US Patent 7778222 Wireless IP telephone system

A wireless IP telephone system including a dynamic address lease server for leasing an IP address to each of terminals and a controller. The controller has information about the IP address, a SIP URI of the terminal, a type thereof, and a function thereof. The information of the controller is dynamically set by a system administrator who manually sets the information or by the dynamic address lease server and the controller which are cooperated. The controller decides an effective period of the address to be leased to each terminal, informs the dynamic address lease server of the fact, and requires the address lease server to release the address which became unnecessary.