鉄道信号システムの高機能化を実現する伝送方式の検討

概要

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Railway signaling systems that transmit control information via rails have been deployed in many applications, for example, digital automatic train control (ATC) systems for controlling train speed. Since the performance of digital ATC systems depends on the signal transmission speed, recently there have been many studies aimed at realizing high-speed data transmission. However, it is difficult to increase the transmission speed because rails have strong attenuation in proportion to an increase of the frequency. In this paper, we aimed to increase the transmission speed by improving the modulation scheme to overcome these limitations. We proposed CDMA-QAM method that is combined code-division multiple access (CDMA) and quadrature amplitude modulation (QAM). And we evaluated in a field trial the CDMA-QAM rail transmission device developed using DSP. On the other hand, an analog ATC based on an amplitude modulation (AM) is still employed in some railway lines. It is difficult for their lines to introduce the digital signal due to track circuit configurations and interoperability conditions. So we studied a data transmission scheme that makes it possible to mix an analog signal and a digital signal, and evaluated the influence given to both signals using a developed device that generates the mixed signal of analog and digital signal.