COMMUNICATION SYSTEM AND COMMUNICATION DEVICE

摘要

PROBLEM TO BE SOLVED: To impede execution of a relay attack.SOLUTION: An on-vehicle communication device transmits authentication request signals including setting information concerning a division method of response signals and a transmission frequency of each segment of the response signals, to a portable apparatus. The portable apparatus divides the response signals into segments SG1 to SG4 on the basis of the received setting information and changes the transmission frequency by segment. The on-vehicle communication device changes a reception frequency according to the transmission frequency of each segment of the response signals. Also, the on-vehicle communication device combines the received segments to determine whether the combined response signals are proper signals. The invention can be applied to a vehicle communication system.