Onboard communication apparatus and control method thereof

A control method of an onboard communication apparatus that is installed in a vehicle and that performs communication with a roadside communication apparatus that provides various data and performs communication with other onboard communication apparatuses that are installed in other vehicles, comprising:

• setting a channel whose frequency band is fixed in a first communication unit and setting a channel that differs from the channel that is used in said first communication unit in a second communication unit;
• communicating with said roadside communication apparatus by way of said first communication unit or said second communication unit;
• determining whether or not communication with said roadside communication apparatus is direct communication that is not relayed by another onboard communication apparatus;
• and
• when not performing direct communication with said roadside communication apparatus, said second communication unit communicates with said roadside communication apparatus by way of another onboard communication apparatus that is communicating with said roadside communication apparatus.