Abstract: Train power lines provide a readily available and easily accessible network for measurement and control of unit communications within trains. The communication characteristics of passenger train power line channels are analyzed and found to suffer from highly variable, changing, and unpredictable signal to noise ratios. Power line transceivers usually operate in environments containing both background and strong impulse noise. To reduce the effects of the power noise and interference, a power line spread spectrum carrier communication system using digital pulse interval modulation (SSC DPIM) is proposed. In the system, a swept frequency spread spectrum carrier is used to generate pulses of the DPIM. A mathematical model to describe the signaling and the data transmission rate of the SSC DPIM system is given. The error ratio performance of the SSC DPIM system is compared with that of the established techniques of power line communications using both theoretical analysis and experimental results. The SSC DPIM transceiver is implemented by a micro processor and used successfully in a train fault monitoring system based on power line communications. In the monitoring system, the running parameters of trains such as axle temperature, miles operated, power load, sensor states and so on, are measured on the spot and transmitted into a train signal monitoring center simultaneously by power line channels.

Key words: spread-spectrum communication, power line communication, measure of fault