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In this paper, we propose a selective visible light communication method using a single light source and multiple video cameras by using their differences in reception sensitivity between carrier waves composed of OFDM signals. In our evaluation experiments, the transmitted signals were composed of 50th, 75th, 78th, and 80th order carrier waves encoding symbols modulated by 4, 8, and 16 PSK. The exposure time ratio for each camera was set to different values so that symbols encoded in one of the carrier waves could be decoded successfully, but erroneously in the other waves. The selectivity of individual carrier waves as theoretically derived was confirmed through the experimental results.

This paper describes a rapid and flicker-free visible light communication technique that uses an off-the-shelf video camera. Transfer rates at least 53% faster than existing methods were achieved in experiments. Features of the proposed method are discussed via theoretical analysis.

The paper describes a rapid and accurate time-synchronization technique for smartphones using their built-in cameras and its preliminary evaluations for application development.

In this paper, we present an indoor 3D positioning method for smartphones using acoustic signals. In our proposed 3D Frequency Division Multiplexing--Phase Accordance Method (3D FDM--PAM), four speakers simultaneously emit burst signals comprising two carrier waves at different frequencies to enable the rapid calculation of the position of the smartphone. Through experiments, we show that 3D FDM--PAM can achieve a standard deviation of less than 2.8 cm at 7.8 measurements per second. The worst positioning error was 48.3 cm at the 95th percentile. We investigate the causes of error and discuss potential improvements to the localization performance.

In recent years, mobile devices have rapidly penetrated into our daily lives. However, several drawbacks of mobile devices have been mentioned so far. The proposed system called Toss-It provides intuitive information transfer techniques for mobile devices, by fully utilizing their mobility. A user of Toss-It can send information from the user's PDA to other electronic devices with a toss or swing action, as the user would toss a ball or deal cards to others. This paper describes the current implementation of Toss-It and its user studies.

In this paper, a system called Caretta that integrates personal and shared spaces to support face-to-face collaboration is described. We use PDAs and a multiple-input sensing board for personal and shared spaces, respectively. Users of Caretta can discuss and negotiate with each other in the shared space by manipulating physical objects, while they individually examine their ideas in their own personal spaces. Caretta allows users to participate in group activities interchangeably and seamlessly using both these spaces. Caretta is applicable to various collaborative tasks. In this paper, it supports users in urban planning tasks. User studies of Caretta demonstrated that it allowed users to collaborate in a flexible fashion: users could work individually in their personal spaces at their own pace, cooperatively work together in the shared space, and smoothly transition between both of the spaces.

In this paper we describe our project to design a system that can be used as a teaching aid to support group learning in elementary school education. The system enhances the learning outcome for pupils who have studied environmental problems using a textbook, by allowing them to construct a town in a physical space and to assess the construction through computer simulations. The system was designed in collaboration with teachers and their pupils in elementary schools. Lessons learned from the collaborative design processes are described.