Abstract: The present invention comprises a communication means 10 that receives a packet; a detection means 20 that detects information, contained in the packet, that is known to both transmitting-side and receiving-side communication apparatuses; a comparison means 30 that compares multiple pieces of the known information detected by the detection means 20; a channel estimation means 40; a demodulation means 60; and a control means 70. In the case where it has been determined, as a result of the comparison performed by the comparison means 30, that the multiple pieces of known information are different, the control means 70 makes a channel estimation start instruction to the channel estimation means 40 and makes a channel estimation packet send request to a communication apparatus that sent the packet via the communication means 10, and the channel estimation means 40 performs channel estimation using the sent channel estimation packet based on the channel estimation start instruction from the control means 70.