Nobuo Kawaguchi

Performance Evaluation of H. 264 Video Streaming over Inter-Vehicular 802.11 Ad Hoc Networks

This paper evaluates the performance of video streaming in inter-vehicular environments using the 802.11 ad hoc network protocol. We performed transmission experiments while driving two cars equipped with 802.11b standard devices in urban and highway scenarios. Different sequences, bitrates and packctization policies have been tested. The experiments show that each scenario presents peculiar characteristics in terms of average link availability and SNR, which can be exploited to develop more efficient applications. In this paper we also determine the best packetization policies for the two scenarios, showing that large packets lead to better performance in the highway scenario and vice versa. Perceptual quality results indicate that the best packetization policy achieves consistent gains in terms of PSNR values (up to 5 dB), and reduced quality variations, with respect to a fixed-policy transmission technique

Bayesian based location estimation system using wireless LAN

Over the last few years, wireless LAN and location-based service has been a hot subject of controversy. In this paper, we propose a Bayesian-based location estimation system and a location-based application using existing wireless access points at a college campus. Our system uses signal strength of access points and a Bayesian inference to estimate a users location. Using this pre-observation model-based system and considering signal strength direction, a user can construct a location estimation system easily and obtain good location estimation accuracy. Furthermore, our system allows users to know his/her location whenever they want without beacons searched by a system administrator or an unknown person. We implemented the system and exemplified its effectiveness with experiments at our campus. Using this system, we also propose a location-based presence service system. By using this presence system, one can get the location of friends automatically.

Indoor positioning method integrating pedestrian Dead Reckoning with magnetic field and WiFi fingerprints

In this paper, we propose a high accuracy indoor positioning method that uses residual magnetism in addition to Pedestrian Dead Reckoning (PDR) and WiFi-based localization methods. Our proposed method needs WiFi and magnetic field fingerprints, which are created by measuring in advance the WiFi radio waves and the magnetic field in the target map. The fingerprints are represented by a Gaussian Mixture Models (GMMs) to reduce the amount of computation. Our proposed method estimates positions by comparing the pedestrian sensor and fingerprint values by particle filters. We evaluated this method in real environments and confirmed that it provides accurate indoor positioning with a mean error less than 8 m and more accurate position detection than existing techniques.

Multimedia Corpus of In-Car Speech Communication

An ongoing project for constructing a multimedia corpus of dialogues under the driving condition is reported. More than 500 subjects have been enrolled in this corpus development and more than 2 gigabytes of signals have been collected during approximately 60 minutes of driving per subject. Twelve microphones and three video cameras are installed in a car to obtain audio and video data. In addition, five signals regarding car control and the location of the car provided by the Global Positioning System (GPS) are recorded. All signals are simultaneously recorded directly onto the hard disk of the PCs onboard the specially designed data collection vehicle (DCV). The in-car dialogues are initiated by a human operator, an automatic speech recognition (ASR) system and a wizard of OZ (WOZ) system so as to collect as many speech disfluencies as possible.In addition to the details of data collection, in this paper, preliminary results on intermedia signal conversion are described as an example of the corpus-based in-car speech signal processing research.

Position estimation of wireless access point using directional antennas

In recent years, wireless LAN technologies have experienced unprecedented growth, and new services and problems have occurred. In this paper, we propose a position estimation technique using directional antennas to assist the detection of wireless access points. Using an asymmetric model for estimation, our technique can radicalize probability distribution quicker than using a symmetric model. Our technique consists of three steps. The first measures the current position of the user, the direction of the antenna and the received signal strength of a target wireless access point. The second step estimates the position of the wireless access point from measured data using a signal strength model based on directivity. And the final step presents estimated results that assist the user. These steps are repeated for real-time assistance. We also conducted an evaluation experiments to clarify the effectiveness of our proposed technique.

MAGNET: ad hoc network system based on mobile agents

This paper proposes an ad hoc network system based on mobile agents. We regard some special mobile agent as an implementation of the network protocol. Mobile agents can move over the network while being carried by protocol agents. Implementation of the protocols by the mobile agents enables the dynamic extension of the network. We introduce agent replication for the simple development of the inter-agent communication. Agent hierarchy enables the component software design. We also describe the implementation of the ad hoc network protocol DSR using our prototype system MAGNET that is based on the framework.

HASC2011corpus: towards the common ground of human activity recognition

Human activity recognition through the wearable sensor will enable a next-generation human-oriented ubiquitous computing. However, most of research on human activity recognition so far is based on small number of subjects, and non-public data. To overcome the situation, we have gathered 4897 accelerometer data with 116 subjects and compose them as HASC2011corpus. In the field of pattern recognition, it is very important to evaluate and to improve the recognition methods by using the same dataset as a common ground. We make the HASC2011corpus into public for the research community to use it as a common ground of the Human Activity Recognition. We also show several facts and results of obtained from the corpus.

Underground Positioning: Subway Information System Using WiFi Location Technology

We introduce a subway information system which utilize WiFi location technology for supporting a person in the underground. The system is composed of a mobile terminal with a WiFi device and a communication server. We have developed seven location aware applications for the mobile terminal. Each of the application helps the user with current location information. We have performed a demonstration experiment in the subway of Nagoya City with 35 subjects and got a positive acceptance of the system.

WiFi Location Information System for Both Indoors and Outdoors

We introduce a location information system for both indoors and outdoors which utilize WiFi location technology. The system is composed of a mobile terminal with a WiFi device and a communication server. We have developed seven location aware applications for the mobile terminal. Each of the application helps the user with current location information. We have performed a demonstration experiment in the subway of Nagoya City with 35 subjects and got a positive acceptance of the system.

NEXCESS: Nagoya university extension courses for embedded software specialists

In October 2004, Nagoya University has started an extension program on embedded software, called NEXCESS (Nagoya university EXtension Courses for Embedded Software Specialists). NEXCESS aims at education of engineers in industry, and is financially supported by the government. This paper describes the organization and course design of NEXCESS. Also, our experience of the first half year is reported.