Shinichi Ishiko

Measurement and analysis of impulsive noise on in-vehicle power lines

In-vehicle signal transmission requires dedicated communication cables such as twisted metal wires and optical fiber cables, which increase the weight and the volume of wiring harnesses in vehicles. Furthermore, the number of electronic control units (ECUs) and the other electronic devices in vehicles is increasing. As a result, in-vehicle networks are becoming more and more complex and unstable. In-vehicle power line communication (PLC) system has been proposed to carry out signal transmissions between ECUs via in-vehicle power lines. The in-vehicle PLC system simplifies in-vehicle networks and reduces the weight and the volume of wiring harnesses. To design communication systems, we analyze communication environments which are mainly characterized by propagation channels and additive noise. In this paper, the measurement and the analysis of frequency responses for in-vehicle power lines are presented to analyze the propagation channels. Thus we observe frequency-selective fading channels which have several notches in the frequency domain because of reflection of signals at impedance mismatching points.We also analyze the noise and the interference in order to design reliable communication systems. For this purpose, the measurement and analysis of the noise on in-vehicle power lines are presented. A lot of bursty impulsive noises are observed while actuators in vehicles are active. A time-frequency analysis is applied to the observed noise and we show time-varying frequency spectra of the observed noise. Finally, we discuss in-vehicle PLC schemes which are suitable for signal transmissions.

Statistical impulse detection of in-vehicle power line noise using hidden Markov model

Control signal networks in vehicles using dedicated communication cables such as twisted wires and fiber optics cables have been built in order to communicate between electronic control units (ECUs). However, there are problems such as the increase in weight of the cable harness and the difficulty to insure the reliability of complicated network architectures. Communication systems using in-vehicle power lines have been investigated. This paper proposes an impulse detection scheme and its four criteria to decide the impulse occurrence in a communication cycle by using the two-state hidden Markovian-Gaussian noise model for noise on in-vehicle power lines. The new scheme involves the maximum a posteriori (MAP) estimation using the Baum-Welch (BW) algorithm and the moment method to estimate the model parameters. The proposed scheme is applied to noise generated from the hidden Markov model and noise observed on in-vehicle power lines and investigate their detection accuracy. It is shown that the detection accuracy is substantially improved by using an impulse occurrence criterion based on the number of free parameters.

Low rate and high reliable modulation schemes for in-vehicle power line communications

In-vehicle signal transmission requires dedicated communication cables such as twisted metal wires and optical fiber cables, which increase the weight and volume of wiring harnesses in vehicles. Low rate in-vehicle power line communication (PLC) systems are investigated to communicate the control data between electronic control units (ECUs) via in-vehicle power lines. To design low rate in-vehicle PLC systems, the communication channels are analyzed. It is shown that the channels are mainly characterized by frequency selective attenuation and narrowband impulsive noise. In this paper, a model of impulsive noise is presented for in-vehicle PLC and effects of carrier frequency selection and analog limiter on narrowband impulsive noise channels are analyzed in binary phase shift keying (BPSK), differential BPSK (DBPSK), and on-off keying (OOK). The simulation results show that DBPSK and differential detection with hard limiter achieve high reliable and cost-effective communications for low rate in-vehicle PLC systems.

High Rate and High Multiplexing CAN by Short Pulse Line Codes

Controller area network (CAN) is one of communication standards for in-vehicle control networks and enables electronic control units (ECU) to communicate various control commands with each other via a CAN bus. It is currently expected to develop CAN with higher rate and higher multiplexing, but the communication may be disabled by inter-symbol interference (ISI) due to ringing. In this paper, short pulse line codes and their symbol detection by weighted majority decision are proposed to achieve CAN with higher rate and higher multiplexing. A network structure is extracted as an evaluation network, which has large ringing duration by analyzing the transmission characteristics. The numerical analysis on received signals shows that the proposed schemes achieve sufficiently high reliability in the evaluation network. A prototype ECU implementing the proposed schemes provide successful communication links which are disabled in the conventional ECU.