In-vehicle communication system and transmission path evaluation method

A transmission path evaluation method in an in-vehicle communication system including a plurality of communication transmission paths equipped in a vehicle, a first electronic device, and a plurality of second electronic devices communicably connected with the first electronic device by the communication transmission paths, wherein:

• each of the second electronic devices is communicably connected directly with the first electronic device by one of the communication transmission paths, or is communicably connected indirectly with the first electronic device through some of the communication transmission paths and another of the second electronic devices;
• and
• the transmission path evaluation method includes
• a step of sending, by a first processor of the first electronic device, a predetermined evaluation signal to a target device that is one of the second electronic devices,
• a step of receiving, by a transceiver of the second electronic device that is the target device, the evaluation signal from the first electronic device, and folding back a propagation direction of the evaluated signal and sending the evaluated signal back as a reply signal to the first electronic device,
• a step of receiving, by the first processor, the reply signal sent back by the second electronic device that is the target device, and evaluating a transmission quality of one or some of the communication transmission paths, the one or some of the communication transmission paths being provided from the first electronic device to the target device, and
• a step of storing, by the first processor, an evaluation result about the transmission quality, in association with the second electronic device that is the target device, wherein
• the communication transmission paths, the first electronic device and the plurality of second electronic devices constitute a communication network, the first electronic device and the plurality of second electronic devices being connected with each other by the communication transmission paths;
• and
• the first processor evaluates the transmission quality along a communication route from the first electronic device to the second electronic device at an end of the communication network, while sequentially adopting, as the target device, each second electronic device from the second electronic device at the end to the second electronic device closest to the first electronic device, and by comparing evaluation results with each other, determines whether the transmission quality of each communication transmission path included in the communication route is high or low.