[Show abstract][Hide abstract] ABSTRACT: For the efficient use of spectrum resource, it is important to understand spectrum occupancy at a high spatial resolution, so a large number of measurement locations are required. In this work, in order to increase measurement locations, we design and implement a low-end spectrum sensor which is capable of switching to different channels in a spectrum range of the UHF band. The spectrum sensor can provide intuitive knowledge for spectrum usage.
[Show abstract][Hide abstract] ABSTRACT: We present a wake-up wireless communication system, which can drastically reduce idle listening energy for long idle listening applications by using a wake-up wireless module. We consider chance encounter communication, which is communication during opportunistic encounters, as a long idle listening application. There are three requirements for applying the wake-up system to chance encounter communication: a group selective wake-up, a multiple group support, and small circuit size. In order to achieve these three requirements, we introduce Bloom-filter-based ID matching to the wake-up wireless module. The present paper describes the design of the wake-up module using a Bloom-filter-based ID matching mechanism. We evaluate the proposed module by performing circuit-level simulations. The simulation results show that the proposed system can reduce listening power by a factor of 1,000 to 10,000 compared to conventional Wi-Fi modules.
Information and Telecommunication Technologies (APSITT), 2010 8th Asia-Pacific Symposium on; 07/2010
[Show abstract][Hide abstract] 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.
Radio Communications, 04/2010; , ISBN: 978-953-307-091-9
[Show abstract][Hide abstract] ABSTRACT: Power conservation has become a serious concern during people's daily life. Ubiquitous computing technologies clearly provide a potential way to help us realizing a more environment-friendly lifestyle. In this paper, we propose a ubiquitous power management system called Gynapse, which uses multi-modal sensors to predict the exact usage of each device, and then switches their power modes based on predicted usage to maximize the total energy saving under the constraint of user required response time. We build a three-level Hierarchical Hidden Markov Model (HHMM) to represent and learn the device level usage patterns from multi-modal sensors. Based on the learned HHMM, we develop our predictive mechanism in Dynamic Bayesian Network (DBN) scheme to pre- cisely predict the usage of each device, with user required response time under consideration. Based on the predicted usage, we follow a four-step process to balance the total energy saving and response time of devices by switching their power modes accordingly. We use PlaceLab data set to evaluate Gynapse, and the preliminary results demonstrate that Gynapse has the capability to reduce power consumption while keeping the response time not exceed user require- ment, which provides a complementary approach to previous power manage- ment systems.
Journal of Information Processing 01/2010; 18:147-163. DOI:10.2197/ipsjjip.18.147
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: With advances in sensor devices and networking technologies, it is expected that future networks will contain immense numbers of sensors that are capturing time-varying data. It is necessary to process queries over the data for analysis and to store the data for later use. For querying the data, data disorder is a common problem. Existing approaches use buffers to recover the order but there are problems in deciding buffer sizes and buffer residence times. To avoid these problems and to satisfy the need to store the data for later use, our approach writes indexed data rapidly to a stable disk. This approach, however, has a problem in that existing indexing methods are not up to the task; “sparse indexing” offers fast write-speeds but cannot handle disordered data, “dense indexing” can handle disordered data but its write-speed is inadequate. Our solution is a novel indexing method that can rapidly store slightly disordered time-series sensor data. Our proposal succeeds because it uses a novel data structure, “offset bitmaps”, to extend the sparse indexing method. The offset bitmaps provide pointers that can handle delayed data and so allow them to be managed efficiently. Experiments show that our method has several advantages over conventional alternatives. We verify that the proposed method has 10 times the write speed of the existing dense indexing method.
[Show abstract][Hide abstract] ABSTRACT: In this demonstration we present an ubiquitous health monitoring system based on the NGN/IMS (next generation network/IP multimedia subsystem). It enables us to be taken care of by medical professionals anytime, anywhere using portable medical sensors and mobile networks. To provide seamless health monitoring services, an open, secure and functional platform is required. Such a platform should support multiple functions such as real-time transfer, event notification, and continuous data accumulation. The NGN/IMS is a potential platform to fulfill these requirements, because it is a standard- based open platform, which provides AAA (authentication, authorization and accounting), QoS (quality of service) support, event notification and a data management server. We present a system design and a prototype implementation on a NGN/IMS testbed.
[Show abstract][Hide abstract] ABSTRACT: Due to people!s concern for a healthy life, there is a rising need for a health monitoring available anytime and anywhere. We present an ubiquitous health monitoring system based on the NGN/IMS (next generation network/IP multimedia subsystem) and proper data format design for ubiquitous health monitoring system.
[Show abstract][Hide abstract] ABSTRACT: In distributed spectrum sensing, we deploy ten thousands of sensor nodes, and a low-cost sensor node is necessary. In this work, we design the sensor node specialized in power level measurement for distributed spectrum sensing, and we discuss 3 components of the node, which are frequency range, RBW and a detector.
Proceedings of the 7th International Conference on Embedded Networked Sensor Systems, SenSys 2009, Berkeley, California, USA, November 4-6, 2009; 01/2009
[Show abstract][Hide abstract] ABSTRACT: Excessive power consumption is a major problem in wireless communication. This is particularly true in ubiquitous computing environments, since wireless devices consume a considerable amount of energy in idle listening. Wake-up wireless communication technology is a promising candidate for reducing power consumption during idle listening. To realize wake-up wireless communication, this paper proposes a novel ID matching mechanism that uses a Bloom filter. This paper describes the design and implementation of a wireless wake-up module that uses this ID matching mechanism. Simulation results reveal that the wake-up module consumes only 12.4 muW while idle listening, and that employing this Bloom-filter-based approach eliminates 99.95 % of power consumption in our application scenarios.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: Radio spectrum has turned into a precious natural re-source from free goods due to the rapid development of wire-less communication technology. In order to efficiently utilize radio spectrum, a spectrum policy should be enough appro-priate to create new industries and new technologies. From this point of view, we have developed a distributed spectrum sensing system which collects dense information of spec-trum usage over large area. In this paper, we discuss the requirements and the design of the distributed spectrum sens-ing system.
[Show abstract][Hide abstract] ABSTRACT: This paper proposes a stochastic scheme called Gynapse which balances power saving and response time by switching electronic devices between dierent power modes. Gynapse predicts the wake-up probability of each device on the basis of a Hierarchical Hidden Markov Model. With the predicted probability, required response time, and de- vice power consumption as inputs, Gynapse uses our novel optimization method to manage power mode switching, and thereby minimizes total energy consumption while ensuring response time does not exceed the required level.
[Show abstract][Hide abstract] ABSTRACT: Radio spectrum has turned into a precious natural resource from free goods due to the rapid development of wireless communication technology. In order to efficiently utilize radio spectrum, a spectrum policy should be enough appropriate to create new industries and new technologies. From this point of view, we have developed a distributed spectrum sensing system which collects dense information of spectrum usage over large area. In this work, we discuss the requirements and the design of the distributed spectrum sensing system.
Proceedings of the 7th International Conference on Embedded Networked Sensor Systems, SenSys 2009, Berkeley, California, USA, November 4-6, 2009; 01/2009
[Show abstract][Hide abstract] ABSTRACT: The problem of idle listening is one of the most significant sources of energy consumption in wireless sensor nodes, and many techniques have been proposed based on duty cycling to reduce this cost. In this paper, we present a new asynchronous ...
Proceedings of the 6th International Conference on Embedded Networked Sensor Systems, SenSys 2008, Raleigh, NC, USA, November 5-7, 2008; 11/2008
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present a method for estimation of objects' positions and orientations in an indoor environment. For ubiquitous computing, it is important to realize provision of a location-aware information service for humans. Especially, orientation information can reflect a more detailed context than that obtained merely according to a location: people standing face-to-face or back-to-back have vastly different contexts. We are tackling indoor location and orientation estimation using a new approach called topological estimation, which specifically examines relative relationships of humans rather than their absolute positions. In the initial implementation of topological estimation, we have used infrared tags as sensors to collect real-world related information. This paper describes an ultrasonic and radio device system to collect objects' local relationships.
Mobile Adhoc and Sensor Systems, 2007. MASS 2007. IEEE Internatonal Conference on; 11/2007
[Show abstract][Hide abstract] ABSTRACT: It is important for ubiquitous computing to realize providing location-aware information service for humans. Especially, orientation information can reflect a more detailed context than that obtained merely according to the location: people standing face-to-face or back-to-back would have vastly different contexts. We are tackling the indoor location and orientation estimation with a new approach called topological estimation that focuses on relative relationships of humans rather than their absolute positions. In the initial implementation of the topological estimation, we have used infrared tags as the sensors to collect real world relative information. However, there is a lower precision issue in the infrared system. To solve the issue, this paper proposes an ultrasonic system to provide higher sensing accuracy.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we introduce magic surfaces; a novel positioning and networking infrastructure for indoor sensor network applications. To support various kinds of applications, magic surfaces provide positioning, orientation estimation, bidirectional communication and power transmission functions in a contact-less manner by using a magnetic-based technique. This paper describes the design, implementation and performance evaluations of magic surfaces.
[Show abstract][Hide abstract] 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.
Electronics and Communications in Japan (Part I Communications) 03/2005; 88(3):63-75. DOI:10.1002/ecja.10177 · 0.19 Impact Factor