A source terminal measures characteristics of the path at the source terminal itself, produces a characteristics-measurement packet, and transmits the produced characteristics-measurement packet to a relay terminal. Upon receiving the characteristics-measurement packet, the relay terminal measures characteristics of the path at the relay terminal itself, renews the characteristics of the path included in the characteristics-measurement packet using the measured characteristics of the path, and transmits the characteristics of the wireless communication path to the destination terminal. The source terminal produces an admission-request packet and transmits the packet to the destination terminal. Upon receiving the admission-request packet, the destination terminal allows or rejects the traffic quality maintenance request according to the characteristics of the wireless communication path. The allowance or rejection of the quality maintenance request is transmitted to the source terminal with the admission-reply packet by the destination terminal.