We newly propose a protocol stack of a multiservice terminal that can handle conventional wireless communication systems as a seamless network. To confirm the feasibility of our proposed stack, we developed a demonstration system that realizes a seamless communication between Japanese Personal Handy Phone system (PHS) and wireless LAN system based on IEEE802.11b, and measured transmission characteristics included the received-signal power of the wireless LAN signal at the multiservice terminal, time-variant state of the multiservice terminal, and the response time when "ping" commands are sent to a server.