Author(s)

K. Seki

Abstract

There are some cases when we would like to construct tentative communications systems easily along railway lines even if they cannot fully guarantee to satisfy transmission qualities. For example, we need to grasp situations of disasters or accidents which have happened at the place where not enough transmission bandwidths are secured or the transmission system itself has been damaged. Ad hoc network technologies are a candidate for constructing such tentative networks. Their standardizations are in progress and some commercial products are emerging. We carried out an experiment using commercial products which implemented a standardized protocol and constructed a network by wireless LAN, and confirmed that the network was easily constructed but frame loss rates and time to change routes when devices broke were insufficient for some cases. We, therefore, tentatively made telecommunications nodes which used both wired LAN and wireless LAN. We confirmed that a satisfying performance was obtained until about three wireless hops even if only wireless LAN was used, and transmissions continued even when a cable or the node was damaged. Keywords: ad hoc network, image transmission. 1 Introduction Railway telecommunications systems, such as train radio, are important infrastructures which support train operations. After they are minutely designed in order to satisfy requirements such as coverage areas and quality of services, fixed equipments such as wireless base stations, exchanges, and wired transmission lines which connect between them are installed. The systems can, therefore, maintain the required transmission qualities for a long time once they

Keywords

ad hoc network, image transmission.