Kazumasa Ushiki

A new handover method for next generation mobile communication systems

The next generation mobile communication systems, such as the International Mobile Telecommunication-2000 (LMT-2000), will introduce new technologies and services including broadband communications, soft-handovers, micro/pico cell architecture, and multicall/connection services. In this paper, we first clarify the impact of these new technologies and services on handover performance. We then propose a new handover method, in which the handover connection setup process is divided into the network connection setup and the radio connection setup parts, with the former taking place before a handover request by predicting the next cell.

Quality analysis of CSMA/CA communications in inter-vehicle communication services

Recently, inter-vehicle communication services which support safe driving have been attracting significant. CSMA/CA is a representative communication method in inter-vehicle communications. It is necessary to clarify the quality characteristics of inter-vehicle communication in order to achieve driving support. Although there are conventional models for CSMA/CA which are derived using an ideal environment, they are not consistent with behavior in actual inter-vehicle communication. This paper proposes a mathematical model that can analyze communication quality between the specific vehicles by dealing with the discrepancies between conventional theory and practice. Furthermore, we analyze communication performance between vehicles in specific accidents using the proposed model.