Electronic communication system and signal transmission method

A signal transmission method in an electronic communication system in which a vehicle control unit and a higher-order control unit are connected through a lower-order communication line, and a plurality of the higher-order control units are connected to each other through a higher-order communication line, the vehicle control unit controlling a functional unit mounted in a vehicle, the signal transmission method comprising:

• causing the higher-order control unit to start up from a sleep state by the vehicle control unit transmitting a first wake-up signal to the higher-order control unit through the lower-order communication line;
• and
• by the higher-order control unit, determining a first transmission period, based on a time period required for another one of the higher-order control units to start up, the another higher-order control unit being connected to the higher-order control unit through the higher-order communication line, and transmitting a second wake-up signal to the another higher-order control unit at regular intervals of the determined first transmission period,
• wherein
• the signal transmission method further comprises, by the higher-order control unit:
• switching between and performing one of an ordinary start-up function and a high-speed start-up function, depending on a function that is a cause for the vehicle control unit to transmit the first wake-up signal;
• when performing the ordinary start-up function, transmitting the second wake-up signal at intervals of a predetermined second transmission period;
• and
• when performing the high-speed start-up function, determining the first transmission period that is different from the second transmission period, based on the time period required for the another higher-order control unit to start up.

An electronic communication system comprising:

• a vehicle control unit that controls a functional unit mounted in a vehicle;
• and
• a higher-order control unit, wherein
• the vehicle control unit and the higher-order control unit are connected through a lower-order communication line, and a plurality of the higher-order control units are connected to each other through a higher-order communication line, and
• the higher-order control unit starts up from a sleep state in response to receiving a first wake-up signal from the vehicle control unit through the lower-order communication line, determines a first transmission period, based on a time period required for another one of the higher-order control units to start up, the another higher-order control unit being connected to the higher-order control unit through the higher-order communication line, and transmits a second wake-up signal to the another higher-order control unit at regular intervals of the determined first transmission period,
• the higher-order control unit determines the first transmission period, based on the time period that was required for the another higher-order control unit to start up in past.