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ABSTRACT: In order to increase the time connected to already deployed 802.11 wireless networks while traveling by subway in Tokyo, we have developed a system equipped with two scanning modes: 1) passively scanning on a selected channel, and 2) scanning with multiple open authentication. Through analysis and experiments, we have shown that our method increases the time connected to 802.11 wireless networks by establishing wireless connection when coming out of non-coverage area in the tunnel and switching its wireless connection across overlapping coverage area at station with less delay.
04/2010; , ISBN: 978-953-307-091-9
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JIP. 01/2010; 18:147-163.
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Proceedings of the 7th International Conference on Embedded Networked Sensor Systems, SenSys 2009, Berkeley, California, USA, November 4-6, 2009; 01/2009
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Proceedings of the 7th International Conference on Embedded Networked Sensor Systems, SenSys 2009, Berkeley, California, USA, November 4-6, 2009; 01/2009
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Proceedings of the 6th International Conference on Embedded Networked Sensor Systems, SenSys 2008, Raleigh, NC, USA, November 5-7, 2008; 01/2008
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ABSTRACT: In the ubiquitous computing environment, the physical locations of persons and goods are extremely important information. In this paper, the design of a fully distributed localization system based on ultrasound, mainly for the indoor environment, is described. This system performs localization with as few positioning references as possible by an iterative technique. When such a localization method is used, deterioration of localization accuracy due to no-line-of-sight signals and to accumulated errors is a problem. In this paper, the resolution of these problems is discussed and system evaluation by implementation experiments is carried out. With 24 devices, localization with an accuracy of about 20 cm is demonstrated. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(6): 17– 26, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20249
Electronics and Communications in Japan (Part III Fundamental Electronic Science) 02/2007; 90(6):17 - 26. · 0.14 Impact Factor
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1st Annual International Conference on Mobile and Ubiquitous Systems (MobiQuitous 2004), Networking and Services, 22-25 August 2004, Cambridge, MA, USA; 01/2004
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UbiComp 2004: Ubiquitous Computing: 6th International Conference, Nottingham, UK, September 7-10, 2004. Proceedings; 01/2004
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ABSTRACT: Smart" and "attentive" services using users' context are going to be realized in future ubiquitous computing environment. Sensor network is receiving considerable attention as one of the key technologies to keep track of the users' context in the real world. Conventional sensor network research mainly aimed at environmental monitoring. However requirements of the sensor network infrastructure for ubiquitous computing is different from the one for conventional environmental monitoring. We have developed a sensor network testbed named "U " to investigate issues that could arise when developing novel applications in a ubiquitous computing environment. U wireless sensor node that is capable of communicating with other nodes to carry sensing data and queries issued by users. In this paper we describe hardware and software architecture of U and present the performance evaluation of a sample application developed on U .
08/2003;
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ABSTRACT: In the future, huge amounts of embedded and invisible devices, as well as software components, will be connected to the Internet, and these "functional objects" are expected to play an important role in providing convenience services to users. In such a "ubiquitous Internet," users will be able to utilize various applications through functional objects anytime and anywhere. Since the ubiquitous Internet will be a highly dynamic, heterogeneous, and contextdependent environment, applications shotfid be able to change their functionality depending on dynamically changing user context. For example, when a user wishes to brows a PDF file on his small PDA display, a document-browsing application running on the PDA will need an additional transcoder function to reformat the PDF file. If the user wishes to use a voice-only device, such as a PDC (Personal Digital Cellular), to obtain information in the PDF document, the application will need to locate and use a PDF-to-text function as well as a text-to-voice function. Thus, to enable ubiquitous Internet applications to change their functionality on the fly, a mechanism capable of locating the appropriate functions transparently on the Internet is necessary. Generally, such locating mechanisms can be supported by a location-independent naming system.
04/2003;
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Comput. Syst. Sci. Eng. 01/2003; 18:3-6.
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1st IEEE Workshop on Software Technologies for Future Embedded Systems (WSTFES 2003), 15-16 May 2003, Hakodate, Hokkaido, Japan; 01/2003
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Real-Time and Embedded Computing Systems and Applications, 9th International Conference, RTCSA 2003, Tainan, Taiwan, February 18-20, 2003. Revised Papers; 01/2003
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ABSTRACT: Recently, with advances in differential GPS (DGPS) technology, the measurement performance of GPS has improved significantly. In this environment, degradation of the measurement performance of GPS due to multipath error that cannot be eliminated by the DGPS technique is a serious problem. In this paper, as a multipath solution in GPS, multipath estimation is carried out with an adaptive filter based on the least squares method. A method is presented to reduce the locking error in code phase locking and carrier phase locking by eliminating the multipath effect from the received signal correlation. Also, by means of computer simulation, the effectiveness of the present method is confirmed. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(1): 74–82, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1148
Electronics and Communications in Japan (Part I Communications) 09/2002; 86(1):74 - 82. · 0.19 Impact Factor
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ABSTRACT: This paper proposes significant route identification; the concept is to combine the locations acquired by the GPS module of the user's cellular phone. Significant routes are those that the user most frequently passes along. The proposal overcomes the two main weaknesses of cellular phones. One is that GPS data is acquired infrequently in order to reduce the phone's power consumption, and the other is the poor spatial accuracy of the cellular phone's commercial GPS module. In order to overcome these weaknesses, the proposed approach incrementally refines the stored routes whenever the user passes along them. In more detail, the system compares the newly acquired GPS points to the stored points and appends the new data so as to decrease route ambiguity. A experiment with 6 subjects over periods of 6-14 months demonstrates that the more often a user passes along a significant route, the more precisely the proposed approach can identify it.
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ABSTRACT: The realization of context-aware and recommendation ser-vice can be provided by acquiring and collecting the operation history of home appliances. In this paper, in order to collect operation information from DLNA certified devices, we propose a method using ARP spoofing called DLNA spoofing. We show that this method is effective to collect all detailed information in a home network. Also, DLNA spoofing has the better way for our research than the method using DLNA event notifi-cation function called GENA (Generic Event Notification Architecture). In GENA, we can collect only some simple information, nevertheless we cannot collect detailed information. On the other hand, by using our technique, we can collect all the information without changing the DLNA standard.
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ABSTRACT: With significant advancements in VLSI design and mass production, many ubiquitous computing services, which were once a dream, have become technically feasible. In light of this, context-awareness has become a fundamental concern. In order to provide context-aware services, a system should be able to identify contextual information, process it, and present it to context-aware applications. Thus in this paper, we present a contextual-data managing platform architecture, built specifically for this purpose. Recognizing the importance of providing an extensible world model, we propose a novel contextual managing and integrating architecture using components called Mappers. Having already implemented a prototype of this system in our laboratory, it is currently being used by researchers and visitors alike.
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ABSTRACT: Context-aware computing technologies provide great potential to help us adaptively reducing power consumption. We have proposed a context-aware power management system called Gynapse, which builds a three-level Hierarchical Hidden Markov Model (HHMM) to predict the exact usage of each device from multi-modal sensors, and then switches their power modes based on prediction to maximize the total energy saving under the constraint of user required response time. In this paper, we will discuss Gynapse's implementation in our laboratory and experimental results.
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ABSTRACT: The main objective of this paper is to summarize recent researches on energy efficiency of the Internet and pose several open challenges toward future energy-efficient network architecture. The rapid deployment of network-ready devices in the last decade has greatly contributed for enabling full-time access to a wide variety of services on the Internet. It is commonly recognized that required bandwidth will be increasing rapidly to support rich services such as IPTV for the next decade. On the other hand, global energy saving is a matter of public concern, and now there is a lot of interest in reducing energy consumption of IT systems. Guaranteeing full-time connectivity in the Internet is also power consuming. For mobile networks and wireless sensor networks, there are many researches on energy efficiency. How-ever, there is not much effort on reducing power consumption of wired networks. Office/home LAN switches, access networks and backbone networks are continuously consuming a lot of electric power. From this point of view, we summarize previous works on energy efficient networks to provide a bird's-eye view of the technology and discuss several open challenges to address the issue.
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ABSTRACT: This paper proposes a power saving system, called Smart Wireless Aggregation, that enables to reduce the power consumption of the access network infrastructure in the office environment. By taking advantage of the redundantly available wireless network to aggregate idling and low utilization users in the wireless network access switches can be turned off. The increases in delay and other negative effects such as the increased stress on devices due to repeatedly turning them on or off is handled through specific reconfiguration policies. In this paper we present the system design and performance analysis through simulations.
