Masateru Minami

DOLPHIN: an autonomous indoor positioning system in ubiquitous computing environment

Determining physical location of indoor objects is one of the key issues in development of context-aware applications in ubiquitous computing environments. This is mainly because context information obtained from sensor networks is meaningful only when the physical location of the context information source is determined. Recently, several indoor location information systems, such as Active Bat and Cricket, have been developed for precise indoor object localization. However, to provide accurate physical location tracking in large-scale space, those systems requires a lot of manual configuration for all the ultrasonic sensor nodes. To reduce configuration costs, we developed a new indoor positioning system called DOLPHIN. The DOLPHIN system consists of distributed wireless sensor nodes which are capable of sending and receiving RF and ultrasonic signals. These nodes are attached to various indoor objects. And using a novel distributed positioning algorithm in the nodes, DOLPHIN enables autonomous positioning of the objects with minimal manual configuration. This paper describes the design and implementation of the DOLPHIN system, and evaluates basic performance through several experiments in an indoor environment.

DOLPHIN: A Practical Approach for Implementing a Fully Distributed Indoor Ultrasonic Positioning System

Obtaining indoor location information is one of the essential technologies for enriching various ubiquitous computing applications. Although many indoor location systems have been proposed until now, wide-area deployments in everyday environments are still extremely rare. To deploy indoor locating systems beyond laboratory use, we believe that the initial configuration cost of the system should be reduced. This paper describes a fully distributed ultrasonic positioning system which enables us to locate various indoor objects with lower initial configuration cost.

A Novel Wireless Wake-Up Mechanism for Energy-Efficient Ubiquitous Networks

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.

Magic Surfaces: A Smart Building Material for Indoor Sensing Infrastructures

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.

Smart Baton System: a universal remote control system in ubiquitous computing environment

This paper describes a universal remote control system - Smart Baton System. This system enables users to explicitly and easily choose an appliance with a laser pointer, and provides users with an appropriate user interface that is customized for each appliance. Furthermore, with user authentication, this system allows an appliance to provide differentiated service to each user.

NGN/IMS-Based Ubiquitous Health Monitoring System

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.

A Ubiquitous Power Management System to Balance Energy Savings and Response Time Based on Device- level Usage Prediction

Power conservation has become a serious concern during peoples daily life. Ubiquitous computing technologies clearly provide a potential way to help us realize 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 precisely 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. Preliminary results demonstrate that Gynapse has the capability to reduce power consumption while keeping the response time within users requirement, and provides a complementary approach to previous power management systems.

A quantitative error analysis of synchronized sampling on wireless sensor networks for earthquake monitoring

Wireless sensor network technology enables low-cost and high-density earthquake monitoring. The earthquake monitoring measures structural vibrations caused by earthquakes. The earthquake monitoring contributes the progress of earthquake engineering and earthquake resistant technology. If we acquire high quality vibration data, we can precisely estimate structural damage. However, the high quality sensing is difficult because of the distribution manner of wireless sensor networks. In [3], we described overview of our earthquake monitoring. In this paper, we focus on a synchronized sampling mechanism in the earthquake monitoring: especially, its design and evaluation. Section 2 discusses what kind of factors cause sensing error in wireless sensor networks, Section 3 propose a synchronized low-jitter sampling mechanism, which minimize sensing error, and Section 4 evaluates the synchronized lowjitter sampling using a shaking table. Finally, Section 5 concludes this work.

Implementation-based approach for designing practical sensor network systems

Wireless sensor network technologies are expected to be a key technology to support various innovative applications in the future ubiquitous computing environment. So far, the mainstream of sensor network research has been focused on simulation-based development of battery-aware communication protocols. However, when we apply sensor network technologies to practical applications such as environmental monitoring or factory automation, we find a lot of practical problems that are not considered in simulation-based approach. We believe that finding and solving such practical problems are quite important for deploying sensor network technologies beyond laboratory use. From this point of view, we have been trying to find such problems through various implementations of sensor network system for several years. This paper describes our opinions of designing sensor network system and introduces our approaches for developing practical systems.

Spectrum sensor for distributed spectrum sensing

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.