A wireless communication system includes a plurality of base stations, a mobile wireless communication device which makes wireless communication with the base stations, a terminal device, and a router through which the base stations make communication with an IP network. The terminal device transmits an address thereof to the mobile wireless communication device, before the mobile wireless communication device makes link with one of the base stations. The terminal device fabricates a frame addressed to an address of the router, and transmits the frame to the router, after the mobile wireless communication device has made link with one of the base stations. The router transmits an address thereof to the base stations, before the mobile wireless communication device makes link with one of the base stations. The router fabricates a frame addressed to an address of the terminal device, and transmits the frame to the terminal device, after the mobile wireless communication device has made link with one of the base stations.