On-vehicle communication device
An on-vehicle communication device capable of suppressing a delay in providing information, avoiding congestion, and sufficiently securing transmission power, includes a communication controller to controls a transmission cycle and transmission power when data is transmitted from a transmitting/receiving device. The communication controller uses its own vehicle information and surrounding vehicle information to estimate a degree of risk and a safe distance of its own vehicle. The communication controller controls the transmission cycle of its own vehicle based on a communication channel utilization rate of its own vehicle, a communication channel utilization rate of a surrounding vehicle and the degree of risk of its own vehicle, and controls the transmission power of its own vehicle based on the communication channel utilization rate of its own vehicle, the communication channel utilization rate of the surrounding vehicle and the safe distance.
1. An on-vehicle communication device mounted on a first vehicle and wirelessly communicating with at least one second vehicle other than said first vehicle, comprising:
a transmitter/receiver configured to obtain a first communication channel utilization rate indicating a time rate at which a radio wave field intensity of a predetermined level or more in said first vehicle is received and to receive from said second vehicle, second vehicle information regarding running of said second vehicle and a second communication channel utilization rate indicating a time rate at which a radio wave field intensity of a predetermined level or more in said second vehicle is received; and
communication control means controlling a first vehicle transmission cycle and first vehicle transmission power when data is transmitted from said transmitter/receiver,
wherein said communication control means controls said first vehicle transmission cycle based on said first communication channel utilization rate and said second communication channel utilization rate to increase the first transmission cycle if said first channel communication rate is equal to or higher than a certain level and to decrease said first transmission cycle if said first channel communication rate is equal to or lower than a second level and within a certain range, so as to converge on a target communication channel utilization rate.
2. The on-vehicle communication device according to claim 1 , wherein:
said communication control means controls said first vehicle transmission cycle based on a maximum communication channel utilization rate of said first communication channel utilization rate and said second communication channel utilization rate.
3. The on-vehicle communication device according to claim 2 , wherein said communication control means controls said communication channel utilization rate to a predetermined communication channel utilization rate by feedback control of said first vehicle transmission power, based on said communication channel utilization rate.
4. The on-vehicle communication device according to claim 1 , wherein:
said communication control means:
estimates a first degree of risk indicating a degree of risk of said first vehicle using first vehicle information and said second vehicle information, the first vehicle information being obtained from said first vehicle and relating to running of said first vehicle; and
controls said first vehicle transmission cycle by weighting based on said first degree of risk.
5. The on-vehicle communication device according to claim 1 , wherein said communication control means:
estimates a safe distance required for performing deceleration to a predetermined speed or stop using said first vehicle information and said second vehicle information; and
controls said first vehicle transmission power based on said safe distance.
6. The on-vehicle communication device according to claim 4 , wherein:
said transmitter/receiver further receives a second degree of risk indicating a degree of risk of said second vehicle from said second vehicle; and
said communication control means controls said first vehicle transmission cycle further based on said second degree of risk.
7. The on-vehicle communication device according to claim 4 , further comprising data generating means generating, at a predetermined timing, transmission data including at least said first vehicle information, said first communication channel utilization rate and said first degree of risk,
wherein said transmitter/receiver transmits said transmission data generated by said data generating means under control of said communication control means.
8. The on-vehicle communication device according to claim 1 , wherein:
said first vehicle information includes position information of said first vehicle;
said second vehicle information includes position information of said second vehicle; and
said communication control means:
calculates a relative distance between said first vehicle and said second vehicle from said position information of said first vehicle and said position information of said second vehicle; and
controls said first vehicle transmission power further based on said relative distance.
9. The on-vehicle communication device according to claim 8 , wherein said communication control means controls said first vehicle transmission power further based on map information set in advance.
10. The on-vehicle communication device according to claim 1 , wherein:
said first vehicle information includes acceleration information of said first vehicle; and
said communication control means controls said first vehicle transmission power further based on the acceleration information of said first vehicle and map information set in advance.