Tomotaka Nagaosa

An emergency earthquake warning system using mobile terminals with a built-in accelerometer

In this paper, we study an emergency earthquake warning system using mobile terminals with a built-in accelerometer. First, the earthquake warning system that uses mobile terminals such as smart phones as seismographs is proposed. When an earthquake occurs, the mobile terminals detect seismic wave using a built-in accelerometer. If the value of acceleration exceeds the threshold value, information of acceleration is transmitted to a server on each region. The server manages information that has been sent by mobile terminals, and presumes the seismic intensity and the hypocenter, and sends warning messages to user terminals around the server. Then we evaluate the server of the proposed system, and show the sending and receiving ability of warning messages.

An advanced CSMA inter-vehicle communication system using packet transmission timing decided by the vehicle position

We examine the performance of inter-vehicle communication (IVC) systems using the IEEE802.11b standard CSMA scheme and a proposed system in which packet transmission timing is decided by the vehicle position. For the realization of safety cruise-assist systems by IVC systems, the spread of transceivers on vehicles is important. To improve the equipped rate of transceivers on vehicles, it is necessary that the implementation of more simple and cheaper IVC systems. One of the solutions is using conventional wireless LAN systems for IVC systems. So we evaluate the performance of an IVC system using the conventional IEEE802.11b CSMA system. In addition, we propose and evaluate an improvement scheme for solving the performance degradation caused by packet collision. The results of simulation show that the proposed scheme is superior to other schemes when the bit rate is low. Also, it is shown that the proposed scheme has the same or higher performance than the other schemes in high bit rate.

Vehicle localization using its vibration caused by road surface roughness

This paper describes a study of vehicle localization using its vibration due to road surface roughness. The authors suggest a vehicle localization scheme in which a vehicle can identify its location on the road. The vehicle localization can be carried out matching the current vehicle vibration with the prior observed vehicle vibration in the database as a vibration map. In this paper, the longitudinal vehicle localization is carried out by observing the vehicle vibration with a smart phone on the dashboard. First, the authors examine the effect of the matching duration of the current vehicle vibration data to the prior observed vibration for the precise of vehicle localization. It is shown that the long duration matching is effective in more precise vehicle localization. Next, the authors evaluate the performance of the vehicle localization scheme using current vehicle vibration data and prior vibration data in the database observed from the same vehicle, and using the ones from a vehicle and the ones from another vehicle. It is shown that the vehicle localization error is about 2.5 meter when using vibration data from the same vehicle, and about 3.5 meter when using vibration data from a vehicle and another vehicle.

An emergency Earthquake warning system for land mobile vehicles using the earthquake early warning

This paper describes a study of an emergency earthquake warning system for land mobile vehicles using the Earthquake early warning in Japan, First, estimation accuracy of seismic wave is evaluated at a local area, when using both the position information and the soil information database in addition to the Earthquake early warning, and it is shown that using those additional information is effective for indication of the earthquake warning to each vehicle. Second, an emergency warning system for land mobile vehicles is proposed and the distribution system of the warning messages in the proposed system is investigated. It results that the Ground digital broadcasting is effective for the distribution to vehicles of the warning messages because of high quality and usability on mobile, and the Dedicated short range communication can also be provided reliable distribution. Last, an automotive experimental software of the proposed system is developed and confirmation of the software is performed by using warnings.

Self-similarities in transmission delay of CDMA cellular packet systems for varying transmission power control error

This paper discusses self-similarity in the uplink traffic of CDMA cellular packet communications. We estimate the Hurst parameter of transmission delay time, which is collected by using computer simulation, and analyze its power spectrum. We find that self-similarity and the 1/f power spectrum are observed in transmission delay time on the uplink of a CDMA cellular packet system. Self-similarity is also analyzed for various errors of transmission power control in order to discover the system conditions under which self-similarity appears. The results of these analyses show that the power control error has a large effect on the self-similarity: self-similarity appears in a system with an accurate power control, whereas it does not appear in a system with a large power control error.

A proposal of the rendezvous navigation system

This paper describes a proposal of the rendezvous navigation system which is used for meeting at any place, as a smartphone application. First, we propose the pedestrian navigation system for having a rendezvous with a companion without any map. The proposed system indicates the direction in which the companion is. This navigation application describes the arrow which indicates the direction of being the companion on a live view of real-world environment. The direction of the arrow decides the position information of itself and the companion which gets using GPS and exchanges each other using communication devices. Next, the examination for the performance evaluation of the proposed system was carried out in the campus of Kanto Gakuin University. Last, the improvement of the proposed application was tried based on a questionnaire survey.

An effect of applying information filtering to a positioning system using address information on Web and spot information in cityscape

This paper describes an effect of applying information filtering to the positioning system using address information on Web and spot information in cityscape. On the positioning procedure, the positioning system gets the search results which include address information of inputted spots from a Web search engine. The improved scheme is to apply the information filtering to the procedure, and can remove useless position information. To evaluate the improved system, the experiments of the system are carried out in an urban area. It is shown that accuracy of the improved system is superior to that of GPS and the conventional system.

Performance evaluation of a media access control scheme using vehicle position information for an inter-vehicle communication system

This paper describes a consideration of a media access control scheme based on CSMA using vehicle position information for an inter-vehicle communication (IVC) system in safety driving assist systems. IVC systems are demanded to perform the real-time and reliable communication among vehicles on the road from safety driving assist systems. The IVC system in this paper can communicate among vehicles without hidden terminal problems since vehicles on an area permits to access only a corresponding subframe to the area in time frame. The frame construction of the proposed IVC system is shown and is evaluated the performance of the proposed system via computer simulations.