    Hyunjeong LEE  Chung-Chieh LEE  

     
    PAPER

      Page(s):
    1622-1632

    A self-organizing wireless network has to deal with reliability and congestion problems when the network size increases. In order to alleviate such problems, we designed and analyzed protocols and algorithms for a reliable and efficient multiple-layer self-organizing wireless network architecture. Each layer uses a high-power root node to supervise the self-organizing functions, to capture and maintain the physical topology, and to serve as the root of the hierarchical routing topology of the layer. We consider the problem of adding a new root with its own rooted spanning tree to the network. Based on minimum-depth and minimum-load metrics, we present efficient algorithms that achieve optimum selection of root(s). We then exploit layer scheduling algorithms that adapt to network load fluctuations in order to optimize the performance. For optimality we consider a load balancing objective and a minimum delay objective respectively. The former attempts to optimize the overall network performance while the latter strives to optimize the per-message performance. Four algorithms are presented and simulations were used to evaluate and compare their performance. We show that the presented algorithms have superior performance in terms of data throughput and/or message delay, compared to a heuristic approach that does not account for network load fluctuations.

  • Branch Aggregation Multicast (BAM): An Energy Efficient and Highly Compatible Multicast Protocol for Wireless Sensor Networks

    Akihito OKURA  Takeshi IHARA  Akira MIURA  

     
    PAPER

      Page(s):
    1633-1643

    In this paper, we propose a multicast protocol, called BAM (Branch Aggregation Multicast), for wireless sensor networks. The main contribution of BAM is a reduction in the radio communication load, which is a key determinant of sensor energy consumption. BAM does not use any control packets such as join/leave messages and does not manage multicast groups. BAM is highly compatible with existing wireless sensor protocols, such as routing protocols, MAC protocols, and other kinds of energy efficient protocols. BAM implementation is quite simple and BAM works on various networks even if some sensors are not BAM-capable. BAM is composed of two aggregation techniques. One is single hop aggregation (S-BAM) and the other is multiple paths aggregation (M-BAM). S-BAM aggregates radio transmission within a single hop and enables single transmission to multiple intended receivers. M-BAM aggregates multiple paths into fewer ones and limits the range of radio transmission. S-BAM is designed to reduce redundant communication at every branch while M-BAM is designed to reduce the number of branches. SM-BAM, the combination of S-BAM and M-BAM, can reduce the radio communication load thus enabling energy efficient multicast communication. We evaluate BAM in three ways, qualitative evaluation by theoretical analysis, quantitative evaluation through computer simulations, and experiments using CrossBow's MICA2. Our results show that BAM is a very energy efficient multicast protocol that well supports wireless sensor networks.

  • The Enhancement on Communication Stability in MANETs with Unit Disk Graph Model

    Makoto TAKIZAWA  Hiroto AIDA  Masato SAITO  Yoshito TOBE  Hideyuki TOKUDA  

     
    PAPER

      Page(s):
    1644-1653

    In this paper, we present a novel forwarding scheme to enhance communication stability based on geographic routing in mobile ad hoc networks, which is called "Position-based Heuristic Forwarding" (PHF). For alternative solutions to traditional ad hoc routings, many geographic routing algorithms have been proposed. Most of the existing routings impose a certain restriction, planarity, on the graph structure of network for delivering messages to destination definitely. PHF achieves the guaranteed packet delivery over Unit Disk Graph, which is more widely employed graph model for the study of ad hoc networks. Accordingly, to eliminate the restriction of the routing algorithms enhances the probability to deliver messages successfully in networks with high nodes' mobility rate. In the simulation of PHF, we have evaluated the performance comparisons between PHF and its related work, Greedy Perimeter Stateless Routing (GPSR) and Dynamic Source Routing (DSR), which are the prominent geographic and conventional topology-based routing protocols, respectively. The results show that PHF provides higher packet delivery success rate indicating better communication stability and equal or less overhead than these work.

  • An Energy*Delay Efficient Multi-Hop Routing Scheme for Wireless Sensor Networks

    Trong Thua HUYNH  Choong Seon HONG  

     
    PAPER

      Page(s):
    1654-1661

    Sensors have very scarce resources in terms of memory, energy and computational capacities. Wireless sensor network is composed of a large number of such sensor nodes densely deployed in inhospitable physical environments. Energy efficient information dissemination throughout such a network is still a challenge. Though dissemination of information with minimum energy consumption is a key concern in wireless sensor networks, it often introduces additional delay. In this work, we first propose an energy and delay efficient multi-hop routing scheme called C2E2S (Cluster and Chain based Energy*Delay Efficient Routing Scheme) for wireless sensor networks. This scheme is a combination of cluster-based and chain-based approaches and the way to form clusters and chains in this work is center-based approach. To reduce a large number of communication overheads due to this approach, we propose a modified-center-based approach called passive-BS-based approach. Next, we propose (1) an energy and delay aware routing algorithm for sensors within each k-hop cluster, and (2) an Energy-efficient chain construction algorithm for cluster heads. To evaluate the appropriateness of our approach, we analyze the evaluated performance against existing protocols in terms of communication overhead, the number of communication rounds (network lifetime), total amount of energy dissipated in the system over time, network delay and Energy*Delay metric using SENSE simulator. The simulation results show that C2E2S consumes less energy, balances the energy and delay metrics, and extends the network lifetime as compared to other approaches.

  • Mobility-Awareness: An Efficient Approach to Improve Energy Efficiency in Location-Aware Computing

    MoonBae SONG  KwangJin PARK  Ki-Sik KONG  

     
    PAPER

      Page(s):
    1662-1671

    There are two principal aspects of "mobility" in location-aware computing: (1) how to support mobility and (2) how to exploit it. This paper considers the latter, while many existing works only concentrate on the former. This work is trying to prove that the performance of location-aware systems will be greatly improved by understanding the user's movement. In this paper, we propose a novel location update protocol called state-based location update protocol (SLUP), which significantly minimizes the energy consumption of mobile client by exploiting a syntactic information of a user's movement. This concept is called mobility-awareness which is a kind of context-awareness. Moreover, there are three variations of the proposed protocol in terms of how to choose the optimal state: SLUP/BS, SLUP/UITR, and SLUP/IUT<Tiut>. Experimental results show that the proposed protocol outperforms the well-known existing protocols such as dead-reckoning and distance-based protocol, and that the SLUP/IUT<Tiut> approach can achieve different performance tradeoffs between energy efficiency and location accuracy by fine-tuning its algorithmic parameter Tiut.

  • Dynamic Topology Control and Routing in Wireless Ad Hoc Networks

    Kwangil LEE  Kapdong KIM  

     
    LETTER

      Page(s):
    1672-1675

    In this letter we consider topology control and routing problem in wireless networks where equipped with point-to-point wireless links such as directional antennas or free space optics. In point-to-point wireless networks, each node has a limited number of transceivers and hence can communicate with only a limited number of nodes within its transmission range. The selection of the limited number of neighbors is very critical for the network performance. In this letter, we propose a topology control algorithms which consider the topology control and routing of each demand is considered simultaneously. For this, we introduce the degree constraint shortest path problem for finding optimal (shortest) paths in wireless point-to-point networks. Also, we propose two topology control algorithms: minimum hop (MHA) and resource availability ratio (RAR) algorithm. The resource availability ratio algorithm considers not only the available link bandwidth but also the available interfaces between neighbors. By simulation experiments, we compare the performance of each algorithm.

  • Non-saturated Throughput Analysis of IEEE 802.11 Ad Hoc Networks

    Changchun XU  Zongkai YANG  

     
    LETTER

      Page(s):
    1676-1678

    This letter presents a simple but accurate analytical model to evaluate the throughput of IEEE 802.11 distributed coordination function in non-saturated conditions. The influence of offered load on the throughput of both basic and RTS/CTS access mechanisms are analyzed and compared. It's shown that basic access scheme can achieve the same maximal throughput as that of RTS/CTS mechanism in non-saturated conditions while the latter is robust to the number of contending stations compared to basic mechanism. The analytical results are validated by extensive simulations.

  • Regular Section
  • A New Method for Low-Capture-Power Test Generation for Scan Testing

    Xiaoqing WEN  Yoshiyuki YAMASHITA  Seiji KAJIHARA  Laung-Terng WANG  Kewal K. SALUJA  Kozo KINOSHITA  

     
    PAPER-Dependable Computing

      Page(s):
    1679-1686

    Research on low-power scan testing has been focused on the shift mode, with little consideration given to the capture mode power. However, high switching activity when capturing a test response can cause excessive IR-drop, resulting in significant yield loss due to faulty test results. This paper addresses this problem with a novel low-capture-power X-filling method by assigning 0's and 1's to unspecified bits (X-bits) in a test cube to reduce the switching activity in capture mode. This method can be easily incorporated into any test generation flow, where test cubes can be obtained during ATPG or by X-bit identification. Experimental results show the effectiveness of this method in reducing capture power dissipation without any impact on area, timing, and fault coverage.

  • Proposal of Testable Multi-Context FPGA Architecture

    Kazuteru NAMBA  Hideo ITO  

     
    PAPER-Dependable Computing

      Page(s):
    1687-1693

    Multi-context FPGAs allow very quick reconfiguration by storing multiple configuration data at the same time. While testing for FPGAs with single-context memories has already been studied by many researchers, testing for multi-context FPGAs has not been proposed yet. This paper presents an architecture of testable multi-context FPGAs. In the proposed multi-context FPGA, configuration data stored in a context can be copied into another context. This paper also shows testing of the proposed multi-context FPGA. The proposed testing uses the testing for the traditional FPGAs with single-context. The testing is capable of detecting single stuck-at faults and single open faults which affect normal operations. The number of test configurations for the proposed testing is at most two more than that for the testing of FPGAs with single-context memories. The area overhead of the proposed architecture is 7% and 4% of the area of a multi-context FPGA without the proposed architecture when the number of contexts in a configuration memory is 8 and 16, respectively.

  • Framework for Personalized User Interface by Sharing User-Centric Context between Real and Virtual Environments

    Seiie JANG  Woontack WOO  

     
    PAPER-Human-computer Interaction

      Page(s):
    1694-1701

    In this paper, we propose a framework that provides users with personalized interfaces by sharing user-centric context between real and virtual environments. The proposed framework consists of ubi-UCAM for generating user's contexts, NAVER for managing virtual environment, and rv-Interface for linking ubi-UCAM with NAVER. Firstly, personalized interface helps users to concentrate on their tasks of interest by reducing burdensome menu selections according to user's context. In addition, user-adaptive contents based on user's preferences allow more pleasure personal experiences. Finally, personalized interface with context hand-over mechanism enables users to continuously interact with virtual environments, even if the users move around. According to experimental results, we expect that the proposed framework can play an important role for realizing user-centric VR applications by exploiting personalized interface that adapts to user-centric context.

  • A Mobile-Care System Integrated with Bluetooth Blood Pressure and Pulse Monitor, and Cellular Phone

    Ren-Guey LEE  Chun-Chieh HSIAO  Chun-Chung CHEN  Ming-Shiu LIU  

     
    PAPER-Human-computer Interaction

      Page(s):
    1702-1711

    Blood pressure is one of the most important indicators of human health condition. A patient with hypertension in long term tends to have various kinds of vessel pathological changes such as coronary heart disease, apoplexy, and nephropathy. Consequently, the blood pressure measurement is important in daily health care for hypertension patients. Traditionally, the design and implementation of blood pressure monitor mostly focuses on the accuracy of pressure measurement and does not deal with the requirement of hypertension health care services with two-way communication via instant messages between the patient and the medical center. In this paper, a mobile-care system integrated with Bluetooth blood pressure and pulse monitor, and cellular phone is designed and implemented to transmit the physiological parameters of the patient in real time via wireless networks. The health care provider can monitor the blood pressure, body temperature, and heart rate of the patient and provide services by intelligent health care systems. The intelligent system constantly manages the health care data and periodically reports the status of the patient to the patient's family members. By the above care mechanism, the patients with hypertension can easily obtain long-term and constant monitoring of the physiological parameters and thus better health care services. A questionnaire survey has been conducted among medical personnel in Taipei municipal Wang-Fang hospital to collect their opinions of using our proposed and implemented blood pressure monitor with Bluetooth transmission function. An average of 95% of the medical personnel agree that long-term monitoring of the patients' physiological information such as blood pressure can be helpful to reduce medical cost, to provide useful reference data, and to provide long-distance health care. This thus shows strong support of the usefulness of our proposed device. Our proposed and implemented device has also been submitted to US FDA for medical device approval.

  • Effects of Phoneme Type and Frequency on Distributed Speaker Identification and Verification

    Mohamed Abdel FATTAH  Fuji REN  Shingo KUROIWA  

     
    PAPER-Speech and Hearing

      Page(s):
    1712-1719

    In the European Telecommunication Standards Institute (ETSI), Distributed Speech Recognition (DSR) front-end, the distortion added due to feature compression on the front end side increases the variance flooring effect, which in turn increases the identification error rate. The penalty incurred in reducing the bit rate is the degradation in speaker recognition performance. In this paper, we present a nontraditional solution for the previously mentioned problem. To reduce the bit rate, a speech signal is segmented at the client, and the most effective phonemes (determined according to their type and frequency) for speaker recognition are selected and sent to the server. Speaker recognition occurs at the server. Applying this approach to YOHO corpus, we achieved an identification error rate (ER) of 0.05% using an average segment of 20.4% for a testing utterance in a speaker identification task. We also achieved an equal error rate (EER) of 0.42% using an average segment of 15.1% for a testing utterance in a speaker verification task.

  • A Relevance Feedback Image Retrieval Scheme Using Multi-Instance and Pseudo Image Concepts

    Feng-Cheng CHANG  Hsueh-Ming HANG  

     
    PAPER-Image Processing and Video Processing

      Page(s):
    1720-1731

    Content-based image search has long been considered a difficult task. Making correct conjectures on the user intention (perception) based on the query images is a critical step in the content-based search. One key concept in this paper is how we find the user preferred low-level image characteristics from the multiple positive samples provided by the user. The second key concept is how we generate a set of consistent "pseudo images" when the user does not provide a sufficient number of samples. The notion of image feature stability is thus introduced. The third key concept is how we use negative images as pruning criterion. In realizing the preceding concepts, an image search scheme is developed using the weighted low-level image features. At the end, quantitative simulation results are used to show the effectiveness of these concepts.

  • Human Foot Reconstruction from Multiple Camera Images with Foot Shape Database

    Jiahui WANG  Hideo SAITO  Makoto KIMURA  Masaaki MOCHIMARU  Takeo KANADE  

     
    PAPER-Image Recognition, Computer Vision

      Page(s):
    1732-1742

    Recently, researches and developments for measuring and modeling of the human body have been receiving much attention. Our aim is to reconstruct an accurate shape of a human foot from multiple camera images, which can capture dynamic behavior of the object. In this paper, a foot-shape database is used for accurate reconstruction of human foot. By using Principal Component Analysis, the foot shape can be represented with new meaningful variables. The dimensionality of the data is also reduced. Thus, the shape of object can be recovered efficiently, even though the object is partially occluded in some input views. To demonstrate the proposed method, two kinds of experiments are presented: reconstruction of human foot in a virtual reality environment with CG multi-camera images, and in real world with eight CCD cameras. In the experiments, the reconstructed shape error with our method is around 2 mm in average, while the error is more than 4 mm with conventional volume intersection method.

  • A Growth Model for Root Systems of Virtual Plants with Soil and Moisture Control

    Jijoon KIM  

     
    PAPER-Computer Graphics

      Page(s):
    1743-1750

    A realistic computer graphics (CG) model of root growth that accounts for the effects of soil obstruction and moisture variations is proposed. While the exposed parts of plants have been modeled extensively in CG, realistic root models have received little attention, and the potential effects of root characteristics on the growth of foliage has yet to be considered in detail. The proposed model represents roots as series of bend points and link points and defines the root systems as a layered structure formed by roots connected via link points. This approach allows for two general types of root systems based on branching probabilities of lateral and adventitious roots: main root systems consisting of a thick main root and thinner lateral roots, and fibrous root systems consisting of adventitious roots of relatively uniform diameter. The model also expresses the behavior of root growth in terms of hydrotropism, gravitropism, flexion and growth inhibition by assigning gravity, moisture and consistency parameters to underground voxels. The model is shown through simulations of various growth conditions to generate individualized root systems that reflect the growth environment and characteristics of the plant.

  • Surrogate Integrated PQRM and Its Replication Scheme in Wireless Grid

    Jeong-Je CHO  Yong-Hyuk MOON  Chan-Hyun YOUN  

     
    LETTER-Computer Systems

      Page(s):
    1751-1754

    Recently, the necessity of interconnection between wired Grid and wireless networks has grown up. In wireless Grid, an efficient resource management is essential in order to solve the problem of unreliability caused by intermittency of wireless since mission-critical service like e-Health is expected to be a main application in wireless Grid. In this letter, we consider replica management to provide a reliable resource management and computing, and propose Surrogate integrated PQRM (S-PQRM) architecture with cost adaptive replica management scheme. Through the theoretical analysis and simulation, we show a reliable and cost adaptive replica management scheme in aspects of reliability and cost performance within budget-constrained application.

  • Routing in Hexagonal Networks under a Corner-Based Addressing Scheme

    Huaxi GU  Jie ZHANG  Zengji LIU  Xiaoxing TU  

     
    LETTER-Networks

      Page(s):
    1755-1758

    In this letter, a new addressing scheme for hexagonal networks is proposed. Using the new addressing scheme, many routing algorithms designed for networks using square-based topologies such as mesh and torus can also be applied to hexagonal networks. Methods of applying the turn model to hexagonal networks are derived, with some new minimal and partial adaptive routing algorithms obtained. Simulations of the new routing algorithms under different working conditions are carried on hexagonal networks of various sizes. The results show that the proposed algorithms can offer lower packet delay and loss rate than the popular dimension order routing algorithm.

  • How Much Does Color Information Help Optical Flow Computation?

    Naoya OHTA  Satoe NISHIZAWA  

     
    LETTER-Image Recognition, Computer Vision

      Page(s):
    1759-1762

    Optical flow is usually computed only on the basis of intensity information of images. Therefore, if we use color information in addition to the intensity, it is expected that more accurate optical flow can be computed. However, this intuition will be correct only when the following conditions are satisfied. First, the images should contain rich color variations. Moreover, it is also required that the image gradient of each color band differs in its direction. In this report, we empirically examined the difference of gradient directions on each band using 500 images, and evaluated quantitatively the advantage of using color information for optical flow computation.

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