Predicted future positions are calculated (S11) and arranged into packets
(S12) to be transmitted using a communication pattern (for example, a PN
series) based on a time and a position of each packet (S13). Another
vehicle calculates its predicted position (S21) and generates a
communication pattern based on a result of calculation (S22) so that the
generated communication pattern is utilized for reception (S23).
Consequently, data associated with a future position of its own can be
selected for enabling reception. An existence probability is calculated,
and the state of another vehicle can be accurately understood from the
communication of the calculated existence probability, thereby effectively
reducing chance of collision.
