IN-VEHICLE COMMUNICATION DEVICE, IN-VEHICLE RELAY DEVICE, IN-VEHICLE COMMUNICATION SYSTEM AND COMMUNICATION METHOD

An in-vehicle communication system includes an in-vehicle communication device having a stream database and multiple in-vehicle relay devices connected to the in-vehicle communication device. Each in-vehicle relay device is connected to multiple in-vehicle control devices. The in-vehicle communication device and the in-vehicle relay device communicate with each other in a first communication protocol. The in-vehicle relay device and the in-vehicle control devices communicate with each other in a second communication protocol. The in-vehicle communication device stores time-series information received from the in-vehicle relay device in the stream database, and delivers the information stored in the stream database to the in-vehicle relay device. The in-vehicle relay device receives information delivered from the in-vehicle communication device and transmits it to the in-vehicle control devices and receives information transmitted from the in-vehicle control devices and transmits it to the in-vehicle communication device to store the information in the stream database.