| 摘要 |
PROBLEM TO BE SOLVED: To decrease the number of vehicles that postpone transmission and the number of vehicles where transmitted packets collide with each other within a period of updating vehicle information, resulting in most increasing number of vehicles where the packet transmission is successful. SOLUTION: In the case of setting a carrier sense time by a time-waiting type CSMA system in the inter-vehicle communication, when the result of carrier sensing by a carrier sense section 9 indicates that a channel is idle, its own vehicle information and its own vehicle ID are transmitted. In the case that a channel is busy as a result of carrier sensing, a total vehicle number estimate section 15 estimates number of vehicles making the inter-vehicle communication on the basis of number of other different vehicle IDs detected within a prescribed time, a carrier sense time setting section 8 sets a maximum time interval for carrier sensing on the basis of the number of vehicles above and a random time within the set maximum time is set as a succeeding carrier sensor time.
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